Search

Background: No dairy breed or crossbreed has superior overall performance in all environments; therefore, it is necessary to determine which crossbreed is the most suitable for the Mexican tropic and what proportion of European breed is optimum for reproduction. Objective: To assess the effect of the proportion of Bos taurus (Bt) genes on reproductive performance of Holstein×Zebu (HZ) and Brown Swiss×Zebu (BZ) cows, and compare reproductive performance of these genotypes in a dualpurpose production system. Methods: Cows were maintained in a rotational grazing system on African star grass (Cynodon plectostachyus) in Veracruz, Mexico. Cows were milked twice daily. Calves were kept tied to the side of their dams while the cows were milked. Results: The percentage of Bt genes did not affect (p>0.05) fertility traits (age at first calving, days to first service after calving, services per conception, conception rate at first service, days open until conception, gestation length, and calving interval) of BZ cows. In contrast, HZ cows with less than 75% Holstein (H) genes were 0.3 years younger (p<0.05) at first calving and had 39.8 fewer days open (p<0.05) than HZ cows with 75% H genes or more. In addition, the calving interval of HZ cows with less than 75% H genes was 44.8 days shorter (p<0.05) than that of HZ cows with 75% H genes or more. The HZ cows had five fewer days pregnant and were 22.8 kg heavier at calving (p<0.05) than BZ cows. Conclusions: The effect of the percentage of Bt genes on cow fertility depends on the dairy breed used. In general, BZ and HZ cows present similar reproductive performance. [ABSTRACT FROM AUTHOR]

The National Institute of Forestry, Agricultural and Livestock Research (INIFAP) in Mexico has been studying the Criollo Coreño (C) cattle of the Sierra Madre Occidental for over 20 yr. This review covers productive, genetic and molecular characterization, as well as short-, medium- long-term research challenges and outlooks. Evaluations have been done of 35 growth, carcass quality, fertility and milk production traits in C, Guzerat (G), CG and GC cattle generated through diallelic crossing. Individual heterosis was found to affect reproduction and milk production, while maternal heterosis influenced kilograms of calf weaned per cow exposed. Direct and maternal genetic effects had no relevant influence on the analyzed variables. In other studies, C bulls fed high energy diets were found to produce meat with favorable fatty acid profiles and good quality carcasses, while low doses of FSH can be used for superovulation in C heifers, without affecting embryo production. Overall, the results indicate that GC cows are the best option for calf production, and that the C population maintains significant levels of genetic diversity. Further genetic diversity research is needed on Mexican Criollo cattle populations using molecular genetics; Criollo herds must be included in the systematic recording of phenotypes of productivity and adaptability to be able to identify genes of interest unique to Criollo cattle. [ABSTRACT FROM AUTHOR]

The National Institute of Forestry, Agricultural and Livestock Research in Mexico has been active for decades in researching genetic improvement in beef cattle. This review uses master theses, congress papers and scientific articles published from 1987 to 2020 to summarize much of the relevant research, and addresses research challenges and outlook over the short-, medium- and long-term in this area. Research done over the last 34 yr has evaluated the productive and reproductive performance of Bos indicus and Bos taurus x Bos indicus beef cattle raised under tropical conditions. Multibreed genetic evaluations have been done for Simmental-Simbrah and Charolais-Charbray populations in Mexico. Analyses have quantified the importance of maternal effects on growth traits, and estimated heritability and genetic correlations for growth and reproductive traits in male and female Bos taurus and Bos indicus animals. The genotype-environment interaction has been confirmed to influence expression of weaning weight in Simmental cattle. Age adjustment factors have been developed for maternal age for weights at birth and weaning, and prototypes of national genetic evaluation were developed for stayability and heifer fertility. Genetic diversity has been quantified for Simmental, Charolais and Simbrah populations, and SNPs identified that are associated with growth traits in Simmental and Simbrah populations. Short-term goals include development of selection indices and prediction of the genetic merit of carcass traits. Over the medium-term, emphasis is needed on genomic evaluations for tolerance to heat stress, residual feed intake and health traits, while in the long-term the goal is to make interbreed genomic predictions. [ABSTRACT FROM AUTHOR]

The objective was to compare the prevalences of antibodies against different serovars of Leptospira interrogans among the states of Puebla, Tabasco and Ve racruz, as well as among some of their municipalities, and to determine if the health status of the cows influences their fertility. Blood samples were taken from 423 cows ( Bos taurus x Bos indicus and Bos indicus ) from 24 ranches in 11 municipalities in t he aforementioned states. The prevalences of the Hardjo and Inifap serovars were higher ( P <0.05) in the state of Veracruz than in the state of Puebla, but the prevalence of the Wolffi serovar was higher ( P <0.05) in the state of Puebla than in the state of Veracruz. The prevalences of the Hardjo and Palo Alto serovars were higher ( P <0.05) in the state of Tabasco than in the state of Puebla, but there were no differences between these two states in the prevalences of the Inifap and Wolffi serovars ( P >0.05). The number of serovars in the state of Veracruz was higher ( P <0.05) than in the state of Puebla, but the number of serovars in Tabasco was intermediate; in addition, there was an important variation ( P <0.05) between municipalities and between ranch es in the prevalence of the different serovars. Overall, the serovar with the highest frequency was Inifap, while the serovar with the lowest frequency was Tarassovi. The health status of the cows did not influence the pregnancy rate ( P >0.05); however, vac cination of cattle against Leptospira interrogans is recommended in order to decrease the risks associated with this bacterium in cattle and humans. [ABSTRACT FROM AUTHOR]

Objective: The aim was to characterize the genetic diversity evolution of the registered Mexican Charolais cattle population by pedigree analysis. Methods: Data consisted of 331,390 pedigree records of animals born from 1934 to 2018. Average complete generation equivalent, generation interval, effective population size (Ne), and effective numbers of founders (fe), ancestors (fa), and founder genomes (Ng) were calculated for seven five-year periods. The inbreeding coefficient was calculated per year of birth, from 1984 to 2018, whereas the gene contribution of the most influential ancestors was calculated for the latter period. Results: Average complete generation equivalent consistently increased across periods, from 4.76, for the first period (1984 through 1988), to 7.86, for the last period (2014 through 2018). The inbreeding coefficient showed a relative steadiness across the last seventeen years, oscillating from 0.0110 to 0.0145. During the last period, the average generation interval for the father-offspring pathways was nearly 1 yr. longer than that of the mother-offspring pathways. The effective population size increased steadily since 1984 (105.0) and until 2013 (237.1), but showed a minor decline from 2013 to 2018 (233.2). The population displayed an increase in the fa since 1984 and until 2008; however, showed a small decrease during the last decade. The effective number of founder genomes increased from 1984 to 2003, but revealed loss of genetic variability during the last fifteen years (from 136.4 to 127.7). The fa:fe ratio suggests that the genetic diversity loss was partially caused by formation of genetic bottlenecks in the pedigree; in addition, the Ng:fa ratio indicates loss of founder alleles due to genetic drift. The most influential ancestor explained 1.8% of the total genetic variability in the progeny born from 2014 to 2018. Conclusion: Inbreeding, Ne, fa, and Ng are rather beyond critical levels; therefore, the current genetic status of the population is not at risk. [ABSTRACT FROM AUTHOR]

Objective. Compare the fertility of Brown Swiss x Zebu and Simmental x Zebu crossbred cows reared in a tropical environment. Materials and methods. Reproductive traits of 185 Brown Swiss x Zebu and Simmental x Zebu crossbred cows with diverse percentages of European breed were evaluated. Grazing of cows was rotational. The milking was twice daily with the help (suckling) of the calf, which was kept tied next to the dam while she was milked. Traits were evaluated fitting a repeated measures model (except for age at first calving). Calving interval, age at first calving, days open, interval from calving to first service, and weight at calving were analyzed with PROC MIXED of SAS. Pregnancy rate at first service and services per conception were analyzed with PROC GENMOD of the same software. Results. Simmental x Zebu cows started to re-bred 39 days earlier after calving (p<0.05) and had 47 fewer days open (p<0.05) than Brown Swiss x Zebu cows. The calving interval of the Simmental x Zebu cows was 45 days shorter (p<0.05) than that of the Brown Swiss x Zebu cows. Simmental x Zebu cows were 34 kg heavier at calving (p<0.05) than Brown Swiss x Zebu cows. Conclusions. Simmental x Zebu cows had better fertility than Brown Swiss x Zebu cows. [ABSTRACT FROM AUTHOR]

• Yearling weight showed the highest chance for genetic progress in the long term. • Heritability for age at first calving was greater than that for heifer fertility. • Direct selection to increase yearling weight would increase frame score. • Direct selection for younger age at first calving would improve heifer fertility. • For frame score, direct response was greater than correlated response to selection. The objective was to estimate heritability, genetic correlations and expected genetic superiority (EGS) by direct selection, and expected correlated genetic superiority of selected sires for yearling weight (YW), frame score (FS), age at first calving (AFC) and heifer fertility (HF) of Mexican Charolais females. Records were provided by the Charolais-Charbray Herd Book de México. Estimates of (co)variance components were estimated applying a four-trait animal model that included direct genetic effect, contemporary group, and the linear and quadratic effect of dam age, except for AFC. Heritability estimates were 0.18, 0.13, 0.15, and 0.13 for YW, FS, AFC and HF, respectively. Genetic correlations (r2) estimates were 0.60, -0.14, 0.14, -0.24, 0.26 and -0.92 for YW-FS, YW-AFC, YW-HF, FS-AFC, FS-HF and AFC HF, respectively. The EGS with 5 and 500 half-sib progeny per sire was 4.72 and 10.58, 0.10 and 0.26, 23.98 and 57.92, and 0.15 and 0.38 for YW, FS, AFC and HF, respectively. The moderate r2 for YW-FS suggests that direct selection to increase YW would increase FS. The strong r2 for AFC HF indicates that direct selection to decrease AFC would improve HF. The low r2 for YW-AFC and YW-HF indicate direct selection for YW would not alter AFC and HF. [ABSTRACT FROM AUTHOR]

Background: Knowledge of genetic correlations and the economics of traits are essential to decide which traits should be used as selection criteria. Objective: To estimate heritabilities and genetic, environmental, and phenotypic correlations, and direct (DRS) and correlated (CRS) responses to selection by scrotal circumference (SC), frame score (FS), and yearling weight (YW) of Mexican Charolais (CH), and Charbray (CB) young bulls. Methods: Actual SC, height and YW records (10,078 for CH, and 500 for CB) were adjusted to 365 d. The 0.0505 adjustment factor recommended by the Beef Improvement Federation was used to obtain the 365-d adjusted SC for both breeds. Height and age records were used to obtain FS. Data were analyzed using a three-trait animal model. The animal model for each trait included bull breed, contemporary group (groups of young bulls born in the same herd, year, and season of the year), and age of dam as a linear covariate as fixed effects, and direct additive genetic and residual as random effects. Results: Heritability estimates for SC, FS and YW were 0.21 ± 0.04, 0.25 ± 0.04, and 0.29 ± 0.04, respectively. The genetic correlation between YW with SC was 0.37 ± 0.16, and between YW with FS was 0.42 ± 0.16. The estimate of genetic correlation between SC and FS was low and positive (0.15 ± 0.14). The DRS was 0.38 cm, 0.18 units, and 8.30 kg for SC, FS and YW. The CRS was 0.16 cm, and 0.08 units for SC and FS from indirect selection on YW. Conclusions: Direct selection for YW is expected to be effective. Indirect selection for SC and FS based on YW would not be expected to be as effective as direct selection for improving SC and FS. [ABSTRACT FROM AUTHOR]

The objective was to evaluate some morphological characteristics of backyard turkeys (n=248) coming from 126 rural production units located in 75 municipalities of 24 States of the Mexican Republic. The statistical model included sex, state, and municipality within state. The three explanatory variables affected all the response variables (P<0.01), except municipality, which did not affect breast circumference (P>0.05). Male turkeys had greater (P<0.001) body length (10.7 cm more), wingspan (11.4 cm more), breast circumference (13.8 cm more), shank length (2.5 cm more), body weight (2.5 kg more), stockiness (9.0 percentage units more) and massiveness (2.8 percentage units more) than female turkeys. Body weight showed to be highly correlated phenotypically (P<0.01) with breast circumference in both males (r=0.74) and females (r=0.71). Body length was lowly correlated with shank length (r=0.25; P<0.01) in males, but it was not correlated with shank length in females (r=0.05; P>0.05). Body weight increased 143 g in males (P<0.01) and 113 g in females (P<0.01) for each centimeter increment in breast circumference. The predominant colors in the plumage, skin and tarsus were black, white and brown, respectively. The Mexican backyard turkey presented significant sexual dimorphism and strong phenotypic correlation between breast circumference and body weight. [ABSTRACT FROM AUTHOR]

The objective of the present study was to determine the milk yield of Simmental-Zebu and Brown Swiss-Zebu cows with different proportions of Bos taurus genes. The study was carried out from 1985 to 2007 at the the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Playa Vicente research station (Veracruz, Mexico). The site presents a humid tropical climate. Milk yield records of Simmental x Zebu and Brown Swiss x Zebu cows with different proportions of Bos taurus genes (50, 62.5 or 75%) were analyzed. The cows were maintained in rotational grazing of the introduced pastures: Star grass (Cynodon plectostachyus) and Guinea (Panicum maximum), and were milked twice a day, after a restricted suckling by their calves. Calves were weaned at 210 days of age. The statistical model included the fixed effects of breed group, year of calving, season of calving, lactation number, and lactation length as a linear covariate; in addition, the model included sire of the cow within breed group as a random effect. The lactation length of Brown Swiss x Zebu cows was greater (P<0.05) than that of Simmental x Zebu cows. Milk yield per lactation, per day and per calving interval of Simmental x Zebu and Brown Swiss x Zebu cows were similar. Third-parity cows yielded more milk (P<0.001) per lactation, per day and per calving interval than first- and second-parity cows. Second-parity cows yielded more milk (P<0.001) per lactation, per day and per calving interval than first-parity cows. [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate variance components and genetic parameters for age at first service (AFS), age at first calving (AFC), gestation length (GL), days open (DO), calving interval (CI), services per conception (SPC) and cow weight at calving (CW) of lndubrazil cows (N=264) born from 1974 to 2004. The study was carried out at the Playa Vicente research station (Veracruz, México) from Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP). The cows were bred twice a year, in spring and autumn. The breeding seasons initiated on April 1 and October 1, and ended on June 30 and November 30, respectively. Age at first service, AFC, GL, DO, CI and SPC were analyzed with an animal model that included the additive genetic effect, while CW was analyzed with a repeatability animal model that included the additive genetic effect and the permanent environmental effect of the cow. The analyses were carried out with the MTDFREML program. The estimates of heritability were: 0.31 ± 0.152, 0.39 ± 0.196, 0.08 ± 0.033, 0.03 ± 0.028, 0.13 ± 0.056, 0.03 ± 0.027 and 0.49 ± 0.098 for AFS, AFC, GL, DO, CI, SPC and CW, respectively. The permanent environmental effect of the cow explained 2% of the total phenotypic variance of CW, hence the estimate of repeatability for this trait was 0.51. Age at first service, AFC, CI and CW showed substantial genetic variation; therefore, they could be considered in a selection program. [ABSTRACT FROM AUTHOR]

The objective of this work was to estimate the heritability and repeatability of reproductive traits of Holstein cows reared in subtropical conditions. Records from 171 cows were analyzed, which were daughters of 67 sires and 100 dams. The cows were born from 1986 to 2006, in Las Margaritas research station from the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), in Hueytamalco, Puebla, Mexico. Genetic parameters were estimated for interval from calving to first registered heat, interval from calving to first registered service, number of services per conception, days open, and calving interval. Variance components for interval from calving to first registered heat, interval from calving to first registered service, days open, and calving interval were estimated with a single-trait repeatability animal model, while variance components for number of services per conception were estimated with a single-trait animal model, which included the direct additive genetic effect as a random effect. Variance components were estimated with derivative- free restricted maximum likelihood using the MTDFREML program. Estimates of heritability were low, from 0,01 (days open) to 0.13 (calving interval). Estimates of repeatability were also low, ranging from 0.11 (interval from calving to first registered service) to 0.16 (days open). In general, estimates of heritability and repeatability obtained are within the interval of estimates reported in the scientific literature. Estimates of genetic parameters indicate that direct response to one-trait selection would be slow. [ABSTRACT FROM AUTHOR]

The objective of this work was to estimate the genetic and phenotypic correlations among fertility traits of 317 Holstein Friesian and Brown Swiss cows. Cows were born and reared under subtropical conditions, during a 20-year period (1986 to 2006), and were daughters of 116 sires and 199 dams. The study was carried out in Las Margaritas research station, in Hueytamalco, Puebla, México, which belongs to the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP). Fertility traits studied were: days to first service after calving (DFS), calving interval (CI), days open (DO), number of services per conception (NSC) and conception rate at first service (CR). Genetic correlations were estimated with a two-trait animal model (bivariate analysis), which included individual additive genetic effect as a sole random effect. Main fixed effects were: calving year, calving season and breed of cow. Analyses were carried out with restricted maximum likelihood, using an algorithm free of derivatives. In general, fertility traits were favorably and strongly correlated genetically. Estimates of genetic correlations for DFS-CI, DFS-DO, DFS-NSC, CI-DO, CI-NSC, and DO-NSC were positive (0,89, 0,89, 0,25, 0,90, 0,59 and 0,97, respectively), while all estimates of genetic correlations that included conception rate to first service (DFS-CR, CI-CR, DO-CR, NSC-CR) were negative (-0,45, -0,62, -0,72, -0,85). The high estimates of genetic correlations between CI and DFS or DO indicate that selection for less DFS or DO would reduce CI. [ABSTRACT FROM AUTHOR]

Objective. To evaluate the reproductive performance of crossbred cows in the tropics of Mexico fed two levels of neutral detergent fiber (NDF), eliciting them to ovulate with a hormonal protocol and fixed-time artificial insemination (FTAI). Material and methods. Twenty-seven multiparous cows were used. Twenty-one days before calving, cows were assigned to two treatments: T1=4.5 kg of concentrate/cow/d and T2= 3.0 kg of concentrate/cow/d, and forage ad libitum in both treatments. Results. Cows assigned to T2 consumed more NDF (p<0.05) than cows assigned to T1 (38 vs 44% of the diet). The increment in forage consumption, up to the NDF allowed, compensated the provision of metabolizable energy (ME) and protein (MP), which were similar in cows of both treatments during the 15 days before calving. Cows fed with T2 tried to compensate the nutrients deficit consuming more forage (6.25 vs 7.37 kg of DM/d). The MP was always deficient during lactation for T1 and T2 cows. In T2 cows, the MP deficiency resulted in less milk nitrogen content. Cows assigned to T1 lost less body condition, which resulted in higher (p<0.05) pregnancy rate at first service (75.2 vs 42.8%), although they did not produce more milk than T2 cows. Conclusions. NDF reduction in the ration from 44 to 38% and the application of the FTAI hormonal protocol reduce the open period to 105 d in lactating cows in the tropics. [ABSTRACT FROM AUTHOR]

Reproductive efficiency stands as a critical determinant of profitability within beef production systems. The incorporation of molecular markers can expedite advancements in reproductive performance. While the use of SNPs in association analysis is prevalent, approaches centered on haplotypes can offer a more comprehensive insight. The study used registered Simmental and Simbrah cattle genotyped with the GGP Bovine 150 k panel. Phenotypes included scrotal circumference (SC), heifer fertility (HF), stayability (STAY), and frame score (FS). After quality control, 105,129 autosomal SNPs from 967 animals were used. Haplotype blocks were defined based on linkage disequilibrium. Comparison between haplotypes and SNPs for reproductive traits and FS was conducted using Bayesian and frequentist models. 23, 13, 7, and 2 SNPs exhibited associations with FS, SC, HF, and STAY, respectively. In addition, seven, eight, seven, and one haplotypes displayed associations with FS, SC, HF, and STAY, respectively. Within these delineated genomic segments, potential candidate genes were associated. [ABSTRACT FROM AUTHOR]

Objective. To evaluate pre-weaning growth traits of Angus-, Brahman- and Akaushi-sired calves. Materials and methods. One-hundred seventy one calves were produced by artificial insemination in nine herds in the state of Puebla (subtropical environment; n=83) and four herds in the state of Veracruz (tropical environment; n=88), Mexico. Eleven Angus, 15 Brahman, and 5 Akaushi bulls, sired the calves. Average age at weaning was 219 days. The analyses were carried out with the MIXED procedure of SAS. The model included the effects of breed of sire, sex of calf, birth season, state of the country, and herd nested within state. In addition, the model for actual weaning weight included the linear effect of calf age at weaning. Results. Brahman-sired calves were heavier at birth (p<0.05) than Angus- and Akaushi-sired calves; however, Angus-, Brahman- and Akaushi-sired calves had similar average daily gains from birth to weaning (p>0.05). Angus- and Akaushi-sired calves had similar actual weaning weights (p>0.05), but Brahman-sired calves were heavier at weaning (p<0.05) than Akaushi-sired calves. Sex of calf and season of birth were not significant sources of variation (p>0.05) for any trait. Calves reared in subtropical conditions were heavier at weaning (p<0.05) than those reared in tropical conditions. Conclusions. In general, Brahman-sired calves had a better pre-weaning performance than Angus- and Akaushi-sired calves. [ABSTRACT FROM AUTHOR]

Crossbreeding allows taking advantage of additive genetic differences between breeds, they also allow making use of heterosis and complementarity. Therefore, it is necessary to generate information on the efficacy of crosses compared to pure breeds under the conditions of interest. The objective was to quantify the impact of additive and non-additive genetic effects for days to first estrus (DFE), days to first service (DFS), days open (DO), services per conception (SPC), calving interval (CI) and gestation length (GL). The productive and genealogical information of females from a diallel between Holstein (HO) and Brown Swiss (BS), a total of 148 cows of the breeds HO (n=43), BS (n=64) and their reciprocal crosses HO-BS (n=20) and BS-HO (n=21), was used. Contrasts were used to estimate individual heterosis and differences between direct genetic effects and between maternal genetic effects based on Dickerson models. The results showed that heterosis and differences between maternal effects were not significant (P>0.05) for any of the traits studied. Differences between direct genetic effects were only important (P<0.05) for SPC and GL. In conclusion, the heterosis generated by the crossbreeding between HO and BS did not influence the reproductive efficiency of females. Maternal effects were not different between HO and BS. Direct genetic effects for SPC and GL favored the BS breed. [ABSTRACT FROM AUTHOR]

Objective: In tropical, subtropical and arid zones, heat stress is the main cause of productivity reduction in cattle. When climate stressors occur, animals become thermal adapted through differential expression of some genes, including heat shock proteins (HSP) family. The aim of this study was to determine levels of expression of HSP60, HSP70, and HSP90 genes in Simmental cattle raised in tropical environments of Mexico. Methods: In this study, expression of HSP60, HSP70, and HSP90 genes was analyzed in 116 Simmental cattle from three farms with tropical climate located in western Mexico. Animals were sampled twice a day, in the morning and noon. Gene expression was evaluated by quantitative polymerase chain reaction using probes marked with fluorescence. The MIXED procedure of SAS with repeated measures was used for all statistical analysis. Results: HSP60 gene expression differences were found for sex (p = 0.0349). HSP70 gene differences were detected for sampling hour (p = 0.0042), farm (p<0.0001), sex (p = 0.0476), and the interaction sampling hour×farm (p = 0.0002). Gene expression differences for HSP90 were observed for farm (p<0.0001) and year (p = 0.0521). HSP70 gene showed to be a better marker of heat stress than HSP60 and HSP90 genes. Conclusion: Expression of HSP70 gene in Simmental herds of the tropical region of western México was different during early morning and noon, but the expression of the HSP60 and HSP90 genes was similar. Identification of resilient animals to heat stress will be useful in the genetic improvement of the Simmental breed. [ABSTRACT FROM AUTHOR]

El objetivo fue determinar la prevalencia de anticuerpos séricos (PAS) en respuesta a la vacunación contra los virus de la rinotraqueitis infecciosa bovina (RIB) y diarrea viral bovina (DVB) en vacas lecheras en condiciones subtropicales. Se utilizó una vacuna polivalente comercial con virus inactivado de la DVB y virus activos modificados de la RIB, parainfluenza 3 y síndrome respiratorio bovino. Se formaron dos grupos: grupo experimental vacunado (GEV) y no vacunado (GEN), que fueron homogéneos en PAS contra RIB y DVB antes de la vacunación. El GEV se inmunizó el día 0 y el día 30 después de la primera vacunación (vacuna de refuerzo). Para detectar anticuerpos, se obtuvieron muestras de suero 30 días después de la primera y segunda vacunación. Los anticuerpos séricos contra RIB y DVB se determinaron mediante la prueba de ELISA. La PAS promedio contra RIB y DVB antes de la vacunación fue 16 (18 % en el GEV vs 14 % en el GEN; P>0.05) y 8 % (10 % en el GEV vs 6 % en el GEN; P>0.05), respectivamente. La primera y segunda vacunación contra RIB indujeron la formación de anticuerpos 30 días después de su aplicación; con la primera vacunación, la PAS en las vacas vacunadas fue 36 unidades porcentuales mayor (P<0.05) que en las no vacunadas (58 vs 22 %) y con la vacuna de refuerzo, la PAS en las vacas vacunadas fue 66 unidades porcentuales mayor (P<0.05) que en las no vacunadas (94 vs 28 %). La vacuna comercial no indujo la producción de anticuerpos contra DVB con ninguna de las dos inmunizaciones. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop a prototype of multibreed genetic evaluation for heifers' fertility (FERT) in Simmental-Simbrah and Charolais-Charbray populations. Information from 49,943 Simmental-Simbrah females born between 1984 and 2011 (EvSim) and 49,871 Charolais and Charbray females (EvChar), born between 1990 and 2011 were used. For the analysis, a one was assigned when a heifer calved before 1,281 d of age, otherwise a zero was assigned. Variance components estimates and breeding values were obtained by fitting a linear mixed model for a single trait. Estimates of heritability were similar, 0.07 ± 0.008 and 0.06 ± 0.008, for EvSim and EvChar, respectively. Median number of heifers per contemporary group was 10, with an interquartile range from 5 to 20, in both cases, EvSim and EvChar. Median number of paternal half sibs per family was 5 for both, EvSim and EvChar. The ranges of expected progeny differences (EPD) for FERT were: -5.79 to 8.72, -9.56 to 8.84, -7.94 to 8.22, and -7.29 to 6.14, for Simmental, Simbrah, Charolais and Charbray, respectively. Heritability estimates suggest that there may be genetic response to selection of FERT in the populations evaluated. Estimated genetic trends suggest a favorable genetic change of fertility in the four breeds during the period 2007 to 2011. The ranges of the EPD allowed identification of outstanding sires for FERT. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to perform genome (genome wide association studies [GWAS]) and chromosome (CWAS) wide association analyses to identify single nucleotide polymorphisms (SNPs) associated with growth traits in registered Simmental and Simbrah cattle. Methods: The phenotypes were deregressed BLUP EBVs for birth weight, weaning weight direct, weaning weight maternal, and yearling weight. The genotyping was performed with the GGP Bovine 150k chip. After the quality control analysis, 105,129 autosomal SNP from 967 animals (473 Simmental and 494 Simbrah) were used to carry out genotype association tests. The two association analyses were performed per breed and using combined information of the two breeds. The SNP associated with growth traits were mapped to their corresponding genes at 100 kb on either side. Results: A difference in magnitude of posterior probabilities was found across breeds between genome and chromosome wide association analyses. A total of 110, 143, and 302 SNP were associated with GWAS and CWAS for growth traits in the Simmental-, Simbrahand joint -data analyses, respectively. It stands out from the enrichment analysis of the pathways for RNA polymerase (POLR2G, POLR3E) and GABAergic synapse (GABRR1, GABRR3) for Simmental cattle and p53 signaling pathway (BID, SERPINB5) for Simbrah cattle. Conclusion: Only 6,265% of the markers associated with growth traits were found using CWAS and GWAS. The associated markers using the CWAS analysis, which were not associated using the GWAS, represents information that due to the model and priors was not associated with the traits. [ABSTRACT FROM AUTHOR]

The main bovine reproductive biotechnologies are recapitulated herein in five sections, and their historical development and current status are analyzed, including the results generated in Mexico. In the 1970s, estrus synchronization and ovulation induction began; thus, the reproductive cycle started to be controlled with the resources available at that time, based on the knowledge of bovine reproductive physiology. Over the years, hormone therapy evolved as new compounds were discovered, refining methods to standardize the effect and generating new methods for the release of hormones. The most widely used biotechnology in the world, artificial insemination, owes its expansion to advances in semen processing, among which the development of diluents, cryopreservation, semen sexing, and computer-assisted sperm analysis stand out. The embryonic era began with the development of multi-ovulation and methods for collecting, evaluating, transferring, and cryopreserving embryos. The second embryonic era came with the fully in vitro production of embryos from immature eggs and frozen sperm, known as in vitro embryo production. Great research and material resources have been invested in this procedure, rendering it a pillar of genetic improvement and productivity, in combination with two other tools: sexed semen and genomic evaluations. A golden age of in vitro embryo production is on the horizon, with the possibility to produce accurate modifications in the embryo genome, thanks to gene editing technology. [ABSTRACT FROM AUTHOR]

The objective was to estimate the frequency of serum antibodies against infectious bovine rhinotracheitis (IBRV) and bovine viral diarrhea (BVDV) viruses in unvaccinated bulls, as well as the relationship between the presence of antibodies in serum and the presence of these viruses in semen. Antibodies were detected by ELISA, while the presence of the viruses in semen by PCR. Logistic regression analyses were performed with the PROC GENMOD of SAS. The factors were: state, herd nested in state, and genotype of the bull (except for the presence of the viruses in semen). The degree of association between the presence of serum antibodies and the presence of the viruses in semen was measured by the phi (r) correlation. None of the three factors were significant ( P >0.05). For IBRV, the frequency of serum antibodies by state ranged from 66 to 86 %, while by herd, it ranged from 28 to 90 %. For BVDV, the frequency of serum antibodies by state ranged from 58 to 76 %, while by herd, it ranged from 43 to 86 %. The presence of IBRV in semen, by state, ranged from 50 to 55 %, while by herd, it ranged from 33 to 80 %. No association ( P >0.05) was found between the presence of antibodies in serum and the presence of IBRV (r=0.07) and BVDV in semen (r=0.16). The presence of se rum antibodies suggests infection of bulls, but the presence of the viruses in semen suggests their transmission by sexual contact. [ABSTRACT FROM AUTHOR]

The objective was to estimate the frequency of serum antibodies against infectious bovine rhinotracheitis (IBRV) and bovine viral diarrhea (BVDV) viruses in unvaccinated bulls, as well as the relationship between the presence of antibodies in serum and the presence of these viruses in semen. Antibodies were detected by ELISA, while the presence of the viruses in semen by PCR. Logistic regression analyses were performed with the PROC GENMOD of SAS. The factors were: state, herd nested in state, and genotype of the bull (except for the presence of the viruses in semen). The degree of association between the presence of serum antibodies and the presence of the viruses in semen was measured by the phi (r) correlation. None of the three factors were significant ( P >0.05). For IBRV, the frequency of serum antibodies by state ranged from 66 to 86 %, while by herd, it ranged from 28 to 90 %. For BVDV, the frequency of serum antibodies by state ranged from 58 to 76 %, while by herd, it ranged from 43 to 86 %. The prese nce of IBRV in semen, by state, ranged from 50 to 55 %, while by herd, it ranged from 33 to 80 %. No association ( P >0.05) was found between the presence of antibodies in serum and the presence of IBRV (r=0.07) and BVDV in semen (r=0.16). The presence of se rum antibodies suggests infection of bulls, but the presence of the viruses in semen suggests their transmission by sexual contact. [ABSTRACT FROM AUTHOR]

The study analyzed, in two years, the effects of breed [Brahman (BHM; n= 65); Braunvieh (BR; n= 56 )], supplementation with Zilpaterol® (ZIL; treated or control), season of birth (spring or autumn) and their interactions on body surface (BS), age (APB), body weight (WPB), body condition (BC), long dorsal muscle (DM) depth, dorsal fat (DF) thickness and serum leptin concentration (LEP) at puberty (PB) of 121 heifers. At PB, BMHs were heavier and older than BRs (376.8 ± 7.4 vs 302.0 ± 6.6 kg; 588.1 ± 14.7 vs 445.5 ± 12.5 days). ZIL increased APB, WPB, BC and DM, but did not affect DF and LEP. BHMs had 18 % more BS than BRs. However, the difference in WPB/BS was only 6.4 %. When metabolic weight (MW) was used as a proportion of BS (MW/BS) instead of WPB, the difference between BHM and BR disappeared ( P >0.05). The DF was 63.7 % higher in BHM than in BR. Those born in spring started PB with 24.4 % less DF than those born in autumn. Most of the BHM heifers (73.8 %) started PB in the months when light hours were increasing ( P <0.05), while in BRs, the beginning of PB was uniformly distributed throughout the year, regardless of the length of light hours; this effect was present in the two years of study. It is concluded that the establishment of puberty is a multifactorial phenomenon; seasonality affects BHM and BR differently and, apparently, BS is an important fac tor, probably associated with efficiency in energy use. This paper reiterates the importance of dorsal fat and documents, for the first time, MW/BS and its association with the establishment of puberty. [ABSTRACT FROM AUTHOR]

Tick infestation is an ongoing challenge in cattle production, but chemical control methods can pose a risk to both animals and handlers. An evaluation was done of natural Rhipicephalus microplus infestation, its correlation to climatological factors and its effect on weight gain in dual-purpose cattle. Individuals consisted of 31 Bos taurus x Bos indicus cattle of both sexes with an average age of 307 d. Every 28 d for 15 mo, counts of semi-engorged ticks (4.5 to 8.0 mm in diameter) were done and the animals weighed. Tick counts were done from the head to the base of the tail, including the fore and hind limbs, and the ventral region. Response variables were tick count and average weight per animal. Average tick count per animal was higher (P<0.05) in the hottest month (July) than in the other months. Calf's sex and breed group had no effect (P>0.05) on tick count. Individual weight gain decreased 34 g (P<0.05) for each semi-engorged tick per 28-day period. Tick count had a low correlation (P<0.01) with environmental temperature and relative humidity, but average weight gain was negatively and moderately correlated with tick count (-0.67; P<0.01). Animals with a high infestation level (61+ ticks) exhibited lower average weight gain (P=0.001) than those with a medium (31 to 60 ticks) or low level (0 to 30 ticks). Boophilus microplus infestation in dual-purpose cattle requires stricter control during high-temperature months (April to July). [ABSTRACT FROM AUTHOR]

Objective. To determine the prevalence of antibodies against Neospora caninum (PSA) in beef and dual-purpose cattle from the Central and Southern Gulf of Mexico regions, as well as to evaluate its association with the reproductive status (RS) of the cow (pregnant, not pregnant). Materials and methods. Blood samples were taken from 422 cows. Antibodies were detected with a commercial ELISA kit. PSA was analyzed with a logistic regression model that included state, township nested within state, and ranch nested within township. Results. The states of Tabasco, Puebla and Veracruz had similar PSA (p>0.05). The mean PSA for the three states was 24.0%. The PSA varied from 7.8 to 43.3% across townships. In Puebla, the PSA in cattle from San José Acateno township was more than two-fold greater than that in cattle from Hueytamalco and Nauzontla townships (p<0.05). In Tabasco, Cunduacán, Huimanguillo and Ranchería El Puente townships showed similar (p>0.05) PSA. In Veracruz, cows from Cotaxtla and Medellín de Bravo townships presented higher (p<0.05) PSA than those from San Rafael township. The RS of seropositive females was similar (p>0.05) to that of seronegative females. Conclusions. The three states had similar PSA. All the herds had antibodies against N. caninum, suggesting that this parasite is amply distributed in the three states. In addition, great variation existed among herds and among townships; finally, the presence of N. caninum antibodies was not associated with the RS of the cow. [ABSTRACT FROM AUTHOR]

The objective was to evaluate some morphological characteristics of backyard chickens (n=255) coming from 65 rural production units located in 52 municipalities of 18 States of the Mexican Republic. The statistical model included sex, state, and municipality within state. Sex affected all the response variables (P<0.0001), except massiveness index (P=0.3369). State affected all the response variables (P<0.0001) and municipality was only important for wingspan (P<0.0001), body weight (P<0.0271) and stockiness index (P<0.0267). Male chickens had greater (P<0.0001) body length (4.85 cm more), wingspan (5.66 cm more), breast circumference (2.94 cm more), shank length (1.73 cm more), body weight (0.65 kg more) and massiveness index (0.99 percentage points) than female chickens. Body weight increased 126 g (P<0.01) in males and 61 g in females (P<0.01) for each centimeter increment in breast circumference. Body weight showed to be moderately correlated (P<0.01) with body length (r= 0.65), wing span (r= 0.49), length of the shank (r= 0.67) and highly correlated with breast circumference (r= 0.76 in males). The Mexican backyard chicken presented significant morphological differences between males and females for traits studied, except for massiveness index. [ABSTRACT FROM AUTHOR]

Data from 241 interviews collected in 2013 was analyzed to characterize populations of pigs (Mexican Hairless Pig (MH), Cuino Pig (CU) and Crossbred Pig (UD)). Variables were body weight (BW), head length (HL), body length (BL), thoracic perimeter (CG), height at withers (HW), croup width (RW), number of nipples (TC), dense or sparse hair (HD), presence or absence of tusks (TU), short or long snout (ST), upright or floppy ears (ER), calm or restless temperament (TM), proportionality index (PI), body index (BI) and relative weight index (RWI). Analyses were carried out with GLM and GENMOD of SAS. Models included state and population. Population was significant (P<0.05) for BW, BL, CG, HW, RW, TU, TM, PI, BI and RWI. Coefficients of variation (VC) showed the minor and major values for BW (18.8 %) and CG (27.8 %). VC were 13.0, 14.6 and 45.8 % for PI, BI and RWI. Least squares means for MH, CU and UD were: 48.06±6.17a, 35.93±3.04b and 61.11±7.42a kg (BW); 77.81±3.65ab, 69.56±2.02a and 88.52±4.93b cm (BL); 80.55±3.98ab, 71.72±2.20a and 93.23±5.37b cm (CG); 56.88±2.45ab, 51.26±1.36a and 60.32±3.31b cm (HW); 57±4a, 71±19b and 62±34a % (HD); 68±31ab, 70±14a and 61±27b% (TU); 65±30a, 56±12b and 62±3a% (TM). The MH and UD populations were similar in morphometry and different from the CU population. The CU population showed lower weight, smaller size and calmer temperament. The characterization of these populations is important for designing strategies for their conservation and efficient use. [ABSTRACT FROM AUTHOR]

The objective of the present study was to estimate (co)variance components, heritabilities and genetic and phenotypic correlations for yearling weight (YW), scrotal circumference (SC) and frame score (FS) of Simmental and Simbrah young bulls from Mexico. All traits were adjusted to 365 d according to the Beef Improvement Federation (BIF). Final data file included 1,949 Simmental and 1,259 Simbrah records. A three-trait animal model was used to estimate (co)variance components and genetic parameters. For each trait, the model included fixed effects of herd-year-season, and the age of dam, gene proportion of Simmental breed, heterozygosity and recombination losses effects as covariates; animal and residual were included as random effects. Additive variances were 376.3±130.9 kg2, 2.89±0.69 cm2 and 0.37±0.08 units2; and heritabilities were 0.33±0.11, 0.35±0.08 y 0.42±0.08, for YW, SC and FS, respectively. Genetic correlations were 0.36±0.19, 0.47±0.17 and 0.59±0.12, for YW-SC, YW-FS and SC-FS, respectively. Heritability estimates show that a favorable response would exist to selection for the studied traits. Genetic correlations indicate that no genetic antagonisms exist, suggesting that would be a positive correlated response to selection of any trait. It would be necessary the use of selection indices in order to avoid greater FS as correlated response due to direct selection of YW and SC. [ABSTRACT FROM AUTHOR]

El objetivo fue estimar los componentes de (co)varianza, heredabilidades y correlaciones genéticas y fenotípicas para peso al año (YW), circunferencia escrotal (SC) y talla (FS) en toros jóvenes Simmental y Simbrah de México. Todas las características se ajustaron a 305 días acorde a los lineamientos descritos por la Federación para el Mejoramiento Genético de los Bovinos de Carne (BIF). El archivo final de datos incluyó 1,949 registros Simmental y 1,259 Simbrah. Para estimar los compones de (co)varianza y parámetros genéticos se usó un modelo animal de tres características. Para cada característica, el modelo incluyó los efectos fijos de hato-año-estación; como covariables se incluyeron la edad de la madre, proporción de genes de raza Simmental, heterocigosis y los efectos por pérdida de recombinación; los efectos de animal y residual se incluyeron como aleatorios. Las varianzas genéticas aditivas fueron 376.3±130.9 kg2, 2.89±0.69 cm2 y 0.37±0.08 unidades2; y las heredabilidades fueron 0.33±0.11, 0.35±0.08 y 0.42±0.08, para YW, SC y FS, respectivamente. Las correlaciones genéticas fueron 0.36±0.19, 0.47±0.17 y 0.59±0.12 para YW-SC, YW-FS, y SC-FS, respectivamente. Las estimaciones de heredabilidad muestran que puede existir una respuesta favorable en la selección para las características estudiadas. Las correlaciones genéticas indican que no existen antagonismos genéticos, sugiriendo que habría una respuesta correlacionada positiva en la selección de cualquiera de ellas. [ABSTRACT FROM AUTHOR]

Data were collected between 2001 and 2003 from Guzerat (G), Criollo (C), Criollo*Guzerat (CG) and Guzerat*Criollo (GC) cows (n=619 records). Variables analyzed were fat (G%), protein (P%), lactose (L%), non fat solids (SNG%) content in milk expressed as percentages, and total fat (GP), protein (PP), lactose (LP) and non fat solids (SNGP) expressed in kg produced in each lactation. Birth (PN) and 210-d weaning weight (PA210), were analyzed too. Heterosis, direct and maternal genetic effects were estimated as well as the relationship between milk components and PA210. For G%, P%, L%, SNG%, GP, PP, LP and SNGP, models included fixed effects of cow genetic group (GEN), year of calving (A), calving number (NP), postpartum days (D), calving season (E) and two factors interactions (F). For PN and PA210 models included GEN, NP, E, A and F. Residual correlations between PA210 and milk components were estimated. Heterosis was significant (P<0.05) for GP (5.07±1.9 kg), PP (4.97±1.5 kg), LP (7.04±2.1), SNGP (13.48±3.8 kg), PN (-1.3±0.6 kg) and PA210 (12.65±4.2 kg). Direct genetic effects were positive to G (P<0.05) for LP (11.08±3.7 kg), SNGP (16.98±6.6 kg), PN (3.80±1.1 kg) and PA210 (37.60±7.6 kg). Significant correlations (P<0.05) were found between PA210 and GP (016), LP (0.21) and SNGP (0.19). Correlations suggest that quantity of milk components was important to determine weaning weight of calves. [ABSTRACT FROM AUTHOR]

Se utilizaron 619 registros productivos generados entre 2001 y 2003 por vacas Guzerat (G), Criollo (C), Guzerat x Criollo (GC) y Criollo x Guzerat (CG). Las variables estudiadas fueron porcentaje de grasa (%G), proteína (%P), lactosa (%L) y sólidos no grasos (%SNG) contenidos en la leche y kilogramos de grasa (GP), proteína (PP), lactosa (LP) y sólidos no grasos (SNGP) producidos por lactancia. También se evaluaron peso al nacer (PN) y peso al destete ajustado a 210 días de edad (PA210) y se estimaron efectos genéticos directos, maternos, de heterosis y la relación entre componentes de la leche y PA210. Para %G, %P, %L, %SNG, GP, PP, LP y SNGP los modelos incluyeron los efectos fijos de grupo genético de la vaca (GEN), número de parto (NP), año de parto (A), época de parto (E), días posparto (D) e interacciones de dos factores (F). Para PN y PA210 los modelos incluyeron GEN, NP, A, E y F. Se estimaron correlaciones residuales entre componentes de la leche y PA210. Heterosis fue importante (P<0.05) para GP (5.07±1.9 kg), PP (4.97±1.5 kg), LP (7.04±2.1 kg), SNGP (13.48±3.8 kg), PN (-1.30±0.6 kg) y PA210 (12.65±4.2 kg). Los efectos genéticos directos para LP, SNGP, PN y PA210 fueron favorables (P<0.05) a G en 11.08±3.7, 16.98±6.6, 3.80±1.1 y 37.60±7.6 kg. Se detectaron correlaciones importantes (P<0.05) de PA210 con GP (0.16), LP (0.21) y SNGP (0.19). Las correlaciones sugieren que la cantidad de componentes en la leche fue importante para determinar el peso al destete de los becerros. [ABSTRACT FROM AUTHOR]