Genetic evaluation of retail product percentage in Simmental cattle.

The objective of this study was to estimate genetic parameters required for genetic evaluation of retail product percentage (RPP) in Simmental cattle. Carcass weight (HCW), subcutaneous fat thickness (FAT), longissimus muscle area (REA) and kidney, pelvic, and heart fat (KPH) records were available to compute RPP on steers (n = 5171) and heifers (n = 1400) from the American Simmental Association database; animals were sired by 561 Simmental bulls and out of 5886 crossbred dams. Genetic parameters were estimated using residual maximal likelihood and a four trait animal model for the components of RPP including fixed harvest contemporary group effects, random animal genetic effects, and a linear covariate for age at harvest. Heritability estimates were 0.51 +/- 0.05, 0.36 +/- 0.05, 0.46 +/- 0.05, and 0.18 +/- 0.05 for HCW, FAT, REA and KPH respectively. Non-zero genetic correlations were estimated between HCW and REA (rg = 0.51 +/- 0.06) and between REA and FAT (rg = -0.43 +/- 0.08), but other genetic correlation estimates among the component traits were low. As a linear function of its components, heritability and genetic correlations involving RPP were estimated using index methods. The heritability estimate for RPP was 0.41, and genetic correlations were -0.17, -0.83, 0.67, and 0.01 with HCW, FAT, REA and KPH respectively. Therefore, RPP was strongly associated with muscle and fat deposition, but essentially independent of carcass weight and internal body cavity fat. Genetic evaluation of RPP would be straightforward using multiple trait index methods and genetic regression, although the inclusion of KPH would be of marginal value.     

Prediction of yield of retail cuts for native and crossbred Chinese Yellow cattle

Seven hundred and three native and crossbred Chinese Yellow cattle (mean live weight: 523 ± 38 kg) were slaughtered, chilled and segmented. The hot carcass weight (HCW, kg), fat thickness (FT, cm) and rib eye area (REA, cm²) were measured to predict weights and percentages of beef cattle retail cuts. A correlation analysis showed that the HCW and REA were positively correlated with the weights of the total retail cuts (TRC, kg), top grade retail cuts, prime retail cuts and percentage of total carcass weight. A regression analysis indicated that HCW and REA were the best predictors for the weight of total retail cuts (Y = ?16.71 + 0.382 HCW + 0.593 REA), and the HCW explained more of the variation than REA. Meanwhile, HCW and REA accounted for 62% of the variation of percentage of total retail cuts (Y = 43.24 ? 0.025 HCW + 0.170 REA), whereas the REA was more valuable than the HCW. The FT contributed little in estimating weight or percentage of retail cuts.     

A comparison between multivariate Slash, Student's t and probit threshold models for analysis of clinical mastitis in first lactation cows

Robust threshold models with multivariate Student's t or multivariate Slash link functions were employed to infer genetic parameters of clinical mastitis at different stages of lactation, with each cow defining a cluster of records. The robust fits were compared with that from a multivariate probit model via a pseudo‐Bayes factor and an analysis of residuals. Clinical mastitis records on 36 178 first‐lactation Norwegian Red cows from 5286 herds, daughters of 245 sires, were analysed. The opportunity for infection interval, going from 30 days pre‐calving to 300 days postpartum, was divided into four periods: (i) ?30 to 0 days pre‐calving; (ii) 1–30 days; (iii) 31–120 days; and (iv) 121–300 days of lactation. Within each period, absence or presence of clinical mastitis was scored as 0 or 1 respectively. Markov chain Monte Carlo methods were used to draw samples from posterior distributions of interest. Pseudo‐Bayes factors strongly favoured the multivariate Slash and Student's t models over the probit model. The posterior mean of the degrees of freedom parameter for the Slash model was 2.2, indicating heavy tails of the liability distribution. The posterior mean of the degrees of freedom for the Student's t model was 8.5, also pointing away from a normal liability for clinical mastitis. A residual was the observed phenotype (0 or 1) minus the posterior mean of the probability of mastitis. The Slash and Student's t models tended to have smaller residuals than the probit model in cows that contracted mastitis. Heritability of liability to clinical mastitis was 0.13–0.14 before calving, and ranged from 0.05 to 0.08 after calving in the robust models. Genetic correlations were between 0.50 and 0.73, suggesting that clinical mastitis resistance is not the same trait across periods, corroborating earlier findings with probit models.     

An evaluation of the lamb vision system as a predictor of lamb carcass red meat yield percentage

An objective method for predicting red meat yield in lamb carcasses is needed to accurately assess true carcass value. This study was performed to evaluate the ability of the lamb vision system (LVS; Research Management Systems USA, Fort Collins, CO) to predict fabrication yields of lamb carcasses. Lamb carcasses (n = 246) were evaluated using LVS and hot carcass weight (HCW), as well as by USDA expert and on-line graders, before fabrication of carcass sides to either bone-in or boneless cuts. On-line whole number, expert whole-number, and expert nearest-tenth USDA yield grades and LVS + HCW estimates accounted for 53, 52, 58, and 60%, respectively, of the observed variability in boneless, saleable meat yields, and accounted for 56, 57, 62, and 62%, respectively, of the variation in bone-in, saleable meat yields. The LVS + HCW system predicted 77, 65, 70, and 87% of the variation in weights of boneless shoulders, racks, loins, and legs, respectively, and 85, 72, 75, and 86% of the variation in weights of bone-in shoulders, racks, loins, and legs, respectively. Addition of longissimus muscle area (REA), adjusted fat thickness (AFT), or both REA and AFT to LVS + HCW models resulted in improved prediction of boneless saleable meat yields by 5, 3, and 5 percentage points, respectively. Bone-in, saleable meat yield estimations were improved in predictive accuracy by 7.7, 6.6, and 10.1 percentage points, and in precision, when REA alone, AFT alone, or both REA and AFT, respectively, were added to the LVS + HCW output models. Use of LVS + HCW to predict boneless red meat yields of lamb carcasses was more accurate than use of current on-line whole-number, expert whole-number, or expert nearest-tenth USDA yield grades. Thus, LVS + HCW output, when used alone or in combination with AFT and/or REA, improved on-line estimation of boneless cut yields from lamb carcasses. The ability of LVS + HCW to predict yields of wholesale cuts suggests that LVS could be used as an objective means for pricing carcasses in a value-based marketing system.     

Estimates of genetic parameters for live animal ultrasound, actual carcass data, and growth traits in beef cattle

Growth and carcass measurements were made on 2,411 Hereford steers slaughtered at a constant weight from a designed reference sire program involving 137 sires. A second data set consisted of ultrasound measures of backfat (USFAT) and longissimus muscle area (USREA) from 3,482 yearling Hereford cattle representing 441 sires. Restricted maximum likelihood procedures were used to estimate genetic parameters among carcass traits and live animal weight traits from these two separate data sets. Heritability estimates for the slaughter weight constant steer carcass backfat (FAT) and longissimus muscle area (REA) were .49 and .46, respectively. In addition, FAT had a negative genetic correlation with REA (-.37), weaning weight (-.28), and yearling weight (-.13) but positive with marbling (.19) and carcass weight (.36). Marbling was moderately heritable (.35) and highly correlated with total postweaning average daily gain (.54) and feedlot relative growth rate (.62). Heritability estimates for weight constant USFAT and USREA were .26 and .25, respectively. The genetic correlation between weight constant USFAT and USREA was positive (.39), indicating that in these young animals USFAT does not seem to be an indication of maturity. Mean USFAT measures and variability were small (.48 +/- .17 cm, n = 3,482). Results indicate that carcass fat on slaughter steers and ultrasound measures of backfat on young breeding animals may have different relationships with growth and muscling. These relationships need to be explored before wide scale selection based on ultrasound is implemented.     

Exploring the possibilities of genetic improvement from traceability data: An example in the Pirenaica beef cattle

The aim of this study is to explore the potential use of the information generated by the Spanish traceability program (SIMOGAN) for animal breeding purposes in the Pirenaica beef cattle breed. The traits included in the study were: cold carcass weight (CW, n = 20,010), conformation (CON, n = 15,808), fat cover (FC, n = 13,739) and colour (COL, n = 3477) from the SIMOGAN database; and weaning weight (WW, n = 15,561) from the Breeders Association (CONASPI) database. Posterior marginal estimates of genetic parameters were obtained using Bayesian inference, implemented via a Gibbs sampling scheme. Posterior marginal means of heritabilities were 0.34, 0.28, 0.19, 0.23 and 0.38 for CW, CON, FC, COL and WW, respectively. Moreover, posterior marginal distributions of genetic correlations between CW-CON, CW-WW, CON-FC and FC-WW do not include the zero within the Highest Posterior Density (HPD) at 95%, and their posterior mean estimates were 0.30, 0.54, − 0.35 and 0.23, respectively. These results indicate that there is enough genetic variability for selection in CW, CON, FC, COL and WW. The availability of records is potentially abundant at a very low cost, thus they can be easily included in the selection criteria. Consequences of the current selection criteria (WW) and other possible alternatives are discussed.     

Yield grades and cutability of carcass beef with and without kidney and pelvic fat

Cut-out data from 2,550 steer carcasses representing British, Continental and Zebu breeding were analyzed to evaluate yield grade classes based on three equations: 1) Ya = 2.5 + .984 AFT + .0084 HCW - .05 REA + .2 KPF; 2) Yb = same as Ya with intercept changed to 3.2 and KPF deleted; 3) Yc = 3.0 + .984 AFT + .0041 HCW - .03 REA, as proposed by USDA in 1984; where AFT = adjusted fat thickness (cm), HCW = hot carcass weight (kg), REA = rib-eye area (cm2), and KPF = kidney and pelvic fat (%). Essentially boneless, closely trimmed (8 mm) roasts and steaks of the four major retail cuts (MRC) were made from one side of each carcass. Cutability was calculated as: Ca, % = 100 (MRC/side) and Cb,c % = 100 (MRC/side, KPF removed). Cutability increased (P less than .01) an average of two percentage points when KPF was removed. In general, removing KPF from the estimation of cutability and changing the coefficients for REA and HCW resulted in a decrease in the number of carcasses yield graded 1 or 4 and an increase in the number of carcasses in yield grade 2. Redistribution of carcasses was greater for Yc than for Yb. Carcasses classified with equation Yc tended (P greater than .05) to have greater cutability in yield grades 1 and 2, and lower (P less than .01) cutability in yield grades 3, 4 and 5.(ABSTRACT TRUNCATED AT 250 WORDS)     

The value of incorporating carcass trait phenotypes in terminal sire selection indexes to improve carcass weight and quality of heavy lambs

Genetic selection for carcass traits is paramount to maximize the profitability and long‐term sustainability of any meat‐producing livestock species. The main objectives of this research were to evaluate the efficiency of indicator traits for the genetic improvement of lamb carcass traits and to determine the value of including carcass traits into terminal sire selection indexes for the Canadian sheep industry. The carcass traits included hot carcass weight (HCW), fat depth at the GR site (FATGR) and average carcass conformation score (AVGCONF), and were measured on heavy lambs (slaughter age less than 365 days and HCW greater than 16.3 kg) in commercial abattoirs. Growth traits were found to be moderately efficient indicator traits for the genetic improvement of HCW but selection on ultrasound traits was necessary to substantially improve the carcass quality traits (FATGR and AVGCONF). Economic selection indexes were designed by adding various combinations of carcass traits into the Canadian Sheep Genetic Evaluation System terminal indexes. Records measured on individuals and progeny were assumed to be the sources of information for live animal and carcass traits, respectively. The changes in index accuracy, efficiency and expected correlated response were used to assess the value of their inclusion. HCW was found to have a large economic value, and its inclusion into terminal selection indexes was expected to substantially increase their accuracy (0.08–0.12 points) and efficiency (20%–30%). However, further including FATGR (measured 110 mm from the carcass midline over the 12th rib) and AVGCONF had little impact on the accuracy (≤0.03) and efficiency (1%–7%) of the proposed indexes. Thus, the inclusion of carcass traits into the existing terminal selection indexes could be beneficial for the genetic improvement of HCW, but further research is needed to determine optimal methods of increasing carcass fatness and muscularity.     

Genetic evaluation of beef carcass data using different endpoint adjustments

Carcass data from 6,795 Simmental-sired animals born from 1992 to 2001 were used to determine whether adjustment to a constant age, back-fat, HCW, or marbling score would result in differences in heritability of the carcass traits and, correspondingly, if EPD calculated using those variance components and adjustments would result in sire reranking. The endpoints were age (EPA), backfat (EPF), HCW (EPC), or marbling (EPM). The traits analyzed were 12th-rib backfat (FAT), HCW, marbling (MRB), LM area (LMA), and percentage retail cuts (PRC). The data were analyzed using an animal model, where contemporary group was included as a fixed effect and was composed of slaughter date, sex, and herd. Random effects included in the model were direct genetic and residual. Estimates of heritability ranged from 0.12 to 0.14, 0.32 to 0.34, and 0.26 to 0.27 for FAT, HCW, and LMA, respectively, for the corresponding endpoints. Heritability for MRB was estimated to be 0.27 at all endpoints. For PRC, estimates of heritability were more variable, with estimates of 0.23 +/- 0.05, 0.32 +/- 0.05, 0.21 +/- 0.05, and 0.20 +/- 0.04 for EPA, EPF, EPC, and EPM, respectively. However, because the EPF and EPC adjustments adjust for a component trait of PRC (FAT and HCW, respectively), they may be altering the trait to one different from PRC. Spearman rank correlations between EPD within a trait using EPA compared with the other endpoints were >0.90 (P < 0.01) for FAT, HCW, MRB, and LMA. For PRC, Spearman rank correlations with EPA EPD were 0.73 (P < 0.01), 0.93 (P < 0.01), and 0.95 (P < 0.01) for EPF, EPC, and EPM, respectively. For most traits and endpoints, there was little reranking among sires when alternative endpoints were used. However, adjusting PRC to EPF appears to result in a greater heritability and substantial re-ranking of sires, potentially due to the adjustment changing the trait to one other than PRC.     

Direct and maternal genetic relationships of lamb live weight and carcass traits in Swedish sheep breeds

Possibilities to include carcass traits recorded at commercial slaughterhouses in the genetic evaluation of sheep in Sweden were investigated by estimating direct and maternal genetic parameters for 4‐month weight (4MW), carcass weight (CW), carcass fatness grade (FAT), and carcass fleshiness (FLESH) using multiple‐trait animal models. Data included two sets of breeds, the so‐called white breeds (Swedish landrace breeds, Texel, Dorset, Oxford Down, Suffolk, East Friesian Milk Sheep, and Swedish crossbred) and the Gotland breed. There were 30 625 observations on 4MW and 5062 observations on carcass traits for the white breeds. For the Gotland breed the numbers were 43 642 and 7893, respectively. The results showed that it is feasible to use field‐recorded carcass traits in the genetic evaluation. To consider the effects of selection and to utilize all information in an optimal way multiple trait animal models should be used. Direct and maternal heritabilities for 4MW and CW varied between 0.04 and 0.18 and heritabilities for FAT and FLESH between 0.21 and 0.29. Direct and maternal genetic correlations between 4MW and CW were high (0.61–0.97). Genetic correlations were higher between the weights and FLESH (0.11–0.62) than between the weights and FAT (?0.23 to 0.40). Genetic correlations between FAT and FLESH were moderate (0.38–0.45). Heritabilities for CW were higher if 4MW was included in the analyses and the effect of selection on 4MW was stronger for CW than for FAT or FLESH. The importance of maternal effects on carcass traits was discussed.     

Prediction of Future Carcass Traits in Stocker Cattle at the Conclusion of Grazing

Prediction of eventual carcass traits in stocker cattle at the conclusion of grazing could be useful for culling, co-mingling of animals, feedlot pen assignments, and making management decisions in the feedyard. Ultrasound measures of 12th to 13th rib longissimus area (ULA) and fat thickness (UFAT), and off-pasture BW (OPBW) were collected from yearling cattle (n = 261) at the conclusion of grazing in two experiments that evaluated stocking rate and grazing management effects on rye (Secale cereale L.) annual ryegrass (Lolium multiflorum Lam.) pastures. Carcasss data were subsequently recorded at harvest following feedyard finishing to a visual 1-cm backfat. Correlations were analyzed to determine relationships between carcass traits and ULMA, UFAT, body condition measure (BCM), and OPBW. Ultrasound measures, breed type (BRDT; n = 4), gender (steers and heifers), and feedlot days on feed (DOF) were evaluated in multiple regression models to determine whether these variables influence eventual carcass percentage retail product, kilograms retail product (KRP), hot carcass weight (HCW), and marbling score. Ultrasound FAT and BCM were negatively correlated with percentage retail product, KRP, and HCW and were positively correlated with marbling score. All reduced regression models had R² values of between 0.15 and 0.63, and models with inputs of UFAT and OPBW consistently had the numerically greatest R² values and least RMSE. Multiple regression analyses indicated that prediction of carcass traits from stocker cattle ultrasonic measurements at the conclusion of grazing were possible, but improvement in the models will be necessary to reduce error and improve reliability.     

Genomic imprinting variances of beef carcass traits and physiochemical characteristics in Japanese Black cattle

The objective of this study was to estimate variance components related to imprinting for carcass traits and physiochemical characteristics in Japanese Black cattle. The carcass records obtained from 4,220 Japanese Black feedlot cattle included carcass weight (CW), rib eye area (REA), rib thickness, subcutaneous fat thickness, and beef marbling score (BMS), and the physiochemical characteristics were fat, moisture, glycogen per proportion of moisture content, oleic acid, and monounsaturated fatty acids (MUFA). To detect gametic effects, an imprinting model was fitted. High additive heritabilities were estimated for all traits (from 0.516 for glycogen to 0.853 for fat) and were reduced in Mendelian heritability. The range of the differences was from 0.002 (CW) to 0.331 (fat and moisture), and the reductions were due to their imprinting variances. The ratio of the imprinting variance to the total additive genetic variance for REA (0.374), BMS (0.291), fat (0.387), moisture (0.388), and MUFA (0.337) were large (p < 0.05). These imprinting variances were due to the maternal contribution and suggested the existence of maternally expressed genomic imprinting effects on the traits in Japanese Black cattle. Therefore, maternal gametic effects should be considered in breeding programs for Japanese Black cattle.     

Genetic parameters for carcass traits of field progeny and their relationships with feed efficiency traits of their sire population for Japanese Black cattle

Genetic parameters for carcass traits of 1774 field progeny (1281 steers and 493 heifers), and their genetic relationships with feed efficiency traits of their sire population (740 bulls) were estimated with REML. Feed efficiency traits included feed conversion ratio (FCR) and residual feed intake (RFI). RFI was calculated by the residual of phenotypic (RFI_phe) and genetic (RFI_gen) regression from the multivariate analysis of feed intake on metabolic weight and daily gain. Progeny traits were carcass weight (CWT), rib eye area (REA), rib thickness (RBT), subcutaneous fat, yield estimate (YEM), marbling score (MSR), meat quality grade, meat color, fat color, meat firmness and meat texture. The estimated heritability for CWT (0.70) was high and heritabilities for all the other traits were moderate (ranged from 0.32 to 0.47), except for meat and fat color and meat texture which were low (ranged from 0.02 to 0.25). The high genetic correlation (0.62) between YEM and MSR suggests that simultaneous improvement of high carcass yield and beef marbling is possible. Estimated genetic correlations of RFI (RFI_phe and RFI_gen) of sires with CWT (− 0.60 and − 0.53) and MSR (− 0.62 and − 0.50) of their progeny were favorably negative indicating that the selection against RFI of sires may have contributed to produce heavier carcass and increase in beef marbling. The correlated responses in CWT, REA and RBT of progeny were higher to selection against RFI than those to selection against FCR of sires. This study provides evidence that selection against RFI is preferred over selection against FCR in sire population for getting better correlated responses in carcass traits of their progeny.     

Effect of carcass price fluctuations on genetic and economic evaluation of carcass traits in Japanese Black cattle

The objectives of this study were 1) to investigate the effect of changes in carcass market prices due to bovine spongiform encephalopathy (BSE) occurrences on estimates of genetic parameters and economic weights for carcass traits; and 2) to compare direct and indirect approaches for prediction of genetic merit of Japanese Black cattle for profitability of their progeny. The direct approach utilized estimated breeding values of carcass prices, whereas in the indirect approach, selection indices were constructed as products of economic weights and breeding values of component traits. Data were composed of 80,191 carcass records divided into 5 periods based on changes in carcass prices as a result of occurrences of BSE in Japan and the United States. The periods ranged from a period before occurrence of BSE in Japan to a period of beef import restrictions and a rise in prices. Carcass traits analyzed included HCW, LM area, rib thickness, subcutaneous fat thickness, and marbling score (MS). Price traits included carcass unit price and carcass sale price. Estimates of heritability for price traits were moderate (0.32 to 0.46) and slightly sensitive to changes in carcass market prices. Genetic correlations of HCW and LM area with price traits increased and that between MS and carcass sale price decreased with period, whereas estimates of genetic correlation between MS and carcass unit price were high in all periods (0.96 to 0.98). Economic weights for carcass traits varied with periods because carcass prices were highly sensitive to economic importance of traits. Nevertheless, correlations between within-period breeding values for price traits estimated using direct and indirect approaches were high (0.92 to 0.99). This result indicates that selection realized by direct and indirect approaches will provide very similar results. A comparison among within-approach breeding values estimated in different periods showed that the largest differences in breeding values of sires for price traits were between the periods after occurrences of BSE in Japan and in the United States. Economic effects of BSE occurrences influenced the importance of carcass traits and economic merits of price traits through a change of carcass prices from period to period, irrespective of the approach taken in determining the genetic merit of breeding animals for profitability of their progeny.     

Selection for lean weight based on ultrasound and CT in a meat line of sheep

Genetic parameters for carcass traits in lambs at weaning (average age of 128 days) measured by ultrasound (n = 1821) and computer tomography (CT) (n = 234), and response to selection for ultrasound eye muscle depth (UMD) and carcass LEAN weight, were estimated. The research flock comprised a meat line (ML) and a control line (CL) of Norwegian White Sheep. The ML was crossed with Texel from 1998, and selected for UMD from 1993 to 2001, and for LEAN weight from 2001 to 2004. For CT scanning, a mean of 23 images was taken per animal. Genetic parameters were estimated with univariate and bivariate mixed-animal models using AIREML, including all animals with records and their relatives. The statistical models included fixed effects, live weight or age of lamb at weaning (covariate), and a random genetic effect.

Heritability estimates for weight of LEAN, FAT and BONE were 0.57, 0.29 and 0.51 using model corrected for live weight. The heritability estimates were lower when these traits were adjusted for age. High genetic correlation was found between LEAN and UMD (0.70), and between carcass FAT and ultrasound fat depth (UFD) (0.82). The genetic trend for UMD regressed on year of birth was significantly greater for ML than CL in 2004.     

Factors affecting carcass value and profitability in early-weaned Simmental steers: I. Five-year average pricing

In a 4-yr study, early-weaned Simmental steers (n = 192) of known genetics were individually fed to determine genetic, performance, and carcass factors explaining variation in carcass value and profitability. Steers were weaned at 88.0 +/- 1.1 d of age and pen-fed a high-concentrate diet (108.99 dollars/t) for 84.5 +/- 0.4 d before allotment. Calves were implanted with Synovex C at weaning and successively with Synovex S (Fort Dodge Animal Health, Fort Dodge, IA) and Revalor S (Intervet, Inc., Millsboro, DE). Steers consumed a 90% concentrate diet (98.93 dollars/t), consisting primarily of coarse cracked corn and corn silage, for 249.7 +/- 0.7 d and slaughtered at 423.3 +/- 1.4 d of age. Five-year price data were collected for feedstuffs, dressed beef, and grid premiums, and discounts. Average dressed beef price was 110.67 dollars/45.4 kg. Premiums (dollars/45.4 kg) were given for Prime (5.62 dollars), Average Choice (1.50 dollars), and yield grades (YG) 1 (2.46 dollars), 2A (1.31 dollars), and 2B (1.11 dollars). Discounts (dollars/45.4 kg) were given for Standard (-16.85 dollars), Select (-8.90 dollars), and YG 3A (-0.12 dollars), 3B (-0.19 dollars), 4 (-14.16 dollars), and 5 (-19.56 dollars). Discounts were given for HCW extremes as well (409 to 431 kg, -0.64 dollars; 432 to 454 kg -11.39 dollars; > 454 kg, -19.71 dollars). Input costs included annual cow costs (327.77 dollars), veterinary/medical and labor (35 dollars per animal), feed markup (22 dollars/t), yardage (0.25 dollars/d per animal), and interest (10%). Dependent variables were carcass value and profit per steer. Independent variables were year, weaning weight EPD, yearling weight EPD, marbling EPD, DMI, ADG, G:F, HCW, calculated YG, and marbling score (MS). Carcass value was correlated (P < 0.05) with yearling weight and marbling EPD, DMI, ADG, feed efficiency, HCW, and MS. Carcass weight, MS, and YG accounted for nearly 80% of the variation in carcass value among steers, explaining 51, 10, and 8%, respectively. Profit was correlated (P < 0.05) with DMI, ADG, feed efficiency, HCW, and MS. Carcass weight, MS, YG, and DMI accounted for nearly 78% of the variation in profit among steers, explaining 21, 18, 12, and 3%, respectively. Carcass weight was the most critical factor contributing to carcass value, whereas BW and carcass quality were the primary factors affecting steer profitability. These models represent the relative importance of factors contributing to value and profitability in early-weaned Simmental steers based on historical pricing scenarios.     

Impact of including the cause of missing records on genetic evaluations for growth in commercial pigs

It is of interest to evaluate crossbred pigs for hot carcass weight (HCW) and birth weight (BW); however, obtaining a HCW record is dependent on livability (LIV) and retained tag (RT). The purpose of this study is to analyze how HCW evaluations are affected when herd removal and missing identification are included in the model and examine if accounting for the reasons for missing traits improves the accuracy of predicting breeding values. Pedigree information was available for 1,965,077 purebred and crossbred animals. Records for 503,716 commercial three-way crossbred terminal animals from 2014 to 2019 were provided by Smithfield Premium Genetics. Two pedigree-based models were compared; model 1 (M1) was a threshold-linear model with all four traits (BW, HCW, RT, and LIV), and model 2 (M2) was a linear model including only BW and HCW. The fixed effects used in the model were contemporary group, sex, age at harvest (for HCW only), and dam parity. The random effects included direct additive genetic and random litter effects. Accuracy, dispersion, bias, and Pearson correlations were estimated using the linear regression method. The heritabilities were 0.11, 0.07, 0.02, and 0.04 for BW, HCW, RT, and LIV, respectively, with standard errors less than 0.01. No difference was observed in heritabilities or accuracies for BW and HCW between M1 and M2. Accuracies were 0.33, 0.37, 0.19, and 0.23 for BW, HCW, RT, and LIV, respectively. The genetic correlation between BW and RT was 0.34 ± 0.03, and between BW and LIV was 0.56 ± 0.03. Similarly, the genetic correlation between HCW and RT was 0.26 ± 0.04, and between HCW and LIV was 0.09 ± 0.05, respectively. The positive and moderate genetic correlations between BW and other traits imply a heavier BW resulted in a higher probability of surviving to harvest. Genetic correlations between HCW and other traits were lower due to the large quantity of missing records. Despite the heritable and correlated aspects of RT and LIV, results imply no major differences between M1 and M2; hence, it is unnecessary to include these traits in classical models for BW and HCW.     

Factors affecting carcass value and profitability in early-weaned Simmental steers: II. Days on feed endpoints and sorting strategies

In a 4-yr study, early-weaned Simmental steers (n = 192) of known genetics were individually fed to determine EPD, performance, and carcass measurements explaining variation in carcass value and profitability across incremental days on feed (DOF) when sorted by HCW, calculated yield grade (YG), or at their highest profit endpoint (BEST). Steers were weaned at 88.0 +/- 1.1 d of age, pen-fed a high-concentrate diet for 84.5 +/- 0.4 d, individually fed for 249.7 +/- 0.7 d, and slaughtered at 423.3 +/- 1.4 d of age. Carcass weight, YG, and marbling score (MS) were predicted using real-time ultrasound throughout the finishing period to calculate carcass value and profitability at 90, 60, 30 d preslaughter and under three individual sorting strategies. Sorting strategies included marketing the 25 and 50% heaviest HCW, the highest YG at d 60 and 30, or the remaining 25% at 0-d endpoints. Independent variables were year, weaning weight EPD, yearling weight EPD, marbling EPD, DMI, ADG, HCW, YG, and MS. Profit was quadratic in response to increased DOF; the greatest economic return was noted on d 30 (pre-slaughter). Final weight, DMI, HCW, MS, and YG increased (linear; P < 0.001) with additional DOF, and ADG and G:F decreased (linear; P < 0.001). Total cost of gain was quadratic (P < 0.001), and incremental cost of gain rose at an increasing rate (quadratic; P < 0.001) with increased DOF. With increasing DOF, HCW importance decreased from 58 to 21%; MS was variable, ranging from 18 to 23%; and YG and DMI were minor contributors to profit variation. Among sorting strategies, final BW and HCW were greater for BEST, whereas other measurements were similar. Sorting individuals by HCW, YG, or at BEST increased profitability 3.70 dollars, 2.52 dollars, or 30.65 dollars over the optimal group DOF endpoint (d 30). Retrospective analyses illustrated that sorting does not need to pinpoint each animal's profit optimum to result in economic gains; rather, increasing HCW and decreasing weight- and YG-related penalties improved profitability. Opportunities may exist with existing and new technology to uniformly allocate cattle into feeding and marketing groups, decrease overfeeding, and increase carcass value and profitability.     

Effects of growth type on carcass traits of pasture- or feedlot-developed steers.

Carcasses of 342 steers of known genetic backgrounds from four fundamentally different growth types were developed either on pasture or feedlot regimens to study differences in carcass traits. Growth types were large framed-late maturing (LL), intermediate framed-intermediate maturing (II), intermediate framed-early maturing (IE), and small framed-early maturing (SE). Five calves from each growth type were assigned to each regimen in each year of a 9-yr study. Eighteen steers were removed from the study because of accident or illness. Data collected were preslaughter shrunk BW (SBW); hot carcass weight (HCW); chilled carcass weight (CCW); dressing percentage (DRESS); fat thickness at the 12th and 13th-rib interface (FAT); percentage kidney, pelvic, and heart fat (KPH); longissimus muscle area (LMA); marbling score (MARB); quality grade (QG); and yield grade (YG). Differences in carcass traits reflected genetic differences among growth types. The LL steers had heavier BW, HCW, and CCW and larger LMA (P < .05) than steers of other growth types, regardless of development regimen. Among pasture-developed steer carcasses, IE and SE steers had higher (P < .05) MARB and QG than either LL or II steers. Carcasses of large framed-late maturing steers had the lowest (P < .05) MARB and QG of the growth types. Carcasses of the II, IE, and SE steers had a higher (P < .05) numerical value for YG than carcasses of the LL steers. Among the carcasses of the feedlot-developed steers, IE and SE steers had the highest (P < .05) MARB and QG. Carcasses from the IE and SE steers were fatter (P < .05) than those from LL or II steers. Carcasses of the LL steers had the lowest percentage of KPH of growth types developed in the feedlot. No difference was observed in KPH for carcasses of II, IE, and SE steers. The LL steer carcasses had the lowest numerical value for YG of all growth types. These data indicate that variation existed among carcass traits for the four growth types and that carcass traits influenced by fatness were greater and more attainable in the feedlot-developed steers using current methods of evaluation.     

The effects of shade on performance,carcass classes and behaviour of heat-stressed feedlot cattle at the finisher phase

The study aimed to determine the impact of shade on the performance, carcass class and behaviour using 146 crossbred steers and bulls during the finishing phase on a commercial feedlot in February. Treatments were (1) shade and (2) no shade. Average daily gain (ADG), DMI, and feed efficiency were measured, and hot carcass weight (HCW) and grades were collected at slaughter. The proportion of animals within a pen engaged in various behavioural activities (standing, lying, feeding and panting) was recorded. Five randomly selected individual animals per treatment were monitored every 2 min between 0700 and 1600 hours to determine the time spent on each of the above activities. Shade improved the final body weight (P  <  0.0001), ADG (P  =  0.079), and HCW by 8.33 kg (P  <  0.05). Shade increased (P  <  0.05) the feeding activity but decreased (P  <  0.05) panting behaviour. Shade conferred an economic benefit of R2.03 head⁻¹ week⁻¹, and thus would reduce heat stress and increase the feedlot profitability.