Meat Animal Research Center Research Articles

Increased calf production in cattle selected for twin ovulations1,2

The effects of increasing fetal numbers and their distribution between the left and right uterine horns on calf survival, calf BW at birth and weaning, gestation length, dystocia, and calf sex ratio were evaluated for single (n = 1,587), twin (n = 2,440), and triplet calves (n = 147) born to primiparous and multiparous females in the Twinner population at the US Meat Animal Research Center between 1994 and 2004. Cattle were distributed equally between the spring and fall breeding seasons. Fetal number and distribution in utero were determined by real-time ultrasonography at 40 to 70 d postbreeding. For cows and heifers combined, number of calves per parturition increased from 1.34 in 1994 to 1.56 in 2004. Gestation length was 6.8 d shorter (P < 0.01) for twins compared with singles (277.5 +/- 0.2 vs. 284.3 +/- 0.2 d) and 12.7 d shorter for triplets (271.6 +/- 0.8 d). Survival and BW of individual calves at birth decreased (P < 0.01) but total calf BW per dam increased (P < 0.01) as fetal number increased from single to triplet births. Twins resulting from bilateral twin ovulations had increased (P < 0.01) survival and BW at birth, a longer (P < 0.01) gestation length, and less (P < 0.01) dystocia than twins resulting from unilateral twin ovulations. Calf survival and BW at birth were 97.2 +/- 0.3% and 48.0 +/- 0.1 kg for singles, 92.0 +/- 0.4% and 39.0 +/- 0.2 kg for bilateral twins, 83.2 +/- 0.4% and 36.7 +/- 0.2 kg for unilateral twins, 73.8 +/- 1.4% and 30.6 +/- 0.7 kg for bilateral triplets, and 51.9 +/- 3.2% and 31.7 +/- 1.6 kg for unilateral triplets. Birth weight of single calves increased by 0.51 kg/d for each additional day of gestation length vs. 0.38 kg/d for individual twins. Calf BW at birth increased (P < 0.01) with age of dam from 2 to 4 yr. Twin and triplet births had a greater (P < 0.01) incidence of dystocia than single births. The ratio of male:female calves (0.52:0.48) at birth was not affected by type of birth. Postnatal calf survival was similar for all 3 types of birth. Total progeny BW at weaning for single, twin, and triplet births was 217.7 +/- 2.5, 328.3 +/- 3.2, and 378.4 +/- 15.0 kg, respectively (P < 0.01). Although most bovine females have the uterine capacity to gestate twin calves, decreased survival and BW of unilateral twins and of all triplets indicate that their growth and development may have been compromised by uterine crowding.

Across-breed adjustment factors for expected progeny differences for carcass traits1

Adjustment factors to allow comparison of EPD from several breed associations for birth, weaning, and yearling weights have been available for more than 10 yr. This paper describes steps to calculate adjustment factors for EPD for 4 carcass traits: marbling score, fat thickness, ribeye area, and retail product percentage. The required information is the same as for the weight traits: 1) breed of sire solutions based on measurements on progeny at the US Meat Animal Research Center (USMARC) that have sires with breed association EPD, 2) mean EPD of sires weighted by number of progeny at USMARC (USMARC progeny not included in breed association EPD), and 3) mean EPD of nonparents from breed associations (defined as animals born 2 yr prior to calculation of EPD). Records at USM-ARC are adjusted to 100% heterozygosity because the purpose of the adjustment factors is to allow prediction of performance of progeny of sires mated to other breeds of dam. A critical step is to adjust breed of sire solutions, which are based on an earlier sample of sires, to the equivalent of a sample from a more recent nonparent group using the difference between mean EPD from information sources 2) and 3). The difference is multiplied by the coefficient of regression of USMARC progeny on EPD of their sires. With weight traits, these coefficients are not greatly different from unity. With the carcass traits, 2 sets of coefficients can be used depending on whether the EPD are based on carcass or ultrasound measurements. The regression coefficients also reflect differences in conditions for USMARC progeny (all steers) and factors associated with breed association EPD. Only for marbling score and ribeye area were any estimates of the regression coefficients near unity. For other traits, the coefficients ranged from 1.65 to 2.82. The solutions for breed of sire, differences in mean EPD, and regression coefficients are then used to calculate adjustment factors for EPD of 11 breeds including the arbitrary base breed, Angus.

Effects of a Single Foot Rot Incident on Weight Performance of Feedlot Steers

AbstractFeedlot performance records from the U.S. Meat Animal Research Center feedlot for 1993 through 2000 were analyzed to evaluate the impact of foot rot on ADG and total days on feed. Records from the original pool of 36,755 bull, steer, and heifer calves were sorted so that only steers that had a single foot rot incidence and no other morbidities were included in the data set (7,100 steers). To roughly pattern these data to industry production practices, time of foot rot insult during feeding was divided into 3 production periods: starting (0 to 60 d), growing (61 to 120 d), and finishing (121 d to harvest). Records were evaluated to determine which limb was more likely to be affected with foot rot. A total of 459 (6.5%) steers were treated for a single foot rot incident. The ADG for cattle not affected by foot rot was 1.30kg. For cattle experiencing a single foot rot incident, the ADG was 1.27kg (P = 0.03). The production period of foot rot onset impacted both ADG and total days on feed. Steers diagnosed with foot rot during the starting period gained 0.032 kg/d more (P = 0.083) than non-affected steers. Steers diagnosed in the growing and finishing periods gained 0.009 and 0.049 kg/d less than non-affected cattle (P = 0.438 and P < 0.01, respectively). Mean days on feed for the non-affected cattle was 262 d and mean days on feed for foot rot-affected cattle was 267 d (P < 0.01). The impact of foot rot on days on feed for periods 1 through 3 was −9.9 d, +2.2 d, and +14.3 d (P < 0.01, P = 0.26, P < 0.01, respectively). Foot rot diagnosed in either front limb reduced (P = 0.014) BW gain by 0.031kg.

Association of a single nucleotide polymorphism in SPP1 with growth traits and twinning in a cattle population selected for twinning rate1,2

Continued validation of genetic markers for economically important traits is crucial to establishing marker-assisted selection as a tool in the cattle industry. The objective of the current study was to evaluate the association of a SNP (T(9)/T(10)) in the osteopontin gene (SPP1) with growth rate in a large cattle population spanning multiple generations and representing alleles from 12 founding breeds. This population has been maintained at the US Meat Animal Research Center since 1981 and subjected to selection for twinning rate. Phenotypic records for this population included twinning rate and ovulation rate, providing an opportunity to examine the potential effects of SPP1 genotype on reproductive traits. A set of 2,701 animals was geno-typed for the T(9)/T(10) polymorphism at SPP1. The geno-typic data, including previously genotyped markers on chromosome 6 (BTA6), were used in conjunction with pedigree information to estimate genotypic probabilities for all 14,714 animals with phenotypic records. The genotypic probabilities for females were used to calculate independent variables for regressions of additive, dominance, and imprinting effects. Genotypic regressions were fit as fixed effects in a mixed model analysis, in which each trait was analyzed in a 2-trait model where single births were treated as a separate trait from twin births. The association of the SPP1 marker with birth weight (P < 0.006), weaning weight (P < 0.007), and yearling weight (P < 0.003) was consistent with the previously reported effects of SPP1 genotype on yearling weight. Our data supports the conclusion that the SNP successfully tracks functional alleles affecting growth in cattle. The previously undetected effect of the SNP on birth and weaning weight suggests this particular SPP1 marker may explain a portion of the phenotypic variance explained by QTL for birth and HCW on BTA6.

Comparing Genetic Value of Bulls from Different Breeds: Across Breed EPDs

AN162, a 5-page fact sheet by Gary R. Hansen, describes how to use tables developed by the US Meat Animal Research Center (MARC) which provide adjustment factors to allow for the calculation of across-breed expected progeny differences (AB-EPDs) to assess genetic potential across different breeds. Published by the UF Department of Animal Science, March 2006.

Effects of age, weight, and fat slaughter end points on estimates of breed and retained heterosis effects for carcass traits

The influence of different levels of adjusted fat thickness (AFT) and HCW slaughter end points (covariates) on estimates of breed and retained heterosis effects was studied for 14 carcass traits from serially slaughtered purebred and composite steers from the US Meat Animal Research Center (MARC). Contrasts among breed solutions were estimated at 0.7, 1.1, and 1.5 cm of AFT, and at 295.1, 340.5, and 385.9 kg of HCW. For constant slaughter age, contrasts were adjusted to the overall mean (432.5 d). Breed effects for Red Poll, Hereford, Limousin, Braunvieh, Pinzgauer, Gelbvieh, Simmental, Charolais, MARC I, MARC II, and MARC III were estimated as deviations from Angus. In addition, purebreds were pooled into 3 groups based on lean-to-fat ratio, and then differences were estimated among groups. Retention of combined individual and maternal heterosis was estimated for each composite. Mean retained heterosis for the 3 composites also was estimated. Breed rankings and expression of heterosis varied within and among end points. For example, Charolais had greater (P < 0.05) dressing percentages than Angus at the 2 largest levels of AFT and smaller (P < 0.01) percentages at the 2 largest levels of HCW, whereas the 2 breeds did not differ (P > or = 0.05) at a constant age. The MARC III composite produced 9.7 kg more (P < 0.01) fat than Angus at AFT of 0.7 cm, but 7.9 kg less (P < 0.05) at AFT of 1.5 cm. For MARC III, the estimate of retained heterosis for HCW was significant (P < 0.05) at the lowest level of AFT, but at the intermediate and greatest levels estimates were nil. The pattern was the same for MARC I and MARC III for LM area. Adjustment for age resulted in near zero estimates of retained heterosis for AFT, and similarly, adjustment for HCW resulted in nil estimates of retained heterosis for LM area. For actual retail product as a percentage of HCW, the estimate of retained heterosis for MARC III was negative (-1.27%; P < 0.05) at 0.7 cm but was significantly positive (2.55%; P < 0.05) at 1.5 cm of AFT. Furthermore, for MARC III, estimates of heterosis for some traits (fat as a percentage of HCW as another example) also doubled in magnitude depending on different levels of AFT end point. Rational exploitation of breeds requires special attention to use of different end points and levels of those end points, mainly for fat thickness.

Methods for Recovering Escherichia coli O157:H7 from Cattle Fecal, Hide, and Carcass Samples: Sensitivity and Improvements

The Meats Research Unit (MRU) methods, developed by MRU scientists of the U.S. Meat Animal Research Center, have been used to study the prevalence of Escherichia coli O157:H7 in cattle carcass, hide, and fecal samples. The sensitivity of these methods for recovery of injured E. coli O157:H7 cells from inoculated and uninoculated samples was determined, and potential improvements to these methods were evaluated. When using the conventional MRU methods, 91% of the pre-evisceration carcass samples tested positive for E. coli O157:H7 when inoculated with 5 to 10 CFU, 100% of hide samples tested positive for E. coli O157:H7 when inoculated with 30 to 50 CFU, and 96% of the fecal samples produced positive results when inoculated with 300 to 400 CFU per 10 g. The addition of a phosphate buffer to the tryptic soy broth enrichment improved recovery of E. coli O157:H7 from feces. Using the modified enrichment, 92% of the samples were identified as positive when inoculated with 10 to 30 CFU per 10 g. Substituting a commercially available wash buffer for the phosphate-buffered saline (PBS) plus Tween 20 wash buffer during immunomagnetic separation of hide samples improved recovery of the target organism at lower inoculum concentrations. When comparing uninoculated samples, substituting a PBS buffer plus a zwitterionic detergent for PBS plus Tween 20 also had a positive effect on recovery of E. coli O157:H7 from hide samples. Data presented here indicate that the MRU methods are highly effective at recovering injured E. coli O157:H7 from fecal, hide, and beef carcass samples; however, modifications can be added to increase the sensitivity.

Identification of genetic markers for fat deposition and meat tenderness on bovine chromosome 5: Development of a low-density single nucleotide polymorphism map1,2

As genetic markers, SNP are well suited for the development of genetic tests for production traits in livestock. They are stable through many generations and can provide direct assessment of individual animal's genetic merit if they are in linkage disequilibrium and phase with functional genetic variation. Bovine chromosome 5 has been shown to harbor genetic variation affecting production traits in multiple cattle populations; thus, this chromosome was targeted for SNP-based marker development and subsequent association analysis with carcass and growth phenotypes. Discovery of SNP was performed in a panel of 16 sires representing two sires from each of seven beef breeds and two Holstein sires by PCR amplification and sequencing using primers designed from genomic sequence obtained by low-coverage sequencing of bacterial artificial chromosome (BAC) clones. From 550 SNP, 296 (54%) were tentatively identified as having a minor allele frequency >10%. Forty-five SNP derived from 15 BAC were chosen based on minor allele frequency and were genotyped in 564 steers and their sires. Production and carcass data were collected on the steers as a part of the Germplasm Evaluation (GPE), Cycle VII Project at the U.S. Meat Animal Research Center (Clay Center, NE), which involves of the evaluation of sires from seven of the most popular U.S. breeds. Haplotypes based on seven SNP derived from a BAC containing the bovine genes HEM1 and PDE1B were associated with traits related to carcass fat. Steers homozygous for the major haplotype had 0.15 +/- 0.04 cm less subcutaneous fat, 0.57 +/- 0.18 kg less rib fat, 0.18 +/- 0.07 lower yield grade, 1.11 +/- 0.35% less predicted fat yield, and 0.79 +/- 0.3% greater predicted retail product yield than heterozygotes. The frequency of the major haplotype was 0.70 in the steers, and it ranged from 0.44 (Limousin) to 0.98 (Simmental and Gelbvieh) in a panel consisting of an average of 20 purebred sires from each of the seven breeds. A second set of haplotypes based on four SNP derived from a BAC containing the genes NOL1 and CHD4 was associated with Warner-Bratzler shear force. Steers homozygous for the major haplotype had 0.27 +/- 0.11 kg greater shear force than those heterozygous for the major haplotype and one of two minor haplotypes. The frequency of the major haplotype was 0.59 in the steers and ranged from 0.27 (Hereford) to approximately 0.95 (Angus and Red Angus) in the panel of purebred sires. These results demonstrate the feasibility of targeting QTL regions for SNP-based marker development and that a low level of coverage can identify markers associated with phenotypic traits.

Genetic Relationships Between Male and Female Reproductive Traits in Beef Cattle

AbstractReproductive traits were measured for 234 bulls and 1184 heifers from matings of three dam breeds (Angus, Hereford, and MARC III) with six sire breeds (Angus, Hereford, Brahman, Boran, Tuli, and Belgian Blue) from the Germ Plasm Evaluation (GPE) Program at Roman L. Hruska US Meat Animal Research Center. Male traits were yearling scrotal circumference (YSC), height (YH), and yearling BW; age at puberty (API; production of 50 million sperm with ≥10% progressive motility); age, scrotal circumference, average testis length, and testicular volume when 500 million sperm were produced with ≥50% progressive motility (AP3, SC3, L3 and V3, respectively); and 15-mo BW (15W) and height (15H). Traits of females were age at puberty (AP, first estrus) and pregnancy rate (PR) at 18 mo. The objective was to determine whether indirect selection on male traits would be effective for improving female fertility traits. Selection of males on AP1, AP3, SC3, L3, V3, YH, 15W, and 15H may be useful for improving PR because of genetic correlations and low heritability for PR. Although no male trait was found to be effective for improving AP in females through indirect selection, YSC and SC3 were the most favorable. If heritability were as large as estimated in this study for AP (0.52), direct rather than indirect selection would seem to be more effective for AP in heifers, although the difficulty of measuring AP in heifers also would need to be considered. Male reproductive traits, such as scrotal circumference and also YH and 15H, however, are easier and less expensive to measure than female reproductive traits, and greater selection intensity can be applied to these male traits.

Linkage and RH mapping of the porcine adiponectin gene on chromosome 13

USDA ARS, US Meat AnimalResearch Center, Spur 18D, PO Box 166, Clay Center, NE 68933-0166, USAAccepted for publication 17 March 2005Source/description: A fragment of the porcine adipocyte, C1Qand collagen domain containing (ADIPOQ) gene, whichencodes adiponectin, was amplified using primer pair A(Table 1). These primers were designed based on the humancDNA sequence (GenBank accession no. NM_004797), whichwas aligned to bovine cDNA (AF269230) and human genomic(NT_004962) sequences in order to determine conservedregions and exon–intron boundaries of the gene respectively.An amplicon of approximately 1.8 kb was cloned andsequenced. The sequence was used to design porcine primerpair B (Table 1), which produced a 1417 bp amplicon. Thesequence was extended by an inverse polymerase chain reac-tion (PCR) strategy

Estimates of genetic parameters for feed intake, feeding behavior, and daily gain in composite ram lambs1,2

Our objective was to estimate genetic parameters for feed intake, feeding behavior, and ADG in composite ram lambs ((1/2) Columbia, (1/4) Hampshire, (1/4) Suffolk). Data were collected from 1986 to 1997 on 1,239 ram lambs from approximately 11 to 17 wk of age at the U.S. Meat Animal Research Center near Clay Center, NE. Feeding equipment consisted of an elevated pen with an entrance chute that permitted access to the feeder by only one ram lamb at a time, with disappearance of feed measured by an electronic weighing system. Ram lambs were grouped 11 per pen from 1986 to 1989, and nine per pen from 1990 to 1997. Data were edited to exclude invalid feeding events, and approximately 80% of the data remained after edits were applied. Traits analyzed were daily feed intake (DFI), event feed intake (EFI), residual feed intake (RFI), daily feeding time (DFT), event feeding time (EFT), number of daily feeding events (DFE), and ADG. Feed intake traits of DFI and EFI had estimated heritabilities of 0.25 and 0.33, respectively, whereas estimated heritability of RFI was 0.11. Heritability estimates for feeding behavior traits, including DFT, EFT, and DFE, ranged from 0.29 to 0.36. Average daily gain had an estimated heritability of 0.26. Genetic correlations were positive between all pairs of traits, except for RFI and ADG, and that estimate was essentially zero. Phenotypic correlations were generally similar to genetic correlations. Genetic correlations were large (0.80) between DFI and ADG, intermediate between DFI and RFI (0.61) and between DFT and DFE (0.55), and low (0.17 to 0.31) for the other pairs of traits, with the exception of RFI and ADG (-0.03). Genetic correlations between behavioral traits were greater than correlations between behavioral traits and measures of feed intake or ADG; however, selection for ADG and/or feed intake would be expected to cause some changes in feeding behavior.

Linkage mapping of the porcine chromogranin B (CHGB) gene to chromosome 171

Animal GeneticsVolume 36, Issue 2 p. 168-168 Linkage mapping of the porcine chromogranin B (CHGB) gene to chromosome 171 J. G. Kim, J. G. Kim US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorD. Nonneman, D. Nonneman US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorJ. L. Vallet, J. L. Vallet US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorG. A. Rohrer, G. A. Rohrer US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorR. K. Christenson, R. K. Christenson US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this author J. G. Kim, J. G. Kim US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorD. Nonneman, D. Nonneman US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorJ. L. Vallet, J. L. Vallet US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorG. A. Rohrer, G. A. Rohrer US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this authorR. K. Christenson, R. K. Christenson US Department of Agriculture, Agricultural Research Service, and US Meat Animal Research Center, Clay Center, NE, USA. Present address: Department of Pathology, LSU Health Science Center, School of Medicine, New Orleans, LA, USASearch for more papers by this author First published: 31 March 2005 https://doi.org/10.1111/j.1365-2052.2005.01241.x Ronald K. Christenson ([email protected]) 1 Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume36, Issue2April 2005Pages 168-168 RelatedInformation

Characterization and RH mapping of bovine microsatellites generated from a microdissected BTA20‐specific DNA library

Bovine chromosome 20 (BTA20) is associated with several quantitative trait loci (QTL) for meat tenderness, birth weight, milk yield and composition. Fine mapping of these QTL requires the development of additional informative markers to increase the resolution of the BTA20 genetic and physical maps. A BTA20-specific library was constructed by means of microdissection and microcloning, and screened for dinucleotide repeats with (CA)16 and (GT)16 oligos. A total of 60 new microsatellites (MS) were developed and characterized for polymorphism using the U.S. Department of Agriculture (USDA)/Meat Animal Research Center (MARC) bovine reference family, of which 53 markers were informative in this family. The number of alleles for these loci varied from 1 to 14, with an average of 6.5. Thirty-three of these MSs, together with 105 markers previously mapped to BTA20, were scored on a 7000-rad cattle-hamster whole-genome radiation hybrid panel (SUNbRH), resulting in a high-resolution RH7000 rad map for BTA20.

Association of markers in the bovine CAPN1 gene with meat tenderness in large crossbred populations that sample influential industry sires1,2

Two previously identified single-nucleotide polymorphism markers located within the micromolar calcium-activated neutral protease gene (CAPN1) were evaluated for their association with variation in meat tenderness using one commercial sample of Simmental x Angus crossbred calves and one multibreed, crossbred research herd. The commercial sample included 362 animals sired by 23 registered Simmental bulls bred to unregistered Angus cows and represented current industry animals in which to test the predictive merit of the markers. The second sample was a research herd including 564 steers from the Germplasm Evaluation Cycle VII population at the U.S. Meat Animal Research Center, produced with semen from popular sires of the seven Bos taurus beef breeds with the most registrations in the United States (Angus, Charolais, Gelbvieh, Hereford, Limousin, Red Angus, and Simmental) on Angus, Hereford, and MARC III cows. These animals form a relatively outbred population that constituted a stringent test of the predictive merit of the genetic markers, although small groups were half-sibs. Warner-Bratzler shear force measurements were used to determine tenderness phenotypes for all animals. The populations were genotyped for two markers that predict variation at amino acid positions 316 and 530 of the mu-calpain polypeptide, produced by the CAPN1 gene. Minor allele frequencies for markers 316 and 530 in the commercial sample were 0.17 and 0.37, respectively, and in the Cycle VII animals, were 0.20 and 0.28, respectively. Both markers showed association with shear force in the commercial sample (P = 0.04) and the Cycle VII population (P = 0.02), supporting the hypothesis that they represent potential markers to aid selection for improved meat tenderness in commercial populations of beef cattle in the United States.

Competing risks analysis of lamb mortality in a terminal sire composite population.

Mortality records from birth to weaning of 8,301 lambs from a composite population at the U.S. Meat Animal Research Center were analyzed using a competing risks model. The advantage of the competing risks model over traditional survival analyses is that different hazards of mortality can be assigned to different causes, such as disease, dystocia, and starvation. In this study, specific causes of mortality were grouped into dam-related (DAMR; e.g., dystocia and starvation), pneumonia (PNEU), disease (DIS; excluding pneumonia), and other (OTHER) categories. The hazard of mortality was analyzed using a competing risk approach, where each mortality category was assumed to be independent. Continuous- and discrete-time survival analyses were implemented using sire, animal, and maternal effects mixed models. The continuous-time survival analysis used the Weibull model to describe the hazard of mortality for each category of mortality. Under the discrete-time survival analysis, a complementary log-log link function was used to analyze animal-time data sets using weekly intervals for each category of mortality. Explanatory variables were sex, type of birth, contemporary group, and age of dam. The significant influences of type of birth and age of dam effects were consistent across category of mortality, and the sex effect was significant for all categories except the OTHER category. Estimates of variance components indicated strong maternal effects for all categories except for PNEU. Estimates of additive genetic heritabilities from the discrete maternal effects models were 0.08+/-0.04, 0.09+/-0.18, 0.16+/-0.12, 0.19+/-0.09, and 0.14+/-0.10 for OVERALL (all causes combined), DIS, DAMR, PNEU, and OTHER categories, respectively. Ignoring the cause of the defining event in mortality and longevity studies may hide important genetic differences. Therefore, the effectiveness of breeding programs relying on models that ignore multiple causes of an event in time-to-event data, such as mortality and longevity, could be affected.

Characterization of biological types of cattle (Cycle VI): carcass, yield, and longissimus palatability traits.

Carcass (n = 568) and longissimus thoracis palatability (n = 460) traits from F1 steers obtained from mating Hereford (H), Angus (A), and U.S. Meat Animal Research Center (MARC) III cows to H, A, Norwegian Red (NR), Swedish Red and White (RW), Friesian (F), or Wagyu (W) sires were compared. Data were adjusted to constant age (471 d), carcass weight (356 kg), fat thickness (1.0 cm), percentage of fat trim (24%), and marbling (Small35) end points. For Warner-Bratzler shear force and trained sensory panel traits, data were obtained on longissimus thoracis steaks stored at 2 degrees C for 14 d postmortem. The following comparisons were from the age-constant end point. Carcasses from H- and A-sired steers (377 and 374 kg, respectively) were the heaviest (P < 0.05) and carcasses from W-sired steers (334 kg) were the lightest (P < 0.05). A greater (P < 0.05) percentage of carcasses from A- and W-sired steers graded USDA Choice (88 and 85%, respectively) than carcasses from other sire breeds (52 to 71%). Adjusted fat thickness for carcasses from A-sired steers (1.3 cm) was highest (P < 0.05), followed by H-sired steers (1.1 cm) and W- and F-sired steers (0.9 cm); NR- and RW-sired steers (0.8 cm) had the lowest (P < 0.05) adjusted fat thickness. Longissimus thoracis area was not different (P > 0.05) among sire breeds (mean = 80.6 cm2). Carcass yield of boneless, totally trimmed retail product was least (P < 0.05) for A-sired steers (60.1%), intermediate for H-sired steers (61.5%), and similar (P > 0.05) for all other sire breeds (62.5 to 62.8%). Longissimus thoracis steaks from carcasses of A- (3.7 kg) and W-sired (3.7 kg) steers had lower (P < 0.05) shear force values than longissimus thoracis steaks from other sire breeds (4.1 to 4.2 kg). Trained sensory panel tenderness, juiciness, or beef flavor intensity ratings for longissimus thoracis steaks did not differ (P > 0.05) among the sire breeds. Sire breed comparisons were affected by adjusting data to other end points. Heritability estimates for various carcass, yield, and palatability traits ranged from very low (h2 = 0.06 for percentage of kidney, pelvic, and heart fat) to relatively high (h2 = 0.71 for percentage of retail product yield). Relative to the other sire breeds, W-sired steers had the highest percentage of USDA Choice, Yield grade 1 and 2 carcasses, but their carcasses were the lightest.

Genetic relationships between sex-specific traits in beef cattle: Mature weight, weight adjusted for body condition score, height and body condition score of cows, and carcass traits of their steer relatives1

Data from the first four cycles of the Germplasm Evaluation Program at the U.S. Meat Animal Research Center (USMARC) were used to investigate genetic relationships between mature weight (MW, n = 37,710), mature weight adjusted for body condition score (AMW, n = 37,676), mature height (HT, n = 37,123), and BCS (n = 37,676) from 4- to 8-yr old cows (n = 1,800) and carcass traits (n = 4,027) measured on their crossbred paternal half-sib steers. Covariance components among traits were estimated using REML. Carcass traits were adjusted for age at slaughter. Estimates of heritability for hot carcass weight (HCWT); percentage of retail product; percentage of fat; percentage of bone; longissimus muscle area; fat thickness adjusted visually; estimated kidney, pelvic, and heart fat percentage; marbling score; Warner-Bratzler shear force; and taste panel tenderness measured on steers were moderate to high (0.26 to 0.65), suggesting that selection for carcass and meat traits could be effective. Estimates of heritability for taste panel flavor and taste panel juiciness were low and negligible (0.05 and 0.01, respectively). Estimates of heritability from cow data over all ages and seasons were high for MW, AMW, and HT (0.52, 0.57, 0.71; respectively) and relatively low for BCS (0.16). Pairwise analyses for each female mature trait with each carcass trait were done with bivariate animal models. Estimates of genetic correlations between cow mature size and carcass composition or meat quality traits, with the exception of HCWT, were relatively low. Selection for cow mature size (weight and/or height) could be effective and would not be expected to result in much, if any, correlated changes in carcass and meat composition traits. However, genetic correlations of cow traits, with the possible exception of BCS, with HCWT may be too large to ignore. Selection for steers with greater HCWT would lead to larger cows.

Genetic relationships between sex-specific traits in beef cattle: Mature weight, weight adjusted for body condition score, height and body condition score of cows, and carcass traits of their steer relatives1

Data from the first four cycles of the Germplasm Evaluation Program at the U.S. Meat Animal Research Center (USMARC) were used to investigate genetic relationships between mature weight (MW, n = 37,710), mature weight adjusted for body condition score (AMW, n = 37,676), mature height (HT, n = 37,123), and BCS (n = 37,676) from 4- to 8-yr old cows (n = 1,800) and carcass traits (n = 4,027) measured on their crossbred paternal half-sib steers. Covariance components among traits were estimated using REML. Carcass traits were adjusted for age at slaughter. Estimates of heritability for hot carcass weight (HCWT); percentage of retail product; percentage of fat; percentage of bone; longissimus muscle area; fat thickness adjusted visually; estimated kidney, pelvic, and heart fat percentage; marbling score; Warner-Bratzler shear force; and taste panel tenderness measured on steers were moderate to high (0.26 to 0.65), suggesting that selection for carcass and meat traits could be effective. Estimates of heritability for taste panel flavor and taste panel juiciness were low and negligible (0.05 and 0.01, respectively). Estimates of heritability from cow data over all ages and seasons were high for MW, AMW, and HT (0.52, 0.57, 0.71; respectively) and relatively low for BCS (0.16). Pairwise analyses for each female mature trait with each carcass trait were done with bivariate animal models. Estimates of genetic correlations between cow mature size and carcass composition or meat quality traits, with the exception of HCWT, were relatively low. Selection for cow mature size (weight and/or height) could be effective and would not be expected to result in much, if any, correlated changes in carcass and meat composition traits. However, genetic correlations of cow traits, with the possible exception of BCS, with HCWT may be too large to ignore. Selection for steers with greater HCWT would lead to larger cows.

Breed Comparisons of Weight, Weight Adjusted for Condition Score, Height, and Condition Score of Beef Cows

Breeds were compared for differences in BW (n = 56,731), heights (n = 51,407) and body condition scores (BCS, n = 56,371) of 2- to 8-yr-old cows from four cycles of the Germplasm Evaluation (GPE) Program at the U. S. Meat Animal Research Center (MARC). Angus, Hereford, and topcross cows from 22 breeds of sires were produced. The mixed model for repeated measures of BW, height, and BCS included random additive genetic and permanent environmental effects of the cow. Differences among crosses were significant for all traits. In general, BW, within cycle, was greater for cows sired by breeds of large size and low milk production (Chianina and Charolais) than for those of large size and moderate milk production (Maine Anjou, Salers, and Shorthorn), moderate size and moderate milk production (Angus and South Devon), moderate size and low milk production (Hereford), and small size and low milk production (Galloway and Longhorn). Breeds of moderate size and moderately high milk production (Pinzgauer, Red Poll, and Tarentaise) were even lighter. Cows with Jersey sires were separated from all other breed groups because of light BW. Cows with sires of British origin tended to be lighter than those of continental European origin. Cows with Bos indicus sires (Brahman and Nellore) ranked between other breeds of large and moderate size for BW or for BW adjusted for BCS. In general, adjustment for BCS did not alter rankings of breed groups for differences in cow BW. Differences among breed groups for height closely followed differences for BW.

Covariance functions and random regression models for cow weight in beef cattle.

Data from the first four cycles of the Germplasm Evaluation program at the U.S. Meat Animal Research Center were used to evaluate weights of Angus, Hereford, and F1 cows produced by crosses of 22 sire and 2 dam (Angus and Hereford) breeds. Four weights per year were available for cows from 2 through 8 yr of age (AY) with age in months (AM). Weights (n = 61,798) were analyzed with REML using covariance function-random regression models (CF-RRM), with regression on orthogonal (Legendre) polynomials of AM. Models included fixed regression on AM and effects of cow line, age in years, season of measurement, and their interactions; year of birth; and pregnancy-lactation codes. Random parts of the models fitted RRM coefficients for additive (a) and permanent environmental (c) effects. Estimates of CF were used to estimate covariances among all ages. Temporary environmental effects were modeled to account for heterogeneity of variance by AY. Quadratic fixed regression was sufficient to model population trajectory and was fitted in all analyses. Other models varied order of fit and rank of coefficients for a and c. A parsimonious model included linear and quartic regression coefficients for a and c, respectively. A reduced cubic order sufficed for c. Estimates of all variances increased with age. Estimates for older ages disagreed with estimates using traditional bivariate models. Plots of covariances for c were smooth for intermediate, but erratic for extreme ages. Heritability estimates ranged from 0.38 (36 mo) to 0.78 (94 mo), with fluctuations especially for extreme ages. Estimates of genetic correlations were high for most pairs of ages, with the lowest estimate (0.70) between extreme ages (19 and 103 mo). Results suggest that although cow weights do not fit a repeatability model with constant variances as well as CF-RRM, a repeatability model might be an acceptable approximation for prediction of additive genetic effects.