Search

Records on 514 bulls from the sire population born from 1978 to 2004, and on 22,099 of their field progeny born from 1997 to 2003 with available pedigree information (total number = 124,458) were used to estimate genetic parameters for feed intake and energy efficiency traits of bulls and their relationships with carcass traits of field progeny. Feed intake and energetic efficiency traits were daily feed intake, TDN intake, feed conversion ratio (FCR), TDN conversion ratio (TDNCR), residual feed intake (RFI), partial efficiency of growth, relative growth rate, and Kleiber ratio. Progeny carcass traits were carcass weight (CWT), yield estimate, ribeye area, rib thickness, subcutaneous fat thickness (SFT), marbling score (MSR), meat color standard (MCS), fat color standard (FCS), and meat quality grade. All measures of feed intake and energetic efficiency were moderately heritable (ranged from 0.24 to 0.49), except for partial efficiency of growth and relative growth rate, which were high (0.58) and low (0.14), respectively. The phenotypic and genetic correlations between FCR and TDNCR were [greater than or equal to] 0.93. Selection for Kleiber ratio will improve all of the energetic efficiency traits with no effect on feed intake measures (daily feed intake and TDN intake). The genetic correlations of FCR, TDNCR, and RFI of bulls with most of the carcass traits of their field progeny were favorable (ranged from -0.24 to -0.72), except with fat color standard (no correlation), MCS, and SFT. Positive (unfavorable) genetic correlations of MCS with FCR, TDNCR, and RFI (0.79, 0.70, and 0.51, respectively) were found. The SFT was negatively genetically correlated with FCR and TDNCR (-0.32 and -0.20, respectively); however, the genetic correlation between RFI and SFT was not significantly different from zero ([r.sub.g] = -0.08 [+ or -] 0.12). Favorable correlated responses in CWT, yield estimate, ribeye area, rib thickness, MSR, and meat quality grade would be predicted for selection against any measure of energetic efficiency. The correlated responses in CWT and MSR of progeny were greater for selection against RFI than for selection against any other energetic efficiency trait. Results of this study indicate that RFI should be preferred over other measures of energetic efficiency to include in selection programs. Key words: beef cattle, carcass trait, feed efficiency, genetics

Economic benefits from the use of expected progeny of a sample of beef bulls with genetic evaluations were calculated over an integrated supply chain for combinations of price discounts for intramuscular fat and LM area. Fixed backfat finish and marketing at the point of optimized gross margins were considered. An economic model was used to calculate average expected gross margins for a sample of bulls. Across-breed, age-constant genetic evaluations were used to predict carcass characteristics of progeny including weight, retail yield, intramuscular fat, and LM area, as well as input requirements including feed and housing as a function of time on feed. Proportion of retail cuts affected by price discounts was included in the calculations. Optimizing endpoints did not affect rankings to any extent relative to a fixed end point in this sample of bulls, as a result of fixed endpoints being similar to optimized endpoints for the economic situation considered. However, rank correlations were only 0.63 and 0.71 between rankings for no discount being applied and rankings with discounts for intramuscular fat and LM area, for fixed and optimized endpoints, respectively. We conclude that market prices are necessary considerations in choices of bulls to use in commercial beef production. Key words: beef production, bioeconomic model, genetic evaluation, sire ranking

We constructed a metric linkage disequilibrium (LD) map of bovine chromosome 6 (BTA6) on the basis of data from 220 SNPs genotyped on 433 Australian dairy bulls. This metric LD map has distances in LD units (LDUs) that are analogous to centimorgans in linkage maps. The LD map of BTA6 has a total length of 8.9 LDUs. Within the LD map, regions of high LD (represented as blocks) and regions of low LD (steps) are observed, when plotted against the integrated map in kilobases. At the most stringent block definition, namely a set of loci with zero LDU increase over the span of these markers, BTA6 comprises 40 blocks, accounting for 41% of the chromosome. At a slightly lower stringency of block definition (a set of loci covering a maximum of 0.2 LDUs on the LD map), up to 81% of BTA6 is spanned by 46 blocks and with 13 steps that are likely to reflect recombination hot spots. The mean swept radius (the distance over which LD is likely to be useful for mapping) is 13.3 Mb, confirming extensive LD in Holstein--Friesian dairy cattle, which makes such populations ideal for whole-genome association studies.

The objective of this study was to determine the effect of carprofen (C) administration before banding or burdizzo castration of bulls on cortisol, in vitro interferon-[gamma] (IFN-[gamma]) production, acute-phase proteins, feed intake, and growth. Fifty Holstein Friesian bulls (5.5 mo old; 191 [+ or -] 3.7 kg) were blocked by weight and assigned randomly to 1 of 5 treatments (n = 10/ treatment): 1) untreated control (2) banding castration at 0 min (Band); 3) Band following an i.v. injection of 1.4 mg/kg of BW of C at -20 min (Band+C); 4) Burdizzo castration at 0 min (Burd); or 5) Burd following 1.4 mg/ kg of BW of C at -20 min (Burd+C). Castration acutely increased plasma cortisol concentrations compared with control; no significant differences occurred in peak and interval to peak cortisol responses between Band and Band+C or Burd and Burd+C groups. The administration of C in Band+C reduced (P < 0.05) the cortisol concentration between 6 and 12 h postcastration compared with Band animals. Overall, the integrated cortisol response was greater (P < 0.05) in the castrates than in control, whereas C treatments tended to reduce this response compared with Band (P = 0.08) and Burd (P = 0.07), respectively. Plasma fibrinogen was elevated in Band animals on d 14 and in Burd animals on d 3 and 14. Carprofen administration reduced Band- and Burd-induced fibrinogen production on d 14 and 3, respectively. Plasma haptoglobin was elevated in Band animals on d 3 and 35 compared with control, and C adminstration was effective in reducing the haptoglobin elevation on d 35 in Band+C compared with Band. There were no differences among treatments in in vitro IFN-[gamma], production induced by concanavalin A and phytohemagglutinin on d 1 and 2. Overall from d-1 to 16, there were no DMI differences among treatments. From d-1 to 35, there were no ADG differences among treatments. In conclusion, banding and burdizzo castration increased plasma cortisol with no change in in vitro IFN-[gamma] production. Carprofen (1.4 mg/kg of BW) tended to reduce the integrated cortisol response, and it reduced cortisol secretion in banded animals between 6 and 12 h postcastration. There was an increased acute-phase protein production following castration; this response was effectively moderated by the administration of C before castration. Key words: acute-phase protein, carprofen, castration, cattle, interferon-[gamma], stress

The objective of this study was to evaluate the influence of bull excretory products on the resumption of postpartum luteal function in primiparous, restricted-suckled cows. Hypotheses tested were that resumption of luteal function or proportions of cows that initiate luteal cycling did not differ among cows exposed to a bull (BE), exposed to excretory products of bulls (EPB), not exposed to a bull (NE), or exposed to excretory products of cows (EPC). Two-year-old Angus x Hereford cows were assigned 35 d after calving to one of the four treatments (n = 15, 16, 16, and 15 for BE, EPB, NE, and EPC, respectively). Cows in the EPB and EPC treatments were placed in enclosures for 10 to 12 h, between 1830 and 0800 daily. Each enclosure was occupied by bulls (EPB) or left empty (EPC) for 10 to 12 h (0800 to 1830) daily. All cows were restricted to suckling twice daily (0800 and 1800) beginning on d 0. Blood samples were obtained from each cow on d -1 and every third day of the study thereafter. An increase in progesterone concentrations in three consecutive samples that exceeded 1.0 ng/mL was used as evidence of resumption of luteal function. Interval from d 0 to resumption of luteal activity was less for (P < 0.05) BE and EPB cows than for NE cows, but did not differ between BE and EPB cows. Interval for EPC cows did not differ from that for NE cows; however, interval for EPC cows was greater (P = 0.06) than that for BE cows and was longer (P < 0.05) than that of EPB cows. Proportions of cows that resumed luteal function by d 40 and 50 did not differ between NE and EPC cows; however, proportions of EPB and BE cows that resumed luteal function were greater (P < 0.05) than those for NE and EPC cows by d 40 and 50. Proportions of cows that resumed luteal function by d 70 were greater (P < 0.05) for BE, EPB, and EPC cows than for NE cows; however, proportions of BE and EPC cows did not differ. The proportion of EPB cows that resumed luteal function was greater (P = 0.058) than that of EPC cows, but the proportion of BE cows that resumed luteal function did not differ from that of EPC cows by d 70. We conclude that exposing primiparous restricted-suckled cows to excretory products of bulls or crowding estrus-cycling cows in an enclosure hastened postpartum resumption of luteal function. Therefore, the biostimulatory role of bulls and the crowding effect of cows seem to be mediated by a pheromone (or pheremones) present in their excretory products. Key Words: Biostimulation, Bovine, Bulls, Pheromone, Postpartum Interval

The objective of this study was to estimate parameters required for genetic evaluation of Simmental carcass merit using carcass and live animal data. Carcass weight, fat thickness, longissimus muscle area, and marbling score were available from 5,750 steers and 1,504 heifers sired by Simmental bulls. Additionally, yearling ultrasound measurements of fat thickness, longissimus muscle area, and estimated percentage of intramuscular fat were available on Simmental bulls (n = 3,409) and heifers (n = 1,503). An extended pedigree was used to construct the relationship matrix (n = 23,968) linking bulls and heifers with ultrasound data to steers and heifers with carcass data. All data were obtained from the American Simmental Association. No animal had both ultrasound and carcass data. Using an animal model and treating corresponding ultrasound and carcass traits separately, genetic parameters were estimated using restricted maximum likelihood. Heritability estimates for carcass traits were 0.48 [+ or -] 0.06, 0.35 [+ or -] 0.05, 0.46 [+ or -] 0.05, and 0.54 [+ or -] 0.05 for carcass weight, fat thickness, longissimus muscle area, and marbling score, respectively. Heritability estimates for bull (heifer) ultrasound traits were 0.53 [+ or -] 0.07 (0.69 [+ or -] 0.09), 0.37 [+ or -] 0.06 (0.51 [+ or -] 0.09), and 0.47 [+ or -] 0.06 (0.52 [+ or -] 0.09) for fat thickness, longissimus muscle area, and intramuscular fat percentage, respectively. Heritability of weight at scan was 0.47 [+ or -] 0.05. Using a bivariate weight model including scan weight of bulls and heifers with carcass weight of slaughter animals, a genetic correlation of 0.77 [+ or -] 0.10 was obtained. Models for fat thickness, longissimus muscle area, and marbling score were each trivariate, including ultrasound measurements on yearling bulls and heifers, and corresponding carcass traits of slaughter animals. Genetic correlations of carcass fat thickness with bull and heifer ultrasound fat were 0.79 [+ or -] 0.13 and 0.83 [+ or -] 0.12, respectively. Genetic correlations of carcass longissimus muscle area with bull and heifer ultrasound longissimus muscle area were 0.80 [+ or -] 0.11 and 0.54 [+ or -] 0.12, respectively. Genetic correlations of carcass marbling score with bull and heifer ultrasound intramuscular fat percentage were 0.74 [+ or -] 0.11 and 0.69 [+ or -] 0.13, respectively. These results provide the parameter estimates necessary for genetic evaluation of Simmental carcass merit using both data from steer and heifer carcasses, and their ultrasound indicators on yearling bulls and heifers. Key Words: Beef Cattle, Carcasses, Genetic Parameters, Simmental, Ultrasound

The objective of this study was to estimate genetic parameters for real-time ultrasound measurements of longissimus muscle area (LMA), 12th rib backfat thickness (FT), percent intramuscular fat (IMF), and yearling weight (YW) for 1,299 yearling Brangus bulls and heifers. A single ultrasound technician performed all measurements. The number of observations was 1,298, 1,298, 1,215, and 1,170 for LMA, FT, IMF, and YW, respectively. Genetic parameters were estimated for each trait using single- and multiple-trait derivative-free restricted maximal likelihood. Fixed effects were contemporary group (defined as same sex, same age within six months, and same environment), and days of age as a covariate. Correlations were estimated from two-trait models. Heritabilities for LMA, FT, IMF, and YW were 0.31, 0.26, 0.16, and 0.53, respectively. Genetic correlations between LMA and FT, LMA and IMF, LMA and YW, FT and IMF, FT and YW, and IMF and YW were 0.09, 0.25, 0.44, 0.36, 0.42, and 0.31, respectively. Yearling live animal ultrasonic measurements can be used as a selection tool in breeding cattle for the improvement of carcass traits. Key Words: Genetic Correlation, Genetic Parameters, Heritability, Ultrasound

The aim of this study was to evaluate the effect of including concomitant body weight and(or) a random dam effect in genetic evaluation models on variance component estimates and standard error of prediction for scrotal circumference (SC) at 6, 8, 10, and 12 mo. Variance components and average standard errors of prediction were compared under models differing in either the number of related traits (M11 [SC], M12 [SC and BW]) or an uncorrelated random dam effect (M21 [SC], M22 [SC and BW]) using records on 1,547 bull calves. In a single-trait model (M11), estimates of direct heritabilities (mathematical expression not reproducible in ASCII) for SC were .45, .49, .57, and .66 at 6, 8, 10, and 12 mo, respectively. In a two-trait model (M12), (mathematical expression not reproducible in ASCII) were similar to those in M11 model. In M21, (mathematical expression not reproducible in ASCII) for SC were .37, .42, .54, and .65, whereas the proportions of phenotypic variance due to dams (mathematical expression not reproducible in ASCII) were .12, .11, .04, and .02 at 6, 8, 10, and 12 mo, respectively. Similarly, in M22, (mathematical expression not reproducible in ASCII) for SC were .36, .44, .56, and .65 and (mathematical expression not reproducible in ASCII) were .13, .10, .02, and .02. Standard errors of prediction for SC EBV from M22 were reduced by 2.86, 1.21, 3.02, and 1.99% relative to M21 and by 6.45, 2.70, 2.72, and 1.21% relative to M11 at 6, 8, 10, and 12 mo, respectively. Standard errors of prediction for SC EBV from M12 were reduced by .06, .73, 1.56, and .87% relative to M11 at 6, 8, 10, and 12 mo, respectively. The importance of the dam effect decreased with age for both SC and BW. These results demonstrate that a two-trait (SC and BW) animal model would result in more accurate evaluations of yearling SC EBV in beef cattle than a single-trait model. Key Words: Beef Cattle, Scrotum, Variance Components

Breeding soundness examination data from 1,282 registered Angus bulls in four herds were used to estimate genetic parameters of breeding soundness traits, presence of seminal white blood cells, and common penile defects. Average age of the bulls at the time of evaluation was 383 days. Data were analyzed using single- and two-trait animal models and a derivative-free REML algorithm. Estimates of heritability for scrotal circumference (SC), percent motility, percent primary abnormalities, percent secondary abnormalities and percent total abnormalities were .56, 07, .35, .26 and .29, respectively. Estimates of heritability for the presence of seminal white blood cells, persistent penile frenulum, and penile fibropapillomatosis (warts) on the underlying normal scale were .02, .00, and .004, respectively. Genetic correlations between SC and semen quality parameters were low to moderate and favorable. Phenotypic correlations between SC and semen quality estimates were low and favorable. These results indicate that SC is the most heritable of breeding soundness components and that no undesirable responses in semen quality traits can be expected as a result of selection for increased SC. Conditions such as seminal vesiculitis, persistent penile frenulum, and penile fibropapillomatosis are of low heritability, and if corrected through management or treatment, should not be selected against by producers. Key Words: genetic parameters, scrotum, semen characters