Search

Beginning with a large push from consumers to improve meat and carcass quality in the 1990s, through selection, the beef industry has successfully made significant genetic gains towards achieving these improvements. For producers looking to increase the genetic potential of their own herds for carcass quality there are multiple considerations that will inform the time it takes to see improvement. Some of the primary factors influencing the rate of genetic gain for carcass quality phenotypes include: 1) available selection candidates, 2) trait heritability, 3) selection accuracy, and 4) selection intensity. Using the Germplasm Evaluation beef herd at the US Meat Animal Research Center, many of the possible factors influencing this timeline have been evaluated. Collection of carcass quality phenotypes has been an ongoing, long-term objective of the project and has allowed for the estimation of trait heritabilities, breed differences, heterosis effects, and genetic trends over time for this trait complex. Additionally, this herd facilitated the development of decision support tools for creating selection indices and breeding programs, representing the culmination of many of these research outcomes. There are multiple ways to achieve genetic improvement for carcass quality, and our primary objective is to equip producers and other stakeholders with the necessary information to make informed selection decisions. The USDA is an equal opportunity provider and employer [ABSTRACT FROM AUTHOR]

Bos indicus-Bos taurus crosses have been effectively used in many production environments globally. Substantially higher amounts of hybrid vigor have been reported in these F1 crosses as compared with those involving only Bos taurus or only Bos indicus breeds. However, for many years, and in many environments, “unusual” aspects of calf growth have been documented among these crosses. Among F1 crosses, Bos indicus-sired calves (Bos indicus x Bos taurus) have birth weight 8 to 12 kg heavier than contemporary Bos taurus-sired calves (Bos taurus x Bos indicus); additionally, pronounced sexual dimorphism occurs where males may weigh 5 to 10 kg more than females from Bos indicus sires (Bos taurus dams) but 1 kg or less from Bos taurus sires (Bos indicus dams) in both natural service and embryo transfer calves. These reciprocal differences have been reported for fetal and placentome size mid gestation. Reciprocal differences in birth weight have also been reported among backcrosses and F2 calves, and also exist for longer gestation length from Bos indicus sires (Bos taurus dams). Increased birth weight and gestation length occur when more Bos indicus is present in the sire vs. the dam, and when Bos indicus influence is inherited through the sire vs. the dam. There is speculation that sex-specific genomic imprinting may be involved for reciprocal birth weight differences that are analogous to mouse interspecific crosses for litter weight. Reports of hybrid vigor retention among inter se matings after the F1 have been variable historically, and this variation may relate to how the foundational F1 parents were produced (Bos indicus- vs. Bos taurus-sired). Breed-of-origin haplotype on BTA5 has been shown to affect heifer pregnancy and rebreeding among F2 Nellore-Angus cows where Nellore-derived haplotypes had much lower performance compared with Angus-derived and hybrid haplotypes. Disproportionate calf sex has been reported among reciprocal F2 Nellore (Bos indicus)-Angus (Bos taurus) with 66.6% male calves from Nellore x Angus F1 sires. When retrospectively evaluating historical literature for reciprocal crosses, it appears that several instances occur with disproportionate calf sex percentage, and this phenomenon warrants further study. The extent that potential reciprocal differences may affect post-weaning growth and carcass traits has not been widely evaluated. Recent investigations have shown reciprocal F1 differences for some cell-mediated immune responses regarding T-lymphocyte proliferation, but no differences for humoral response. There needs to be additional research that completely characterizes the X chromosome of Bos indicus and Bos taurus origins and their roles for multiple production traits. There also needs to be more investigation of non-additive and parent-of-origin effects in genetic evaluations of Bos indicus-Bos taurus composites, particularly with desired first-generation breed percentage. Improved utilization of Bos indicus cattle and crosses will be instrumental in meeting global dietary protein demands. [ABSTRACT FROM AUTHOR]

Crossbreeding is a common practice among commercial sheep producers to improve animal performance. However, genetic evaluation of U.S. sheep is performed within breed type (terminal sire, semi-prolific, and western range). While incorporating crossbred records may improve assessment of purebreds, it requires accounting for heterotic and breed effects in the evaluation. The objectives of this study were to: 1) describe the development of a paternal composite (PC) line, 2) determine the effect of direct and maternal heterosis on growth traits of crossbred lambs, 3) estimate (co)variance components for direct and maternal additive, and uncorrelated maternal environmental, effects, and 4) provide an interpretation of the estimates of random effects of genetic groups, and to use those solutions to compare the genetic merit of founding breed subpopulations. Data included purebred and crossbred records on birth weight (BN; n = 14,536), pre-weaning weight measured at 39 or 84 d (WN; n = 9,362) depending on year, weaning weight measured at 123 d (WW; n = 9,297), and post-weaning weight measured at 252 d (PW; n = 1,614). Mean (SD) body weights were 5.3 (1.1), 16.8 (3.9) and 28.0 (7.6), 39.1 (7.2), and 54.2 (8.7) kg for BN, WN (at the two ages), WW, and PW, respectively. In designed experiments, the Siremax, Suffolk, Texel, Polypay, Columbia, Rambouillet, and Targhee breeds were compared within the same environment. Estimates of heterotic effects and covariance components were obtained using a multiple trait animal model. Genetic effects based on founders' breeds were significant and included in the model. Percent estimates of direct heterosis were 2.89 ± 0.61, 2.60 ± 0.65, 4.24 ± 0.56, and 6.09 ± 0.86, and estimates of maternal heterosis were 1.92 ± 0.87, 4.64 ± 0.80, 3.95 ± 0.66, and 4.04 ± 0.91, for BN, WN, WW, and PW, respectively. Correspondingly, direct heritability estimates were 0.17 ± 0.02, 0.13 ± 0.02, 0.17 ± 0.02, and 0.46 ± 0.04 for BN, WN, WW, and PW. Additive maternal effects accounted for trivial variation in PW. For BN, WN, and WW, respectively, maternal heritability estimates were 0.16 ± 0.02, 0.10 ± 0.02, and 0.07 ± 0.01. Uncorrelated maternal environmental effects accounted for little variation in any trait. Direct and maternal heterosis had considerable impact on growth traits, emphasizing the value of crossbreeding and the need to account for heterosis, in addition to breed effects, if crossbred lamb information is included in genetic evaluation. [ABSTRACT FROM AUTHOR]

Understanding the genetic relationship between mature cow weight (MWT) and body condition score (BCS) is useful to implement selection programs focused on cow efficiency. The objectives of this study were to estimate genetic parameters, heterosis, and breed effects for MWT and BCS. In total, 25,035 and 24,522 overlapping records were available for MWT and BCS on 6,138 and 6,131 cows, respectively, from the Germplasm Evaluation program, a crossbred beef population at the U.S. Meat Animal Research Center. Pedigree was available for 48,013 individuals. Univariate animal models were used to estimate heritabilities for each trait by parity. Bivariate animal models were used to estimate genetic correlations between parities within a trait and between traits within parities. Bivariate repeatability animal models were used to estimate genetic correlations between traits across parities. Estimates of heritability for different parities ranged from 0.43 ± 0.05 to 0.55 ± 0.07 for MWT and from 0.12 ± 0.03 to 0.25 ± 0.04 for BCS and were lower with the repeatability model at 0.40 ± 0.02 and 0.11 ± 0.01 for MWT and BCS, respectively. Estimates of repeatability were high for MWT (0.67 ± 0.005) and low for BCS (0.22 ± 0.006). Estimates of genetic correlation for MWT and BCS between parities were, in general, high, especially between consecutive parities. Estimates of genetic correlation between MWT and BCS were positive and moderate, ranging from 0.32 ± 0.09 to 0.68 ± 0.14. The direct heterosis estimates were 21.56 ± 3.53 kg (P ≤ 0.001) for MWT and 0.095 ± 0.034 (P ≤ 0.001) for BCS. Ordered by decreasing MWT, the breeds ranked Brahman, Charolais, Angus, Simmental, Salers, Hereford, Santa Gertrudis, Chiangus, Brangus, Red Angus, Shorthorn, Maine-Anjou, Gelbvieh, Beefmaster, Limousin, and Braunvieh. Ordered by decreasing BCS, the breeds ranked Brahman, Red Angus, Charolais, Angus, Hereford, Brangus, Beefmaster, Chiangus, Salers, Simmental, Maine-Anjou, Limousin, Santa Gertrudis, Shorthorn, Gelbvieh, and Braunvieh. Estimates of breed differences for MWT were also adjusted for BCS (AMWT), and in general, AMWT depicted smaller differences between breeds with some degree of re-ranking (r = 0.59). These results suggest that MWT and BCS are at least moderately genetically correlated and that they would respond favorably to selection. Estimates of breed differences and heterotic effects could be used to parameterize multibreed genetic evaluations for indicators of cow maintenance energy requirements. [ABSTRACT FROM AUTHOR]

Cow mature weight (MWT) is heritable and affects the costs and efficiency of a breeding operation. Cow weight is also influenced by the environment, and the relationship between the size and profitability of a cow varies depending on production system. Producers, therefore, need tools to incorporate MWT in their selection of cattle breeds and herd replacements. The objective of this study was to estimate breed and heterotic effects for MWT using weight-age data on crossbred cows. Cow’s MWT at 6 yr was predicted from the estimated parameter values—asymptotic weight and maturation constant (k)—from the fit of the Brody function to their individual data. Values were obtained for 5,156 crossbred cows from the U.S. Meat Animal Research Center (USMARC) Germplasm Evaluation Program using 108,957 weight records collected from approximately weaning up to 6 yr of age. The cows were produced from crosses among 18 beef breeds. A bivariate animal model was fitted to the MWT and k obtained for each cow. The fixed effects were birth year-season contemporary group and covariates of direct and maternal breed fractions, direct and maternal heterosis, and age at final weighing. The random effects were direct additive and residual. A maternal additive random effect was also fitted for k. In a separate analysis from that used to estimate breed effects and (co)variances, cow MWT was regressed on sire yearling weight (YWT) Expected Progeny Differences by its addition as a covariate to the animal model fitted for MWT. That regression coefficient was then used to adjust breed solutions for sire selection in the USMARC herd. Direct heterosis was 15.3 ± 2.6 kg for MWT and 0.000118 ± 0.000029 d−1 for k. Maternal heterosis was −5.7 ± 3.0 kg for MWT and 0.000130 ± 0.000035 d−1 for k. Direct additive heritabilities were 0.56 ± 0.03 for MWT and 0.23 ± 0.03 for k. The maternal additive heritability for k was 0.11 ± 0.02. The direct additive correlation between MWT and k was negligible (0.08 ± 0.09). Adjusted for sire sampling, Angus was heaviest at maturity of the breeds compared. Deviations from Angus ranged from −8.9 kg (Charolais) to −136.7 kg (Braunvieh). Ordered by decreasing MWT, the breeds ranked Angus, Charolais, Hereford, Brahman, Salers, Santa Gertrudis, Simmental, Maine Anjou, Limousin, Red Angus, Brangus, Chiangus, Shorthorn, Gelbvieh, Beefmaster, and Braunvieh. These breed effects for MWT can inform breeding programs where cow size is considered a key component of the overall profitability. [ABSTRACT FROM AUTHOR]

Escalating impacts of climate change present a credible threat to livestock-based food production. Increasing environmental challenges directly affect animal fitness, production performance, and reproductive efficiency with accumulative morbidities and mortality. Albeit extant livestock breeds are adapted to different climate extremes, the steep trajectory of decline in genetic diversity poses a serious threat to the sustenance of livestock farming. After pluripotent stem cells (PSCs) were derived for mice more than 30 years ago, scientists were quick to recognize PSCs as an approach to accelerate livestock biotechnology and assisted reproduction. We posited that core PSC characteristics such as indefinite self-renewal make them ideal for setting up an inexhaustible diploid livestock genetic resource bank. Nevertheless, it has been difficult to derive and sustain naïve PSCs from ruminants. Even reports of generating induced-PSCs (iPSCs) via reprogramming somatic cells that circumvents the embryo and factors such as sex, age or reproductive status, has been crippled with reproducibility issues precluding any livestock applications. In recent systematic studies, we documented two roadblocks: First, that signaling pathways necessary to sustain self-renewal of PSCs from cattle remained unknown. Second, bovine somatic cells have a stable epigenome that is resistant to complete reprogramming to pluripotency. Through systems biology examination of signal homeostasis in the bovine blastocyst inner cell mass (ICM), we uncovered that transforming growth factor (TGF) ß effects are actively perturbed in the bovine ICM. This led to the discovery that inhibition of downstream ALK 4/5/7 together with GSK3ß and MEK1/2 signaling, supported robust in vitro self-renewal of naïve bovine iPSCs. Simultaneously, we uncovered that epigenetic regulation by the SV40 large T antigen together with the reprogramming genes (OCT4, SOX2, KLF4 and MYC) could result in not only complete reprogramming, but also cells that are set to a stable ground state of pluripotency akin to totipotent stem cells (TPSCs) seen in 16-cell-stage bovine embryos. Cloning performed using the induced TPSCs (iTPSCs) showed significantly greater efficiency of blastocyst formation. Surprisingly, applying identical methods to murine somatic cells also resulted in iTPSCs that can contribute to placenta formation in vivo indicating that the mechanistic basis for sustaining the ground state of developmental plasticity was conserved across species. These findings have now defined a high-fidelity platform for achieving iPSC-based biotechnologies (gene editing and cloning) and for exploring different ruminant livestock applications that have not been previously practicable. Of central importance, these findings also open a path to establishing a live regenerative repository of inexhaustible diploid livestock that can secure the evolving genetic needs for sustaining animal production into the future. Permanent assets of genetic diversity preserved as iTPSCs would ensure rapid resilience in production, health and fertility through propagating heterosis and enabling genetic fixes for regional climate-resilient livestock phenotypes that better tolerate environmental extremes. [ABSTRACT FROM AUTHOR]

The ability of a heifer to calve earlier in a breeding season has implications on the economic success of heifers in a production system. Heifers that calve earlier in a calving season have increased calf performance, improved subsequent fertility, and a longer productive life in the herd. Production systems typically breed heifers during fixed breeding dates, with heifers of variable ages in the same contemporary group. The objective of this study was to determine if heifer yearling weight (YW) or age differences going into a fixed breeding period influenced the additive genetic variance of age at first calving (AFC) explained in a multibreed population. Heifer fertility data were obtained from International Genetic Solutions. Females with exposure and calf production records were used to identify individuals calving between 630 and 810 days of age. Females with embryo transfer, multiple birth progeny, and an age differential (DIFF) greater than 100 days were excluded. Age differential was defined as the difference in days between an individual's birth date and the earliest birth date of an animal in a defined contemporary group. Contemporary group was defined as; breeder, herd, year born, birth and yearling group. After data filtering, there were 149,350 calving records. A 3-generation pedigree file was used containing 365,637 animals, with 37,420 unique sires and 219,533 unique dams. Two bivariate multi-trait animal models for AFC and YW with random additive genetic and residual effects and fixed effects of contemporary group, breed proportion, and % retained hybrid vigor were used. The first model consisted of the aforementioned effects while the second model included DIFF as an additional fixed effect. Analyses were performed using ASReml 3.0. When DIFF was not included as a fixed effect, the additive, residual and phenotypic variances for AFC were 126.1, 456.8, and 582.9 d², respectively, and the genetic correlation between AFC and YW was 0.36 ± 0.02. When DIFF was included as a fixed effect, the additive, residual, and phenotypic variances for AFC were 10.0, 326.0, and 336.0 d², respectively. The genetic correlation between AFC and YW was 0.19 ± 0.04. In the absence of DIFF, the heritability estimates for AFC and YW were 0.22 ± 0.01 and 0.44 ± 0.01, respectively but were 0.03 ± 0.003 and 0.44 ± 0.01 respectively, when DIFF was included. Age differential was a significant effect on AFC at -0.86 (P < 0.0001). The low additive variance of AFC when accounting for DIFF suggests that the influence of a female's age going into a fixed breeding date explains much of the variation in AFC. The low heritability estimate for AFC and genetic correlation with YW suggests that selection for improved AFC will be difficult using this method and that producers should instead focus on improved management practices to ensure females calve earlier in a calving season. [ABSTRACT FROM AUTHOR]

Meticulous culling decisions, coupled with careful breeding decisions, are fundamental to shifting a population distribution in the favorable direction and improving profit per cow. Nevertheless, there is a paucity of easy-to-use dynamic tools to aid in culling decisions in beef cattle. The motivation for the present study was to develop a monetary-based culling tool, here referred to as the Beef Female’s Profit Potential (BFPP), to identify females for culling. The BFPP reflects the expected lifetime profitability of an individual female in a herd for the expected remainder of her lifetime; this profit included that of the beef female herself as well as her progeny. The BFPP index framework was composed of 4 subindexes reflecting the value of an animal: (1) as a nulliparae (this was voided if the cow had already calved), (2) for the remainder of her current parity, (3) summed across each of her expected remaining parities, and (4) when she is retained within the herd and not voluntarily culled. Each subindex was comprised of different components reflecting both genetic and non-genetic effects associated with each female. Transition matrices predicting the expected longevity of each female and their expected month of calving were also utilized in calculating the expected remaining lifetime profitability of each female. The BFPP index was validated on 21,102 beef cows as well as their harvested progeny from 875 herds by stratifying the cows, within herd, into 4 strata based on their BFPP. The mean of the within-herd correlation between the BFPP and the Irish national replacement (i.e., breeding) index was, on average, 0.45 indicating the shortcomings of the breeding index as a culling tool. Cows within the top BFPP stratum had a genetic expectation of accruing almost an additional €36 profit per calving, relative to cows within the worst stratum; when validated on the cow’s own calving interval and survival performance as well as their progeny’s carcass performance, the actual phenotypic value was estimated to be an additional €32 profit per calving. A proportion of this additional profit was due to the harvested progeny of the high BFPP cows having, on average, heavier, more conformed carcasses with less fat cover relative to their poor BFPP contemporaries. This BFPP framework is a useful and easy-to-use tool to aid in producer decision making on the choice of females to voluntarily cull but also on which replacement heifers to graduate into the mature herd. [ABSTRACT FROM AUTHOR]

Longevity in commercial sows is often selected for through stayability traits measured in purebred animals. However, this may not be justifiable because longevity and stayability may be subject to both genotype by environment interaction (G × E) and genotype by genotype interaction (G × G). This study tested the hypothesis that stayability to service after first parity is more strongly genetically correlated with longevity in commercial herds when stayability is measured in commercial herds rather than multiplier herds. The analysis was based on farrowing- and service-records from 470,824 sows (189,263 multiplier; 281,561 commercial) and 300 herds (156 multiplier; 144 commercial sows). Multiplier sows were either purebred Landrace or Yorkshire and commercial sows were mainly rotationally crossbreds between the two breeds. Commercial longevity was defined as age in days when culled (LongC), and stayability to service after first parity was defined for both commercial sows (StayC) and multiplier sows (StayM). The genetic correlations between LongC, StayC, and StayM were estimated by restricted maximum likelihood using linear mixed models. Genetic parameters were estimated separately for Landrace and Yorkshire. In Landrace, the genetic correlations between LongC and StayC, LongC and StayM, and StayC and StayM were 0.86 ± 0.02, 0.24 ± 0.05, and 0.34 ± 0.06, respectively. In Yorkshire, the genetic correlations between LongC and StayC, LongC and StayM, and StayC and StayM were 0.81 ± 0.03, 0.17 ± 0.05, and 0.18 ± 0.7, respectively. Conclusively, longevity in commercial herds is more strongly correlated with stayability when stayability is measured in commercial herds rather than multiplier herds. [ABSTRACT FROM AUTHOR]

The objective of the present study was to quantify the genetic and non-genetic contributors to variability in both carcass dressing percentage and dressing difference (i.e. the difference between carcass weight and live weight immediately prior to slaughter) in young animals and cows. The datasets contained 18,479 young animals from 653 herds, and 2,887 cows from 665 herds. Live weight records within 7 d of slaughter and associated carcass weight were available for all animals. Association analyses were undertaken using linear mixed models with fixed effects for the model of young animals consisting of animal breed, days between the date of last recorded live weight and slaughter date, heterosis and recombination loss coefficients, dam parity, a 3-way interaction between whether the animal originated in a dairy or beef herd, animal sex, and age at slaughter, as well as a 2-way interaction between calendar year of slaughter and month of slaughter; contemporary group was included as a random effect. Fixed effects in the cow model were cow breed, the number of days between the date of last recorded live weight and slaughter date, heterosis and recombination loss coefficients, the number of days postcalving, parity of the cow, and a 2-way interaction between calendar year of slaughter and month of slaughter; contemporary group was included as a random effect. The mean dressing percentage (phenotypic standard deviation in parentheses) and dressing difference in young animals were 55.86% (3.21%) and 280.03 kg (41.44 kg), respectively. Steers had the heaviest dressing difference at 34.18 and 60.44 kg heavier than a 16-mo old bull and 22-mo old heifer, respectively. Dressing difference for 30-mo old Simmental steers (breed with heaviest dressing difference) was 41.66 kg heavier than 30-mo old Belgian Blue steers (breed with lightest dressing difference). The heritability of dressing percentage (0.48) and dressing difference (0.35) in young animals was relatively similar to each other, in contrast to dressing percentage (0.08) in cows which was considerably lower than dressing difference (0.28). Considerable genetic variability existed in dressing difference amongst young animals (genetic standard deviation of 15.03 kg), despite the near unity genetic correlation (0.93) between carcass weight and live weight. This therefore indicates that genetic selection for increased saleable product can be achieved by selecting for increased carcass weight while concurrently selecting for lighter animals although the opportunity is limited by the strong part-whole relationships that exists between carcass weight, live weight, and dressing difference. [ABSTRACT FROM AUTHOR]

Understanding fitness level among various breeds is essential for sustainable meat goat production. Research on the relative fitness of Boer F1 does and straightbred base breed has been limited. Meat goat does of various genotypes (Boer, Kiko, Spanish, Boer × Kiko reciprocal F1 crosses, and Boer × Spanish reciprocal F1 crosses) were studied to evaluate breed effects on doe fitness traits and the expression of heterosis over 7 production years. The herd was semi-intensively managed under humid subtropical pasture. Doe age affected (P < 0.05) various traits. Boer × Kiko does were heavier (P < 0.05) than Boer does at fall breeding, but Boer × Spanish does did not differ (P > 0.05) from Boer does for breeding weight. The body weights of Boer × Spanish and Boer × Kiko crosses did not differ (P > 0.05) from the weights of their respective Kiko and Spanish base cohorts at breeding, kidding, or weaning. Boer does had lower (P < 0.05) kidding rate (KR) and weaning rate (WR) than the other breeds and crosses. Boer × Kiko and Kiko were similar for KR and WR. Boer × Spanish and Spanish were also similar for KR and WR. However, the combined group of Boer F1 does had lower (P < 0.01) KR and WR than the combined purebred biotype group of Kiko and Spanish does. Boer does weaned smaller (P < 0.05) litter sizes per doe exposed compared with Kiko, Spanish, Boer × Kiko, and Boer × Spanish does with the latter four doe breedtypes not differing from each other. The combined Boer F1 doe group weaned smaller (P < 0.05) litter sizes per doe exposed than the combined purebred group of Kiko and Spanish does. Boer × Kiko dams had higher (P < 0.05) fecal egg counts at parturition than Kiko dams. Significant heterosis was observed for reproductive traits within each of the 2-breed diallels. Boer F1 does exhibited reproductive output similar to or lower than Kiko and Spanish straightbred does and higher than Boer straightbred does. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of animal trait, breed combination, and climate on the expressed levels of heterosis in crossbreeding schemes using tropical cattle. A meta-analysis of 42 studies was carried out with 518 heterosis estimates. In total, 62.5% of estimates were found to be significantly different from zero, the majority of which (89.8%) were beneficial for the studied trait. Trait and breed combination were shown to have a significant effect on the size of heterosis (P < 0.001 and P = 0.044, respectively). However, climate did not have a significant effect. Health, longevity, and milk production traits showed the highest heterosis (31.84 ± 10.73%, 35.13 ± 14.35%, and 35.15 ± 3.29%, respectively), whereas fertility, growth, and maternal traits showed moderate heterosis (12.02 ± 4.10%, 12.25 ± 2.69%, and 15.69 ± 3.26%, respectively). Crosses between breeds from different types showed moderate to high heterosis ranging from 9.95 ± 4.53% to 19.53 ± 3.62%, whereas crosses between breeds from the same type did not express heterosis that was significantly different from zero. These results show that heterosis has significant and favorable impact on productivity of cattle farming in tropical production systems, particularly in terms of fitness but also milk production traits. [ABSTRACT FROM AUTHOR]

The aim of this study was to estimate the influence of heterosis and breed percentage on calving interval (CI) and gestation length (GL), and the correlation between age at first calving (AFC) and CI, in beef cows. Data included 1,291 repeated observations of CI and GL from 502 cows with 2,840 individuals in the pedigree, including 3 generations from the multibreed herd of the livestock experimental station of the Panama Agricultural Innovation Institute (IDIAP) in Gualaca, Panama. The herd was composed of the following genetic groups based on their breed percentage: tropically adapted Brahman (BR), Nellore (Ne), Undefined Bos indicus (BI), Guaymi Creole (CR), Senepol (SP) and Romosinuano (RS); Bos taurus (BT), Simmental (SM), Angus (A), Red Angus (AR), Limousin (LM), Charolais (CH), Wagyu (Wa), and Others (Oth); crossbreeds (cx), Beefmaster (BF), Three CX (F1 x different BT), R1(Backcross BR), R2 (Backcross BT), Composite (combination of at least 4 different breeds with less than 25% of Zebu), Upgrade (87.5% BR 12.5% BT), B1 (62.5% Zebu + 37.5% BT), and B2 (62.5% BT + 37.5% Zebu). The Zebu influenced breed group represents 50.03% of this population, followed by the F1, the three CX, composites, and R1, representing 22%, 13.89%, 6.11%, and 5.34%, respectively. The other breed groups represented less than 2.5% of the population. A repeated records animal model was used to estimate variance components for both CI and GL. A bivariate animal model was used to estimate the genetic correlation between CI and age at first calving (AFC). Fixed effects for all models consisted of contemporary group, age of dam, calf sex, degree of outcross, and breed percentage. Contemporary group was defined by calving year and season of birth. The average CI was 572.6 ± 140 d, with a range of 315 d to 910 d; and the average GL was 284.2 ± 6.3 d. The estimated regression coefficient for CI on heterosis was -0.114 ± 0.10 d/heterosis % (P = 0.266), and for GL was -0.01 ± 0.052 d/heterosis %. A shorter CI was observed for the F1, and three CX, with 558.7 days and 567.2 days, representing a 2.3% and 1.3% reduction in CI, respectively, when compared with the Zebu group. A larger CI was observed for the Nellore and Romosinuano breeds % with 0.17 ± 1.23 d, (P = 0.373) and 0.64± 0.13 d (P = 0.406), respectively. A low heritability (0.037 ± 0.026) for CI was estimated, with a positive genetic trend over the duration of the study. The analysis between CI and AFC revealed a moderate genetic correlation (0.49 ± 0.36) that allows the establishment of a selection program to improve AFC and CI, which would improve the fertility of this multi-breed herd in Panama. [ABSTRACT FROM AUTHOR]

Nellore-Angus steers (n = 572) born in 2009-2013, 2015, and 2019 and Brahman-Angus reciprocal steers (n = 73) born in 2019 and 2020 were evaluated for calf and carcass weights (HCW). Calves were born and reared at the McGregor Research Center and included F2, F3, F4, and F5 Nellore-Angus and F1 Brahman-Angus. Calves were weighed at 4 approximate times: within 48 h of birth (BWT), 50 d age (springworking, SWWT, not available for 2009-2010), 180 d age (pre-weaning, PRWWT), and approximately 210 d age (weaning, WWT). Animals born in the same year were managed similarly, and cow herds were managed together in most cases except during annual natural service, multi-sire breeding seasons. Animals born in the same year were managed as contemporaries postweaning and for feedlot finishing. Mixed model analyses of variance for calf traits included genetic type (nested within calf birth year), calf birth year, age of dam category, and covariates of Julian birth date (BWT, SWWT) or calf age (PRWWT and WWT) as fixed effects. In each year at least 2 genetic types were present; however, because of imbalance across years, only genetic types produced in the same years were compared following significant F-tests. For these analyses cow age category did not affect calf BWT or SWWT, but showed influence for PRWWT (P = 0.006) and WWT (P < 0.001); cow age category did not affect calf ADG. Differences in calf weights (P < 0.001) and calf ADG (P < 0.001) due to the genetic type were driven by reciprocal differences between Brahman-Angus crosses and potential maternal hybrid vigor advantages for F2 Nellore-Angus calves from F1 dams vs. other genetic types. Brahman-sired F1 (B × A) males were 12.7 to 14.1 kg heavier for BWT (P < 0.001) and 14.9 to 19.2 kg heavier for SWWT (P < 0.001) than Angussired F1 males (A × B), but persistence to weaning varied across years. It appears in these data that some genetic types may be more sensitive to individual year effects, but it is uncertain why. Correlations of calf weight traits with HCW were inconsistent across genetic types. No calf weight was associated with HCW in A × B crosses, and only PRWWT in B × A related to HCW (r = 0.44, P = 0.007). Among Nellore-Angus crosses, BWT showed small to moderate correlation to HCW (0.23 < r < 0.46); however, among the F4 and F5 calves, later weights (SSWT, PRWWT and WWT) had large correlations with HCW (0.50 < r < 0.79) whereas these correlations ranged from 0.24 to 0.37 in F2 and F3 steers. It appears animals of similar Bos indicus percentage may have quite different calf growth patterns related to HCW. [ABSTRACT FROM AUTHOR]

In standard laboratory conditions, inbred mouse strains with normal kidney function show a 4-fold range of daily water consumption. This study uses two strains of inbred mice identified as high and low consumers, their reciprocal F1 crosses, and inter se bred F2s. Daily consumption data were collected on 607 animals for 4 d during the 4th, 5th, and 6th wk using custom water bottles. Animals were weighed at the beginning of the 4th, 5th, 6th, and 7th wk. Consumption data were corrected for metabolic BW (Bwt0.67) prior to analysis, so units of water consumption are expressed in mL consumed per gram of Bwt0.67 per day. Variables BW and water consumption were fitted to a mixed model including the effects of sex, strain, and their interaction with sire within strain fitted as a random effect. Contrasts were designed to test the direct genetic, maternal genetic, individual heterosis, and maternal heterosis effects. An interaction (P < 0.0001) was observed between sex and strain so all analyses were conducted separately for each sex. C57Brown/CDJ animals (Brown) consumed more water than C57Black/10J animals (Black) (P < 0.0001). A maternal effect (P = 0.036, P = 0.029) was observed in males at the 4th and 5th wk as F1 animals with a Black dam (F1Black) consumed less than F1 animals with a Brown dam (F1Brown) males. No significant heterosis effect was observed for water consumption. For weight analysis, Black animals were significantly larger than Brown animals at 28 d (males P = 0.004, females P = 0.026), but no difference was observed the remainder of the trial. Further, F1Brown females were significantly smaller than F1Black females at 28 d (P < 0.0001) and F1Brown males tended to be smaller than F1Black males (P = 0.078). Animals from the reciprocal F1 crosses showed an increase in birth weight (P < 0.0001) over pure strains. These strains form the foundation stock of an experiment designed to isolate genes influencing water consumption by reciprocal backcrossing and selection. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare growth from birth to slaughter of different breed groups that were raised in Rio Grande do Sul, Brazil and estimate the consequent breed additive and heterosis effects. Caracu (C), Hereford (H), and Nelore (N) sires were mated with Angus (A) dams, and A sires were mated with H and N dams to produce a first generation of crossbred progeny that was contemporary with purebred A, H, and N calves. Heifers from this first generation (G1) were mated with Brangus (BN) and Braford (BO) sires to produce a second generation (G2) of progeny. Data were analyzed to estimate breed group means, individual and maternal breed additive effects, and heterosis effects on birth weight, weaning weight, preweaning average daily gain, yearling weight, postweaning average daily gain, fattening phase initial weight (around 19 mo), final weight (around 24 mo), average daily gain in the fattening phase, and age at slaughter. In general, crossbred calves outperformed purebred calves. Angus-N and CA crossbred cows weaned heavier calves. Individual taurine-indicine heterosis (Z) significantly increased weaning weight. The AN, NA, and CA steers were heaviest at yearling, whereas NA, CA, AN, and HA had the greatest final weights. However, AH steers were 1 mo older at slaughter than NA contemporaries. Taurine breed effects on postweaning traits and final weight were greater than for N. Maternal breed effects on birth weight and average daily gain in the fattening phase were greater for A and H than for N. In conclusion, heterosis effects were sufficiently large for use of N to be recommended as a component of such systems, despite their relatively low-breed additive effects compared with taurine breeds. Moreover, germplasm from the tropically adapted Bos taurus C may be particularly useful when increased milk production is desired. With the breed and heterosis effects derived in the present study, it is possible to predict the performance and infer which breed and breed crosses will perform better in crossbreeding systems designed for the subtropical conditions of southern Brazil and similar regions. [ABSTRACT FROM AUTHOR]

Ewe efficiency has traditionally been defined as the ratio of litter weight to ewe weight; given the statistical properties of ratio traits, an alternative strategy is proposed in the present study. The concept of using the deviation in performance of an animal from the population norm has grown in popularity as a measure of animal-level efficiency. The objective of the present study was to define novel measures of efficiency for sheep, which considers the combined weight of a litter of lambs relative to the weight of their dam, and vice versa. Two novel traits, representing the deviation in total litter weight at 40 d (DEV40L) or weaning (DEVweanL), were calculated as the residuals of a statistical model, with litter weight as the dependent variable and with the fixed effects of litter rearing size, contemporary group, and ewe weight. The deviation in ewe weight at 40-d postlambing (DEV40E) or weaning (DEVweanE) was derived using a similar approach but with ewe weight and litter weight interchanged as the dependent variable. Variance components for each trait were estimated by first deriving the litter or ewe weight deviation phenotype and subsequently estimating the variance components. The phenotypic SD in DEV40L and DEVweanL was 8.46 and 15.37 kg, respectively; the mean litter weight at 40 d and weaning was 30.97 and 47.68 kg, respectively. The genetic SD and heritability for DEV40L was 2.65 kg and 0.12, respectively. For DEVweanL, the genetic SD and heritability was 4.94 kg and 0.13, respectively. The average ewe weight at 40-d postlambing and at weaning was 66.43 and 66.87 kg, respectively. The genetic SD and heritability for DEV40E was 4.33 kg and 0.24, respectively. The heritability estimated for DEVweanE was 0.31. The traits derived in the present study may be useful not only for phenotypic benchmarking of ewes within flock on performance but also for benchmarking flocks against each other; furthermore, the extent of genetic variability in all traits, coupled with the fact that the data required to generate these novel phenotypes are usually readily available, signals huge potential within sheep breeding programs. [ABSTRACT FROM AUTHOR]

An objective of commercial beef cattle crossbreeding programs is to simultaneously optimize use of additive (breed differences) and non-additive (heterosis) effects. A total of 6,794 multibreed and crossbred beef cattle with phenotype and Illumina BovineSNP50 genotype data were used to predict genomic heterosis for growth and carcass traits by applying two methods assumed to be linearly proportional to heterosis. The methods were as follows: 1) retained heterozygosity predicted from genomic breed fractions (HET1) and 2) deviation of adjusted crossbred phenotype from midparent value (HET2). Comparison of methods was based on prediction accuracy from cross-validation. Here, a mutually exclusive random sampling of all crossbred animals (n = 5,327) was performed to form five groups replicated five times with approximately 1,065 animals per group. In each run within a replicate, one group was assigned as a validation set, while the remaining four groups were combined to form the reference set. The phenotype of the animals in the validation set was assumed to be unknown; thus, it resulted in every animal having heterosis values that were predicted without using its own phenotype, allowing their adjusted phenotype to be used for validation. The same approach was used to test the impact of predicted heterosis on accuracy of genomic breeding values (GBV). The results showed positive heterotic effects for growth traits but not for carcass traits that reflect the importance of heterosis for growth traits in beef cattle. Heterosis predicted by HET1 method resulted in less variable estimates that were mostly within the range of estimates generated by HET2. Prediction accuracy was greater for HET2 (0.37-0.98) than HET1 (0.34-0.43). Proper consideration of heterosis in genomic evaluation models has debatable effects on accuracy of EBV predictions. However, opportunity exists for predicting heterosis, improving accuracy of genomic selection, and consequently optimizing crossbreeding programs in beef cattle. [ABSTRACT FROM AUTHOR]

The Spooner Agricultural Research Station operated the only dairy sheep research flock in North America through 2016. The original nondairy ewe flock was "bred up" to a crossbred dairy flock through the use of rams and semen of the East Friesian (EF) and Lacaune (LA) dairy breeds. The objective of this study was to determine the environmental and nonadditive genetic effects that influence performance of dairy ewes. The traits analyzed were 180 d adjusted milk (180d MY), fat (180d FY), and protein (180d PY) yields, percentage fat (%F) and protein (%P) in milk, lactation average somatic cell score (LSCS), and number of lambs born per ewe lambing (NLB). The univariate repeatability models included the fixed effects of year of lambing, age, weaning system (except for the trait of NLB), individual breed composition, and individual retained heterosis along with the random additive genetic, permanent environmental, and residual effects. Estimates of heritability were moderate for 180d MY (0.32 ± 0.04), 180d FY (0.26 ± 0.04), and 180d PY (0.29 ± 0.04), high for %F (0.54 ± 0.04) and %P (0.61 ± 0.04), and low for LSCS (0.12 ± 0.03) and NLB (0.08 ± 0.02). Ewes that reared their lambs had lower (P < 0.01) 180d MY, 180d FY, 180d PY, %F, and %P and higher (P < 0.001) LSCS than ewes that had their lambs removed shortly after parturition. Relative to nondairy breeding, EF and LA breeding had positive (P < 0.001) effects on 180d MY, 180d FY, and 180d PY, but a negative (P < 0.03) effect on %P. Purebred EF ewes were predicted to have lower (P < 0.001) %F than purebred LA or nondairy ewes. Purebred LA ewes were predicted to have a higher (P < 0.001) LSCS than purebred EF or nondairy ewes. Purebred EF ewes were expected to be more (P < 0.001) prolific than purebred LA or nondairy ewes. Individual retained heterosis had a favorable (P < 0.01) effect on 180d MY, 180d FY, 180d PY, and NLB. Knowledge of the factors affecting dairy ewe performance are important for dairy sheep producers to make more informed husbandry and breeding decisions. [ABSTRACT FROM AUTHOR]

The study assesses the need for and effectiveness of using ridge regression when estimating regression coefficients of covariates representing genetic effects due to breed proportion in a crossbreed genetic evaluation. It also compares 2 ways of selecting the ridge parameters. A large crossbred Angus ? Nellore population with 294,045 records for weaning gain and 148,443 records for postweaning gain was used. Phenotypic visual scores varying from 1 to 5 for weaning and postweaning conformation, weaning and postweaning precocity, weaning and postweaning muscling, and scrotal circumference were analyzed. Three models were used to assess the need for ridge regression, having 4, 6, and 8 genetic covariates. All 3 models included the fixed contemporary group effect and random animal, maternal, and permanent environment effects. Model AH included fixed direct and maternal breed additive and the direct and maternal heterosis covariates, model AHE also included direct and maternal epistatic loss covariates, and model AHEC further included direct and maternal complementarity effects. The normal approach is to include these covariates as fixed effects in the model. However, being all derived from breed proportions, they are highly collinear and, consequently, may be poorly estimated. Ridge regression has been proposed as a method of reducing the collinearity. We found that collinearity was not a problem for models AH and AHE. We found a high variance inflation factor, >20, associated with some maternal covariates in the AHEC model reflecting instability of the regression coefficients and that this instability was well addressed by using ridge regression using a ridge parameter calculated from the variance inflation factor. [ABSTRACT FROM AUTHOR]

The use of Brahman in cow-calf production offers some adaptation to the harsh characteristics of endophyte-infected tall fescue. Criollo breeds, such as the Romosinuano, may have similar adaptation. The objectives were to estimate genetic effects in Romosinuano, Angus, and crossbred cows for their weights, weights of their calves, and ratios (calf weight:cow weight and cow weight change:calf weight gain) across lactation and to assess the influence of forage on traits and estimates. Cows (n = 91) were bred to Charolais bulls after their second parity. Calves (n = 214) were born from 2006 to 2009. Cows and calves were weighed in early (April and June), mid- (July), and late lactation (August and October). Animal was a random effect in analyses of calf data; sire was random in analyses of cow records and ratios. Fixed effects investigated included calf age, calf sex, cow age-year combinations, sire breed of cow, dam breed of cow, and interactions. Subsequent analyses evaluated the effect of forage grazed: endophyte-free or endophyte-infected tall fescue. Estimates of maternal heterosis for calf weight ranged from 9.3 ± 4.3 to 15.4 ± 5.7 kg from mid-lactation through weaning (P < 0.05). Romosinuano direct effects (of the cow) were -6.8 ± 3.0 and -8.9 ± 4.2 kg for weights recorded in April and June. Calf weights and weight gains from birth were greater (P < 0.05) for calves of cows grazing endophyte-free tall fescue except in mid-summer. Cow weight change from April to each time was negative for Angus cows and lower (P < 0.05) than other groups. Cows grazing endophyte-free tall fescue were heavier (P < 0.05) at all times but had more weight loss in late lactation. Angus cows had the lowest (P < 0.05) ratios (negative) of cow weight change:calf weight gain, indicating an energy-deficit condition. Cows grazing endophyte-free tall fescue had more negative (P < 0.05) values for this trait but not in early lactation (P < 0.05). Estimates of heterosis ranged from 12.8 ± 9.5 to 28.6 ± 9.4 kg for cow weight, 7.9 ± 3.0 to 15.8 ± 5.0 kg for cow weight change, and 0.07 ± 0.03 to 0.27 ± 0.1 for cow weight change:calf weight gain. Direct Romosinuano effects ranged from 14.8 ± 4.2 to 49.8 ± 7.7 kg for cow weight change and 0.2 ± 0.04 to 0.51 ± 0.14 for cow weight change:calf weight gain. The adaptive ability of Romosinuano in temperate fescue regions may be favorable with respect to relative cow and calf weight but may be a consequence of lower milk-producing ability. [ABSTRACT FROM AUTHOR]

The aim of this study was to estimate the influence of heterosis and breed percentage on birth weight (BW) and weaning weight (WW) in beef cows in a tropical environment. Data from 900 calves and 2,843 individuals in the pedigree, from the multibreed herd of the Panama Agricultural Innovation Institute (IDIAP) in Gualaca, Panama were used. The herd was comprised of the following genetic groups and according to their breed percentage: tropical adapted Brahman (BR), Nellore (Ne), Un define Bos indicus (BI), Guaymi Creole (CR), Senepol (SP) Romosinuano (RS); Bos taurus (BT), Simmental (SM), Angus (A), Red Angus (AR), Limousin (LM), Charolais (CH), Wagyu (Wa), and Others (Oth); crossbreeds (cx), Beefmaster (BF), Three cx(F1 x different BT), R1(Backcross BR), R2 (Backcross BT), Composite (combination of at least 4 different breeds with less than 25% of Zebu), Upgrade (87.5% BR 12.5% BT), B1 (62.5% Zebu + 37.5% BT), B2 (62.5% BT + 37.5% Zebu). A bivariate animal model for BW and WW, was utilized to estimate variance components. Contemporary group was defined as year of birth. The effects of sex, birth season, weaning season, and age of dam were included as categorical fixed effects. Weaning age, degree of outcross and breed percentage were included as linear covariates. The estimated regression coefficient for BW on heterosis was not significant (P > 0.05), and for WW was 0.072 ± 0.027 kg (P < 0.05). Lower BW and WW were observed for the Japanese, and B1, while R2 and Upgrade had the highest average (P < 0.05). Heritability for BW was found to be low (0.14 ± 0.06) and moderate for WW (0.26 ± 0.09). The proportion of variation of WW accounted by maternal permanent environment for WW was (0.2 ± 0.09). The estimated genetic correlation between additive genetic BW and WW was 0.63 ± 0.30, while a negative, additive genetic correlation was observed for WW and WW maternal (-0.43 ± 0.37). These results suggested that heterosis had a beneficial influence on WW but limited effect on BW. Additionally, increasing the percentage of Wa, and BR negatively influenced WW measurements in a multibreed beef cattle herd in Panama. [ABSTRACT FROM AUTHOR]

Heterosis is the tendency of crossbreed animals performing better than the average of the purebred parents. Heterosis retention is essential in crossbreeding and composite breeding systems. However, not every genomic region benefits from heterosis, with certain traits showing an improvement when certain genomic regions are kept fixed for a certain breed. The objectives of this study were to detect such regions in a commercial Brangus herd, using genotypes, and Breed of Origin (BO) genotypes to identify runs of homozygosity (ROH) and investigate their effects on meat traits. The Brangus herd was genotyped with the Bovine GGP F250 array, after quality control, 99,669 variants, and 1,046 cattle remained. These genotypes were converted into BO genotypes with LAMP-LD, which describes the origin of the markers either from Angus or Brahman ancestry. The new BO genotypes and original genotypes were then used to identify ROH using the -homozyg function PLINK. The ROH genotypes were fit into a single locus mixed model for hot carcass weight (HCW) and marbling (MARB) using the EMMAX procedures in Golden Helix. The same single locus mixed model was used on both genotypes and Breed of Origin genotypes using the EMMAX procedures in Golden Helix. Using BO alleles, and ROH alongside traditional genotypes can help identify regions with significant effects on carcass traits. Providing important information for crossbreeding/composite breed systems about regions which should remain fixed for breeds. [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate genetic and nongenetic effects affecting survival in crossbred lambs during 3 time periods: through 1 d of age (n = 7,933), 2 to 30 d of age (n = 5,370), and 2 to 60 d of age (n = 5,216) in a population being upgraded to the dairy breeds of East Friesian and Lacaune in which lambs were artificially reared on milk replacer. Survival was analyzed for lambs born in 14 yr from 1998 to 2011 using pedigree information from 14,339 animals born in 23 yr from 1989 to 2011. Date of death, sex, age of the dam, birth type, month and year of birth, and breed composition were recorded, and the proportion of retained heterosis was calculated for each animal. Lambs were crossbreds of 2 or more breeds with 14 breeds represented in the population. Due to low mean genetic contribution of the 12 nondairy breeds, they were placed into 2 groups: meat breeds (Hampshire, Suffolk, and Texel) and maternal breeds (Romanov, Finnsheep, Dorset, Targhee, Rambouillet, Polypay, Katahdin, Arcott Rideau, and Commercial). The proportion of individual retained heterosis was positively associated (P < 0.05) with lamb survival from 2 to 30 and from 2 to 60 d of age. The predicted increase in survival of F1 lambs compared to purebred lambs was +8.8 and +14.6%, respectively. Predicted survival of meat breed lambs and maternal breed lambs was greater (P ≤ 0.01) than Lacaune lambs during all 3 periods. Predicted survival of East Friesian lambs was consistently lower (P ≤ 0.01) than meat breed and maternal breed lambs during all periods. The predicted survival of East Friesian lambs was numerically greater but not significantly different from Lacaune lambs. There was a lower (P < 0.01) survival of females compared to males through 1 d of age (-5.6%), but females had higher (P < 0.01) survival than males in the other 2 periods (2 to 30 d = +3.3% and 2 to 60 d = +6.0%). Through 1 d of age, lambs of triplet and greater birth types had lower (P < 0.01) survival than single lambs (-6.2%), and lambs from 1-yr-old dams had lower (P < 0.01) survival than lambs from 2-yr-old dams (+4.5%). Estimates of heritability of lamb survival were 0.14 (SE = 0.03), 0.03 (SE = 0.04), and 0.06 (SE = 0.03) for the 3 time periods, respectively. An increase in the proportion of individual retained heterosis was the most important genetic factor associated with increased lamb survival in this study. [ABSTRACT FROM AUTHOR]

Heterosis, assumed proportional to expected breed heterozygosity, was calculated for 6834 individuals with birth, weaning and yearling weight records from Cycle VII and advanced generations of the U.S. Meat Animal Research Center (USMARC) Germplasm Evaluation (GPE) project. Breeds represented in these data included: Angus, Hereford, Red Angus, Charolais, Gelbvieh, Simmental, Limousin and Composite MARC III. Heterosis was further estimated by proportions of British × British (B × B), British × Continental (B × C) and Continental × Continental (C × C) crosses and by breed-specific combinations. Model 1 fitted fixed covariates for heterosis within biological types while Model 2 fitted random breed-specific combinations nested within the fixed biological type covariates. Direct heritability estimates (SE) for birth, weaning,and yearling weight for Model 1 were 0.42 (0.04), 0.22 (0.03), and 0.39 (0.05), respectively. The direct heritability estimates (SE) of birth, weaning, and yearling weight for Model 2 were the same as Model 1, except yearling weight heritability was 0.38 (0.05). The B × B, B × C, and C × C heterosis estimates for birth weight were 0.47 (0.37), 0.75 (0.32), and 0.73 (0.54) kg, respectively. The B × B, B × C, and C × C heterosis estimates for weaning weight were 6.43 (1.80), 8.65 (1.54), and 5.86 (2.57) kg, respectively. Yearling weight estimates for B × B, B × C, and C × C heterosis were 17.59(3.06), 13.88 (2.63), and 9.12 (4.34) kg, respectively. Differences did exist among estimates of breed-specific heterosis for weaning and yearling weight, although the variance component associated with breed-specific heterosis was not significant. These results illustrate that there are differences in breed-specific heterosis and exploiting these differences can lead to varying levels of heterosis among mating plans. [ABSTRACT FROM AUTHOR]

Crosses between different mink lines from 3 Danish mink farms that use different breeding strategies were studied to estimate heterosis and variance components for litter size. The study was designed to analyze crosses between lines of the same color type, between different color types, and between animals originating from different farms. Effect of heterosis, color type, and variance components were estimated using Average information REML (AI-REML) algorithm implemented in the DMU package for analyzing multivariate mixed models. Females from 7 generations that gave birth to at least 1 offspring were analyzed and the effects of parity and production year were included in the analyses. Genetic trend and the proportions of the total variance explained by the effects of additive genetics (h2), common environment (due to repeated litters from the same female; c2), and dam of the female (granddame of the bom litter; d2) were estimated. The results showed that mink of the Black color type potentially produced smaller litters compared to mink of the other studied color types. We found significant general maternal effect of heterosis for litter size. Analyses of specific heterosis showed a significant positive effect of crossing between lines of the same color type. Estimates of variance components revealed h2 levels for farm A, B, and C of 0.15, 0.06, and 0.09, respectively; thus litter size could be selected for in the future. The effect of common environment on litter size was also considerable, with c2 values of 0.005, 0.11, and 0.15 at farms A, B, and C, respectively. In conclusion, we recommend genetic selection as a means of increasing litter size in farmed mink. [ABSTRACT FROM AUTHOR]

A crossbreeding experiment between 4 Spanish maternal lines of rabbits was performed to estimate crossbreeding effects on litter size components. The experiment was designed as a complete diallel cross involving 4 lines selected for litter size at weaning (A, V, H, and LP [L]) and their 12 simple crosses. Does from these 16 genetic groups were distributed among 4 Spanish farms, but only V line was present in all farms, allowing connectivity of the data. A total of 2,015 does in the third, fourth, or fifth gestations were subjected to laparoscopy. The recorded traits were ovulation rate (OR), number of implanted embryos (IE), total born (TB), embryo survival (ES), foetal survival (FS), and prenatal survival (PS). The differences in direct genetic effects, maternal genetic effects, and individual heterosis between the lines were estimated according to Dickerson' s model. Line A was significantly inferior to lines V and H, whereas line LP was similar to A line, but for FS and PS, line A showed the best values, followed by line LP. Comparing crossbred groups to line V, significant differences were shown favoring crossbred groups for OR and IE. The crossbred groups presented high implantation rate, but the foetal survival was lower than in V line. Important values for commercial production were presented by some crosses for OR (HV, 1.26 ova), IE (AH, 1.50 embryos; HV, 1.41 embryos), and TB (AH, 0.82 rabbits; HV, 0.78 rabbits). Relevant and significant reciprocal effects were found, especially for OR in all cases except the LV and VL crosses. These differences become nonsignificant in most of the other traits. Regarding direct genetic effects, line A presented lower estimates than the other lines with important values for OR, but the opposite was observed for FS. The maternal effects were significant only for some contrasts in OR and revealed that the LP line was inferior to the others (1.08 ova compared to the A line, 1.23 compared to the H line, and 0.38 compared to the V line). In general, high positive values for heterosis were found in crossbred does for OR and IE. The crosses, where lines A and H were involved, showed significant heterosis. The highest values were obtained by crossing lines A and H (1.18 ova for OR, 1.87 embryos for IE) followed by the cross between lines H and V. Crosses between line LP and the other lines had a negative heterosis for FS and PS. [ABSTRACT FROM AUTHOR]

The objectives of this work were to compare the Criollo breed Romosinuano as straightbred and crossbred cows with Angus and Brahman in subtropical Florida and to estimate heterosis for size traits of their calves, their own weight, and maternal efficiency traits. Cows (n = 404) were born from 2002 to 2005. After their first exposure to bulls as young cows, crossbred cows were bred to bulls of the third breed, and straightbred cows were bred in to bulls of the other 2 breeds. Calves were spring-born from 2005 through 2011. Evaluated calf (n = 1,254) traits included birth weight and weight, ADG, BCS, and hip height at weaning. Cow weight (n = 1,389) was recorded at weaning. Maternal efficiency traits evaluated included weaning weight per 100 kg cow weight, weaning weight per calving interval, and weaning weight per cow exposed to breeding (n = 1,442). Fixed effects and their interactions were investigated included sire and dam breed of cow, sire breed of calf, cow age, year, calf gender, and weaning age as a linear covariate (calf traits at weaning). Direct and maternal additive genetic effects were random in models for calf traits; only direct additive effects were modeled for cow traits. Cows sired by Angus bulls from outside the research herd had calves that were heavier at birth and weaning and greater ADG, BCS, and hip height (P < 0.05). Estimates of heterosis for weaning weight, BCS, and ADG ranged from 1.3 to 13.2% for all pairs of breeds (P < 0.05). Estimates of heterosis for birth weight (3.2 to 8.2%) and hip height (2.3%) were significant for Romosinuano-Angus and Brahman-Angus. Heterosis for cow weight was 65 ± 8 kg for Brahman-Angus (P < 0.001), and estimates for other pairs of breeds were approximately one-half that value. Heterosis for weaning weight/100 kg cow weight was 3.4 ± 0.75 kg for Romosinuano-Angus. Heterosis estimates for weaning weight/calving interval (P < 0.001) ranged from 0.08 ± 0.01 to 0.12 ± 0.01. Heterosis for weaning weight/cow exposed were 31.6 7.7, 36.9 ± 7.4, and 59.1 ± 7.5 kg for Romosinuano-Angus, Romosinuano-Brahman, and Brahman-Angus, respectively (P < 0.001). Most aspects of Romosinuano crossbred maternal performance were acceptable; maternal performance of Brahman-Angus cows excelled. [ABSTRACT FROM AUTHOR]

The objectives of this work were to compare reproduction and parturition traits of the Criollo breed Romosinuano as straightbred and crossbred cows with Angus and Brahman, to estimate heterosis and direct and maternal genetic breed effects, and to describe calf loss, cow removals from the project, the occurrence of calving difficulty, inadequate calf vigor at birth, and udder problems by cow breed groups. Cows (n = 404) were bom from 2002 to 2005. After their first exposure to bulls as young cows, in all subsequent breeding seasons crossbred cows were bred to bulls of the third breed, and straightbred cows were bred to bulls of the other two breeds. Calving records (n = 1,484) from 2005 to 2011 were used to create calving and weaning rate and calving interval (excluding the interval between 2 and 3 yr of age). Final models for these traits included sire breed-dam breed interaction, cow age within year, and random animal effects. Heterosis estimates for Romosinuano-Brahman calving and weaning rate were 0.06 ± 0.02 and 0.07 ± 0.03 (P < 0.05); those for Brahman-Angus were twice as large (0.13 ± 0.03 and 0.14 ± 0.03, respectively; P < 0.001). Estimates of Brahman direct effects on calving and weaning rate were -0.12 ± 0.04 and -0.14 ± 0.05 (P < 0.05); however, Angus direct effects were beneficial for both traits (0.1 ± 0.05, P < 0.05). The effect of heterosis was to reduce calving interval by -49.2 ± 9.9 and -37.2 ± 9.7 d for Romosinuano-Brahman and Brahman-Angus, respectively (P < 0.001). Romosinuano and Fj cows sired by Romosinuano and out of Angus dams had the most occurrences of difficult births as a proportion of cows that calved (0.028 and 0.025, P = 0.04). Angus-sired crossbred cows and Brahman cows had the most occurrences of udder problems as a proportion of lac-tating cows (0.14 to 0.21, P < 0.04). There were more Brahman-sired cows that died or were culled as a proportion of those cows that began the project (0.1 to 0.28, P < 0.02) than cows in the other breed groups. Romosinuano-Brahman and Romosinuano-Angus cow performance was acceptable, but for most traits, those pairs of breeds had lower heterosis than Brahman-Angus. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate maternal breed effects, direct breed effects, and individ-ual heterosis on subsequent steer performance, carcass, and feed efficiency traits. This was a consecutive 2-yr trial using 158 steers. The same dam breeds, Angus (AN) and purebred Simmental (SM), were used both years. Also, the same AN and SM sires («=11) were used both years. Steers were AN, SM, or AN x SM breed com-position. Steers were managed similarly before wean-ing and early weaned at 56 ± 9 d of age. Steers were then randomly allotted to pens and fed a common fin-ishing ration. Contrasts were written to evaluate direct and maternal breed effects and individual heterosis in the PROC MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) using dam breed, sire breed, and year as fixed effects. Simmental direct breed effect resulted in a 26 kg heavier initial BW {P < 0.05) and a 46 kg heavier final BW (P < 0.05). Simmental maternal breed effect increased initial BW by 43.5 kg (P < 0.05). Dry matter intake was not impacted by direct breed effects, mater-nal breed effects, or individual heterosis. Individual het-erosis did improve G:F 3.4% (P < 0.05) and residual BW gain 0.048 kg/d (P < 0.05). Residual intake and BW gain tended (P = 0.07) to improve as a result of individu-al heterosis. Residual feed intake (RFI) was impacted by direct breed effect with SM cattle having a more desir-able RFI (P = 0.05). Angus direct breed effect increased backfat (P < 0.05) and improved marbling score by 126 units (P< 0.05). Simmental direct breed effect increased LM area {P < 0.05), had the highest HCW at 410 kg (P < 0.05), and had the most desirable yield grade at 2.74 (P < 0.05). Individual heterosis improved marbling score (P = 0.05). Maternal breed effect increased HCW (P < 0.05) as a result of the SM dam. Direct breed effects were present for performance, feed efficiency measures, and carcass traits. Overall, heterosis impacted feedlot performance, carcass characteristics, and feed efficien-cy, which impacts beef production. [ABSTRACT FROM AUTHOR]

Crossbreeding is a common practice among commercial sheep producers to improve animal performance. However, genetic evaluation of U.S. sheep is performed within breed type (terminal sire, semi-prolific, and western range). While incorporating crossbred records may improve assessment of purebreds, it requires accounting for heterotic and breed effects in the evaluation. The objectives of this study were to: 1) describe the development of a paternal composite (PC) line, 2) determine the effect of direct and maternal heterosis on growth traits of crossbred lambs, 3) estimate (co)variance components for direct and maternal additive, and uncorrelated maternal environmental, effects, and 4) provide an interpretation of the estimates of random effects of genetic groups, and to use those solutions to compare the genetic merit of founding breed subpopulations. Data included purebred and crossbred records on birth weight (BN; n = 14,536), pre-weaning weight measured at 39 or 84 d (WN; n = 9,362) depending on year, weaning weight measured at 123 d (WW; n = 9,297), and post-weaning weight measured at 252 d (PW; n = 1,614). Mean (SD) body weights were 5.3 (1.1), 16.8 (3.9) and 28.0 (7.6), 39.1 (7.2), and 54.2 (8.7) kg for BN, WN (at the two ages), WW, and PW, respectively. In designed experiments, the Siremax, Suffolk, Texel, Polypay, Columbia, Rambouillet, and Targhee breeds were compared within the same environment. Estimates of heterotic effects and covariance components were obtained using a multiple trait animal model. Genetic effects based on founders' breeds were significant and included in the model. Percent estimates of direct heterosis were 2.89 ± 0.61, 2.60 ± 0.65, 4.24 ± 0.56, and 6.09 ± 0.86, and estimates of maternal heterosis were 1.92 ± 0.87, 4.64 ± 0.80, 3.95 ± 0.66, and 4.04 ± 0.91, for BN, WN, WW, and PW, respectively. Correspondingly, direct heritability estimates were 0.17 ± 0.02, 0.13 ± 0.02, 0.17 ± 0.02, and 0.46 ± 0.04 for BN, WN, WW, and PW. Additive maternal effects accounted for trivial variation in PW. For BN, WN, and WW, respectively, maternal heritability estimates were 0.16 ± 0.02, 0.10 ± 0.02, and 0.07 ± 0.01. Uncorrelated maternal environmental effects accounted for little variation in any trait. Direct and maternal heterosis had considerable impact on growth traits, emphasizing the value of crossbreeding and the need to account for heterosis, in addition to breed effects, if crossbred lamb information is included in genetic evaluation., (Published by Oxford University Press on behalf of the American Society of Animal Science 2022.)

The article focuses on a study to determine heterosis and breed genetic effects for carcass quantity, quality and palatability traits of steers produced from striaghtbred and crossbred of Romosinuano, Brahman and Angus bulls and cows. It informs that Romosinuano steers had some quality and palatability advantage relative to Brahman but did not provide a clear superior alternative to Brahman for U.S. producers. It discusses the results which states that Romosinuano-Angus estimates was smallest.

Bucklings (n = 275) from a complete diallel of Boer, Kiko, and Spanish meat goats were slaughtered at 7 mo of age (4 mo postweaning) to evaluate genetic effects on carcass yield. Breed of sire did not affect (P > 0.05) live, carcass, and primal weights. Conversely, breed of dam was a consistently significant source of variation for carcass weight traits. Kiko dams produced kids with heavier (P < 0.05) live, carcass, and primal weights than Boer dams. Weights from Spanish dams were intermediate to Boer and Kiko with the significance of differences varying by trait. Cold carcass dressing percent was affected (P < 0.01) by breeds of sire and dam. Boer sires decreased (P < 0.05) dressing percent compared with Kiko and Spanish sires. Dressing percent was also less (P < 0.01) from Boer dams than from Kiko dams; Spanish dams were intermediate and did not differ (P > 0.05) from Boer or Kiko. Subjective conformation scores for muscularity were affected (P < 0.01) by breeds of sire and dam. Boer-sired kids had better (P < 0.01) live scores than Kiko-sired kids. Progeny of Boer dams had better (P < 0.05) live scores than progeny of Spanish dams. Boer-sired kids also had better carcass scores (P < 0.05) than Kiko-sired and Spanish-sired kids. Breed differences for primal cut proportions were negligible. Proportional boneless meat yields did not vary (P > 0.05) by breeds of sire or dam. Direct effects of Boer were negative for carcass weight, dressing percent, and shoulder weight and positive for proportional leg weight. Direct effects of Kiko were positive for carcass weight and shoulder weight and negative for proportional leg weight. Direct effects of Spanish did not differ (P > 0.10) from 0 for any trait tested. Heterosis levels were similar among breed pairings. Heterosis was substantial (P ⩽ 0.05) for live, carcass, and primal weights (5 to 9%) but not for dressing percent, proportional boneless meat yield, or primal weight proportions (<2%). Significant genetic variation was observed among goat breeds for carcass yield traits. Dam breed was more influential than sire breed. Boer germplasm was not superior to Kiko or Spanish germplasm for carcass yield when semi-intensively managed on humid, subtropical pasture. Results emphasize the importance of comparative breed evaluations to provide industry with reliable information on carcass yield among goat genotypes. [ABSTRACT FROM AUTHOR]

Growth, feed intake, and temperament indicator data, collected over 5 yr on a total of 1,141 to 1,183 mixed-breed steers, were used to estimate genetic and phenotypic parameters. All steers had a portion of either Hereford or Angus or both plus varying percentages also of Simmental, Charolais, Limousin, Gelbvieh, Red Angus and MARC III composite. Because the steers were slaughtered on various dates each year and thus the animals varied in days on feed, weight and feed data were adjusted to a 140-d feeding period basis. Adjustment of measures of feed efficiency (gain:feed, G:F or residual feed intake, RFI, intake adjusted for metabolic body size and gain) for body fatness recorded at harvest had little effect on results of analyses. Average daily gain was less heritable (0.26) than mid-test body weight (MBW; 0.35). Measures of feed intake had greater estimates of heritability with 140-d dry matter intake (DMI) at 0.40 and RFI at 0.52; heritability estimate for G:F was 0.27. Flight speed (FS), as an indicator of temperament, had an estimated heritability of 0.34 and repeatability of 0.63. As expected, strong genetic (0.86) correlation was estimated between ADG and MBW; genetic correlations were less strong between DMI and ADG or MBW (0.56 and 0.71). Residual feed intake and DMI had a genetic correlation of 0.66. Indexes for phenotypic RFI and genotypically restricted RFI (no correlation with gain) were compared to simple economic indexes incorporating feed intake and growth to elucidate expected selection responses under different criteria. In general, few breed differences were detected across the various measurements. Heterosis contributed to greater DMI, RFI, and MBW, but it did not significantly affect ADG, G:F or FS. Balancing output (growth) with input costs (feed) is needed in practicing selection, and FS would not be recommended as an indicator trait for selection to change feed efficiency. An index including gain and RFI produced the best economic outcome. [ABSTRACT FROM AUTHOR]

The objectives of this work were to estimate genetic effects for age and size at estimated time of first conception, and temperament in straightbred and crossbred heifers (n = 554) produced from Romosinuano, Brahman, and Angus cattle, and to evaluate first-parturition performance of heifers, including calf birth weight, occurrence of calving difficulty, occurrence of poor vigor in their newborn calves, and calf mortality. At approximately 7 mo of age, weaned heifers were pastured with Mashona or Tuli bulls until confirmed pregnant. Body weight, hip height, exit velocity (m/s), and chute temperament score (1 calm, no movement; 5 = continuous movement, struggling) were recorded at 28-d intervals until heifers averaged 19 mo of age. Age at first conception was estimated as age at calving minus 285 d. Regression analyses were used to estimate BW and hip height at age of first conception. Brahman heifers were older, heavier, and had greater hip height than other straightbred groups (P < 0.05) and most crossbred groups. Brahman and reciprocal Brahman-Angus heifers had greater (P < 0.05) exit velocity than Romosinuano and Angus heifers. Brahman sire and dam breed chute temperament scores were greater (P < 0.05) than those of all other breed groups. Estimates of heterosis for age at first conception were -53.7 ± 9.5 (-11%), -56 ± 10.1 (-11%), and -92.9 ± 11 d (- 18%) for Romosinuano-Brahman, Romosinuano-Angus, and Brahman-Angus, respectively (P < 0.01). Heterosis was detected (P < 0.04) for Romosinuano-Brahman for BW (12 ± 4.3 kg, 3.7%) and hip height (1.3 ± 0.6 cm, 1%) at first conception. Maternal heterosis for calf birth weight was 3.6 ± 0.5 (12%) and 2.4 ± 0.6 kg (8.6%) for Romosinuano-Angus and Brahman-Angus. In Romosinuano-Brahman and Brahman-Angus, heterosis for exit velocity was 0.23 ± 0.09 (10%) and 0.5 ± 0.1 m/s (21%). The direct breed effect of Romosinuano was to reduce age (-58.2 ± 18.9 d), BW (-57.6 ± 10.5 kg), and hip height (-2.6 ± 1.1 cm) at the time of first conception (P < 0.01), and the direct Brahman effects (P < 0.001) were large and numerically positive for these traits (169.8 ± 20.8 d, 93.3 ± 11.6 kg, and 14 ± 1.2 cm). Use of Romosinuano in crossbreeding programs with Brahman may be useful for decreasing the age at first conception. The larger birth weights of calves born to Romosinuano-Angus cross heifers would not be desirable in southern cow-calf operations. [ABSTRACT FROM AUTHOR]

Current genetic evaluations are performed separately for each breed. Multiple breed genetic evaluations, however, assume a common base among breeds, enabling producers to compare cattle of different breed makeup. Breed and heterosis effects are needed in a multibreed evaluation because databases maintained by breed associations include few crossbred animals, which may not be. enough to accurately estimate these effects. The objective of this study was to infer breed effects, maternal effects, direct heterosis effects, and maternal heterosis effects for growth and carcass traits using least squares means estimates from crossbreeding studies published in the literature from 1976 to 1996. The data set was formed by recording each least squares mean along with the breed composition, maternal breed composition, and direct and maternal heterozygosity. Each trait was analyzed using a single trait fixed effect model, which included study as a fixed effect and breed composition and heterozygosity as covariates. Breed solutions for each trait were expressed relative to the Angus breed. Direct breed effects for weaning weight ranged from -7.0 ± 0.67 kg (British Dairy) to 29.3 ± 0.74 kg (Simmental), and maternal effects ranged from -11.7 ± 0.24 kg (Hereford) to 31.1 ± 2.22 kg (Gelbvieh). Direct breed effects for birth weight ranged from -0.5 ± 0.14 kg (British Dairy) to 10.1 ± 0.46 kg (Continental Beef), and maternal effects ranged from -7.2 ± 0.13 kg (Brahman) to 6.0 ± 1.07 kg (Continental Beef). Direct breed effects ranged from -17.9 ± 1.64 kg (Brahman) to 21.6 ± 1.95 kg (Charolais), from -6.5 ± 1.29 kg (Brahman) to 55.8 ± 1.47 kg (Continental Beef), from -8.1 ± 0.48 cm² (Shorthorn) to 21.0 ± 0.48 cm² (Continental Beef), and from -1.1 ± 0.02 cm (Continental Beef) to 0 ± 0.00 cm (Angus) for postweaning BW gain, carcass weight, LM area, and fat thickness, respectively. The use of literature estimates to predict direct and maternal breed and heterosis effects may supplement their direct prediction in a multibreed evaluation. [ABSTRACT FROM AUTHOR]

Data from pure breeds, as well as reciprocal crosses of German Angus (GA) and Simmental (SIM) beef cattle, were used to estimate genetic parameters and to evaluate the suitability for crossbreeding in terms of increasing productivity. Traits of interest were calving difficulty, birth weight (BWT), weaning weight (WWT), and ADG from birth to weaning. Data were collected over a period of 7 yr from 1997 and 1998 until 2003 and 2004, whereas crossbreeding was carried out in 2002 and 2003, and 2003 and 2004 only. Variance components and differences between breeds, individual heterosis, and maternal breed effects were analyzed based on 1,441 purebred and 329 crossbred records for BWT and 1,319 purebred and 316 crossbred records for WWT and ADG, respectively. Mean calving difficulty scores were greater in SIM than in GA (P < 0.001). For BWT, WWT, and ADG both reciprocal crosses fell between the purebreds, and for all 3 traits SIM showed greater average values compared with GA. The estimated heritabilities were 0.23 for BWT and 0.12 for WWT. Values for the maternal effect and the correlation between additive and maternal effect were 0.18 for BWT, 0.08 for WWT, 0.32 for BWT, and 0.50 for WWT, respectively. Individual heterosis was only significant for BWT (3.7%; P < 0.01). Superior mothering ability of SIM was implicated by greater WWT and ADG of SIM as dam against the reciprocal cross (P <0.001). The results provide information about the ex tent of individual heterosis and maternal breed effects. [ABSTRACT FROM AUTHOR]

ABSTRACT: For 75 yr, Line 1 Hereford cattle have been at the forefront of beef cattle breeding research. The goal of this review is to provide an overview of scientific contributions made using the Line 1 Hereford population. It was initially developed as contribution to a western regional program from which beef producers were envisioned to use heterosis by crossing selected inbred lines. Whereas this vision was never fulfilled, being largely supplanted by crossbreeding, Line 1 has had a profound influence on beef cattle breeding research and the Hereford breed. For more than 60 yr, Hereford breeders and commercial beef producers have purchased Line 1 Hereford gerrnplasrn for use in their herds. By example, Line 1 illustrates a successful linebreeding program through which a 39% additive relationship to the founding sire has been maintained over rnore than 18 generations. Procedures for performance testing beef cattle can be traced to original research with Line 1. Data from Line 1 contributed to the first estimates of heritability and genetic correlation for beef cattle. Work with Line 1 has also contributed greatly to the understanding of maternal genetic effects in beef cattle. Diallel crossing with other inbred lines provided early estimates of heterosis for beef cattle, complimented by the later observation that heterosis resulted in complete recovery of the accumulated negative effects of inbreeding. After exchanges of germplasm with the Northern Montana Agricultural Experiment Station at Havre and the Brooksville Beef Cattle Research Station in Florida, pioneering comprehensive evaluations of genotype x environment interaction were condi.icted. Breeding practices implemented by USDA Agricultural Research Service at Miles City make Line 1 the longest running selection experiment using beef cattle worldwide. This long-term database has provided an exceptional resource for prototype evaluations of procedures for national cattle evaluation, and the results make up an integral part of the foundation of modern-day genetic evaluation programs. Having used DNA from Line 1 in the development of a bacterial artificial chromosome library and the bovine genome sequence, Line 1 Hereford cattle are uniquely positioned for continued contributions in future research. [ABSTRACT FROM AUTHOR]

Twenty-five genetic groups of young rabbits originated from a diallel-crossbreeding scheme among 5 selected lines: 3 maternal and 2 terminal sire lines belonging to 2 Spanish research institutions. A sample of 2,773 young rabbits from 525 litters was controlled during the fattening period lasting from 5 to 9 wk. Growth and feed consumption traits were evaluated throug-out different biweekly batches. A Bayesian approach was used for inference from an animal model with common litter effects. On average, genetic groups coming from lines selected for growth rate were heavier (+58.9 g at 32 d and +315.5 g at 60 d), had greater growth rate (9.24 and 8.15 g/d from individual or cage analysis, respectively) and feed intake (+13.24 g/d), and showed better feed conversion ratio (-0.21 g of intake/g of gain), than the genetic groups originated from crosses among lines selected for litter size. Crossbreeding parameters were estimated from the sample, of the marginal posterior distribution of the genetic group effect according to the Dickerson model. Maternal genetic and individual heterosis effects were null or very low. Direct genetic effects mainly regulated the expression of growth traits. [ABSTRACT FROM AUTHOR]

The overall motivation for the development of an information system for beef cattle improvement is the belief that knowledge of breeding values and heterosis effects allows one to determine the consequences of alternative selection and mating options. With this information, livestock managers can easily shift populations in a desirable direction. The foundation principles for establishing a sound breeding program, including the prediction of animal performance for economically relevant traits and their incorporation into a single index of aggregate economic merit, have been well established over the last half century. Rather than this goal-based approach, the industry adopted a data-driven approach to the production of genetic evaluations that has been characterized by an overemphasis on the evaluation of productive traits, notably BW at various ages, with inadequate regard for other economically important traits, such as reproduction, animal health, and feed requirements. Production of evaluations is breed association centered, and this has delayed the introduction of national across-breed evaluations for all breeds and crosses of cattle. The computational aspects of producing evaluations are now migrating from land-grant universities to breed associations, but not yet to a single entity. The introduction of genomic information in the form of high-density SNP panels will introduce threats, challenges, and new opportunities for the production of evaluations, and represents the largest force to alter the structure of the beef improvement industry since the advent of AI. The use of evaluations has, until recently, stopped short of the provision of index merit as a basis for selection. Accordingly, the value propositions associated with annual improvement or the selection of alternative sires has not been well communicated. Technology, along with economic and other issues related to stakeholder acceptance, will collectively determine the future nature of the industry in terms of the production and use of evaluations. [ABSTRACT FROM AUTHOR]

The objective herein was to estimate heterosis and breed effects in purebred and crossbred Romosinuano, Brahman, and Angus calves on acute phase protein response to weaning and transportation. Calves (n = 1,032) were weaned in September of 2002, 2003, and 2004 at approximately 7 mo of age. Approximately 28 d after weaning, steer calves (n = 482) were transported 1,800 km (20 h) to Oklahoma. Concentrations of 3 acute phase proteins (ceruloplasmin, fibrinogen, and haptoglobin) were measured in blood samples. Calves (steers and heifers) were sampled at weaning, and 24 and 72 h postweaning. For separate analyses, steers sent to Oklahoma were sampled before shipment, upon arrival, and 24 and 72 h after arrival. Combinations of the following fixed effects were investigated: sire breed, dam breed, sampling time, birth location, calf sex (weaning only), year, cow age, and interactions. Effects of special interest were sire breed × dam breed as an indication of breed group of calf, and the interaction of sire and dam breeds with sampling time. Weaning age and BW were investigated as linear and quadratic covariates. Sire of calf within sire breed was a random term. The correlation structure of repeated measures was determined by comparison of information criterion values for different structures within each analysis. In general, plasma acute phase protein concentrations in weaned calves increased with sampling time. Concentrations in the transported steers increased through sampling at 24 h after arrival, and were lower at 72 h. Significant estimates of heterosis were detected for Brahman-Angus haptoglobin concentrations at weaning (0.38 ± 0.14 mg/dL × 100; 44%), and for Romosinuano-Angus fibrinogen concentrations at weaning (11.4 ± 5.5 mg/dL; 10%) and in transported steers (22.5 ± 8.4 mg/dL; 20%). The direct effect of Romosinuano was to increase (P < 0.004) ceruloplasmin concentrations of weaned calves (4.1 ± 0.9 mg/dL) and of transported steers (3.9 ± 1.3 mg/dL). The direct effect of Angus was to lower ceruloplasmin concentrations in weaned calves (-3.9 ± 1.2; P = 0.001). Significant maternal effects were detected at weaning for ceruloplasmin concentrations in Romosinuano (-1.4 ± 0.5 mg/dL) and Angus (1.6 ± 0.7 mg/dL) and fibrinogen concentrations in Brahman calves (-17.7 ± 8.8 mg/dL). These data imply that acute phase protein concentrations in response to weaning and transportation are impacted by cattle breed. [ABSTRACT FROM AUTHOR]

The objectives of this work were to evaluate birth and weaning traits, to estimate genetic effects, including heterosis and direct and maternal breed effects, and to evaluate calving difficulty, calf vigor at birth, and calf mortality of Romosinuano as purebreds and as crosses with Brahman and Angus. Calves (n = 1,348) were spring-born from 2002 through 2005 and weaned in the fall of each year at about 7 mo of age. Traits evaluated included birth and weaning weight, ADG, BCS, and weaning hip height. Models used to analyze these traits included the fixed effects of year, sire and dam breeds, management unit, calf sex, cow age, and source of Angus sire (within or outside of the research herd). Calf age in days was investigated as a covariate for weaning traits. Sire within sire breed and dam within dam breed were random effects. Estimates of Romosinuano-Brahman and Romosinuano-Angus heterosis (P < 0.05) were 2.6 ± 0.3 (8.6%) and 1.4 ± 0.3 kg (4.7%) for birth weight, 20.5 ± 1.5 (9.5%) and 14.6 ± 1.4 kg (7.4%) for weaning weight, 79.2 ± 6.1 (9.8%) and 55.1 ± 6.0 g (7.5%) for ADG, 0.16 ± 0.03 (2.7%) and 0.07 ± 0.03 (1.2%) for BCS, and 2.77 ± 0.32 cm (2.4%) and 1.87 ± 0.32 cm (1.7%) for hip height. Heterosis for Brahman-Angus was greater (P < 0.05) than all Romosinuano estimates except those for Romosinuano-Brahman and Romosinuano-Angus BCS. Romosinuano direct effects were negative and lowest of the breeds, except for the Angus estimate for hip height. Romosinuano maternal effects were the largest of the 3 breeds for birth weight and hip height but intermediate to the other breeds for weaning weight and ADG. A large proportion of Brahman-sired calves from Angus dams (0.09 ± 0.03; n = 11) was born in difficult births and died before 4 d of age. Brahman and Angus purebreds and Romosinuano-sired calves from Brahman dams also had large proportions of calves that died before weaning (0.09 or greater). Results indicated that Romosinuano may be used as a source of adaptation to subtropical environments and still incorporate substantial crossbred advantage for weaning traits, although not to the extent of crosses of Brahman and Angus. [ABSTRACT FROM AUTHOR]

Additive and nonadditive genetic effects on preweaning weight gain (PWG) of a commercial crossbred population were estimated using different genetic models and estimation methods. The data set consisted of 103,445 records on purebred and crossbred Nelore-Hereford calves raised under pasture conditions on farms located in south, southeast, and middle west Brazilian regions. In addition to breed additive and dominance effects, the models including different epistasis covariables were tested. Models considering joint additive and environment (latitude) by genetic effects interactions were also applied. In a first step, analyses were carried out under animal models. In a second step, preadjusted records were analyzed using ordinary least squares (OLS) and ridge regression (RR). The results reinforced evidence that breed additive and dominance effects are not sufficient to explain the observed vanability in preweaning traits of Bos taurus × Bos indicus calves, and that genotype × environment interaction plays an important role in the evaluation of crossbred calves. Data were ill-conditioned to estimate the effects of genotype × environment interactions. Models including these effects presented multicolinearity problems. In this case, RR seemed to be a powerful tool for obtaining more plausible and stable estimates. Estimated prediction error variances and variance inflation factors were drastically reduced, and many effects that were not significant under ordinary least squares became significant under RR. Predictions of PWG based on RR estimates were more acceptable from a biological perspective. In temperate and subtropical regions, calves with intermediate genetic compositions (close to ½ Nelore) exhibited greater predicted PWG. In the tropics, predicted PWG increased linearly as genotype got closer to Nelore. [ABSTRACT FROM AUTHOR]