J. W. Wilton

Genetic parameters and breed differences for feed efficiency, growth, and body composition traits of young beef bulls

Genetic associations between feed efficiency, growth, and live ultrasound measured body composition traits were studied in purebred beef bulls of six breeds in Ontario bull test stations from 1991 to 2000. Feed traits included average daily feed intake (FI), feed conversion ratio (FCR), and residual feed intake [feed intake adjusted for production alone (RFIp) or production and backfat thickness (RFIb)]. Growth traits were average daily weight gain (ADG), mid-test metabolic weight (MW), hip height (HH), and scrotal circumference (SC). Body composition traits included ultrasound backfat thickness (BF), longissimus muscle area (LMA), and predicted percentage of intramuscular fat (IFAT). Bulls were measured every 28 d for weight and individual feed intake, and at the end of test for ultrasound body composition traits. Number of records per trait ranged from 2284 (FI) to 13 319 (ADG). Fixed effects of test group, breed and end of test age (within breed), and random effects of animal and herd of origin were mo...

Effects of gender and breed on carcass traits, chemical composition, and palatability attributes in Hereford and Simmental bulls and steers

The effects of gender and breed on carcass and chemical composition, and palatability attributes were investigated in 222 Hereford and Simmental bulls and steers. Cattle were progeny of 12 Hereford and 17 Simmental sires using six half-sibs per sire. Bulls were fed a 64% TDN diet to slaughter endpoints of either 4, 7, or 10 mm backfat. Steers were fed diets containing up to 80% TDN until cattle achieved 7 to 10 mm backfat. Gender effects were confounded with diet to take into account differences in commercial cattle feeding vs. bull testing. Gender by breed interactions (P < 0.05) were present for carcass traits due to large between breed differences for bulls as limited ability for Simmental bulls to fatten resulted in deposition of more lean tissue. Gender by breed interactions (P < 0.05) were present for shear, and tenderness and flavour attributes. Beef from Simmental bulls was characterized with less flavour intensity, and tough due to high scores for shear and time spent chewing, and low scores for softness and tenderness. Shear, tenderness, and flavour attributes were similar among Herefords of both genders and Simmental steers. Palatability attributes for Hereford bulls managed in a bull test program were non-significantly different than those from Hereford steers managed in a feedlot environment, suggesting that palatability attributes for steers could be predicted from bulls. This was not the case with Simmental bulls probably due to limited fattening ability on a relatively low energy bull test diet.

Comparisons of economic values with and without risk for livestock trait improvement

This paper investigates the effect of incorporating risk in the derivation of economic values for livestock trait improvement. Two ways of obtaining economic values were contrasted, without consideration of risk (traditional economic values) and with incorporation of variance of profit and risk attitudes of livestock producers (risk-rated economic values). Traditional economic values were derived using a profit model, whereas risk-rated economic values were derived using a risk-rated profit model. A simplified example was considered for selection for the feedlot phase of beef production. One output trait (average daily gain) and one input trait (daily dry matter intake) and one management variable were considered. Risk was defined as the variance of profit and producer’s risk attitude. Traditional economic values and risk-rated economic values differed in both absolute and relative terms. When relative economic values were considered, differences between traditional economic values and risk-rated economic values increased with risk premium. Differences were greater without optimisation of management than with optimisation, although in the example used there was limited impact on expected responses to selection in the component traits. Including risk preferences in breeding goals affects the cost–benefit analysis of breeding programs and might affect directions for selection.

Effect of management strategy on growth performance, carcass characteristics, fatty acid composition, and palatability attributes in crossbred steers

Crossbred steers (n = 136) were used to evaluate the effect of management strategy on growth performance, carcass characteristics, and fatty acid composition and palatability attributes of beef. Management strategies included: (1) high grain (75% high moisture corn) finishing (HG), or (2) backgrounding with restricted feeding of an alfalfa silage ration for 112 d, followed by HG until slaughter (BKG). Steers were slaughtered at 8–10 mm ultrasound backfat. Backgrounding increased (P 0.10) by management strategy. Longissimus muscle palatability attributes and shear force did not differ (P > 0.10) between management strategies, whereas BKG increased (P < 0.03) softness, overall tenderness, chewiness, and rate of breakdown scores, and decreased (P < 0.09) juiciness scores in semitendinosus ...

Effects of diet, breed and slaughter endpoint on growth performance, carcass composition and beef quality traits in Limousin and Charolais steers

Ninety-six Charolais and Limousin steers were used to evaluate 75% grain (whole barley or corn) diets and two slaughter endpoints (7 mm backfat or 568 kg liveweight) in an experiment designed to constrain carcass weights to under approximately 341 kg yet produce optimal beef quality. Each breed was represented by eight progeny from each of six sires. The trial was terminated after 281 d feeding regardless of individual steers attaining designated slaughter endpoints. Limited availability of dietary energy in whole-barley diets resulted in decreased (P < 0.01) average daily gain and increased (P < 0.01) dry matter intake, feed/gain and days on feed for barley- vs. corn-fed cattle. Charolais outgained (P < 0.05) Limousin but dry matter intake was similar on a g BW00.75 basis. Feeding to 568 kg liveweight was associated with high (P < 0.10) ADG and decreased (P < 0.05) feed/gain compared with feeding to 7 mm. Corn feeding increased (P < 0.001) carcass weights, fat deposition and longissimus muscle area. Lean...

Effects of breed and dietary energy content within breed on growth performance, carcass and chemical composition and beef quality in Hereford and Simmental steers

Forty-eight Hereford and 60 Simmental steers were used to evaluate breed differences as affected by dietary energy content on growth performance, carcass and chemical composition, and beef quality. Diets were based on corn silage, alfalfa haylage, whole corn, and SBM and were formulated to provide 2.52 to 2.81 Mcal kg−1 ME and 11.7 to 12.6% protein in the growing phase and 2.69 to 2.86 Mcal kg−1 ME and 9.7 to 10.4% protein in the finishing phase. Low- and high-ener-gy diets were formulated for each breed with the high-energy diet for Hereford serving as the low-energy diet for Simmental. Steers were slaughtered after attaining 8 to 10 mm backfat determined by ultrasound. Higher energy diets increased (P < 0.09) average daily gain (ADG) and feed efficiency within both breeds. Hereford gained more rapidly (P = 0.074) and were more (P = 0.001) efficient in converting feed to gain than Simmental. High-energy diets decreased (P = 0.001) days on feed for both breeds and increased (P = 0.001) carcass weights for...

The determination and correlation of reproductive parameters of performance-tested Hereford and Simmental bulls

Purebred Hereford and Simmental bulls (n = 120), managed similarly to bulls in the Ontario Bull Evaluation Program, were evaluated for reproductive parameters. Four diets, equivalent except for the form of dietary fiber, were fed in a growth performance trial. Diet had no direct effect (P > 0.10) on any of the reproductive variables examined. Of the 117 bulls that had complete breeding soundness evaluations, 75% were classified as satisfactory potential breeders, 24% as questionable potential breeders and 1% as unsatisfactory potential breeders. The 2 breeds were significantly different (P < 0.05) for several end of test parameters. When controlling for age and weight differences, Herefords had a higher backfat thickness, smaller scrotal circumference, lower paired testicular weight and lower epididymal weight. Semen morphology and motility did not differ (P > 0.10) between the breeds. When examining simple correlations, scrotal circumference was highly correlated with paired testicular weight, moderately correlated with epididymal weight, daily sperm production and extragonadal sperm reserves, and negatively correlated with backfat thickness. Scrotal circumference was not related to backfat thickness when controlling for breed effects. The degree of germinal epithelium loss was moderately and negatively correlated with the percentage of spermatozoa with normal morphology and progressive motility, epididymal sperm reserves and epididymal weight, but was not correlated with scrotal circumference.

Herd of origin effect on weight gain of station-tested beef bulls

The effect of herd of origin on genetic evaluation of weight gain of beef bulls in central test stations was examined by univariate and bivariate analyses, which included bull’s estimated weight gain on test (BEG) and pre-weaning gain (WG) of bulls and their contemporaries in the herd of origin. Bulls were weighed every 28 days on 112 or 140-day station test. BEG was estimated fitting fixed linear regressions to the weights on test of each bull. The bivariate model included random direct additive genetic and dam effects and fixed breed effects for both traits, fixed management group and sex of calf by age of cow effects for WG and fixed test group and random herd of origin by year (HY) effects for BEG. Variance components and EBV were estimated applying models with or without HY effect, which were compared using likelihood ratio test and two information criteria. The effect of HY was significant on BEG, contributing around 8% to total phenotypic variation. Inclusion of HYeffect caused EBV to re-rank among top bulls (rank correlation of 0.85 and 0.75 among 5% and 1% best bulls, respectively). Interaction of HY by sire was shown not to be of concern. D 2003 Elsevier B.V. All rights reserved.

Genetic correlations among indicator traits for carcass composition measured in yearling beef bulls and finished feedlot steers

Genetic correlations were examined among 10 live growth and ultrasound traits measured in yearling beef bulls (n = 2172) and four carcass traits measured in crossbred finished feedlot steers (n = 1031). Heritabilities ranged from 0.13 (bull ultrasound longissimus muscle width) to 0.83 (yearling bull hip height). Genetic correlations indicated that selecting yearling bulls for increased growth rate and hip height would lead to higher carcass weight, increased longissimus muscle area and reduced levels of carcass marbling in steers. Bull ultrasound fat depth was positively associated with both carcass fat depth and marbling score. Most ultrasound longissimus muscle size measurements in bulls were positively associated with each other and with carcass longissimus muscle area in steers, but the magnitude of the genetic correlation with carcass measurements depended on the bull longissimus muscle size trait in question. This suggests that longissimus muscle shape in bulls may be related to carcass weight, fat ...

Effects of skeletal separation method and postmortem ageing on carcass traits and shear force in cull cow beef

Mandell, I. B., Campbell, C. P., Quinton, V. M. and Wilton, J. W. 2006. Effects of skeletal separation method and postmortem ageing on carcass traits and shear force in cull cow beef. Can. J. Anim. Sci. 86: 351‐361. Sixty-six cull cow carcasses were subjected to skeletal separation methods for improving beef tenderness as evaluated using shear force. Forty-one carcasses were used to evaluate the effect on longissimus muscle shear force from skeletal separation at various sites including: (1) the 11th thoracic vertebra, (2) the 12th thoracic vertebra, and (3) the 6th thoracic and 5th lumbar vertebrae. Longissimus muscle steaks from the posterior and anterior loin and posterior rib were aged for 2, 7, 14, and 28 d. Twenty-five carcasses underwent skeletal separation processing in the round with severing of the ischium and the junction between 4th/5th sacral vertebrae. Semimembranosus, semitendinosus, biceps femoris, vastus lateralis, and rectus femoris muscles were processed into steaks and aged for 2, 7, 14, and 28 d. Skeletal separation techniques involving thoracic and lumbar vertebrae decreased (P < 0.04) shear force in the posterior rib and anterior loin but not in the posterior loin. Shear force continued to decrease (P < 0.01) as postmortem ageing duration increased. The semimembranosus was the only muscle in the round in which shear force decreased (P < 0.01) with skeletal separation. Postmortem ageing for at least 14 d decreased (P < 0.06) shear force in semimembranosus and vastus lateralis steaks while there were no further decreases in shear force after 7 d ageing for semitendinosus and rectus femoris steaks. Skeletal separation increased (P < 0.10) sarcomere length in all muscles studied. Skeletal separation techniques have the potential to improve tenderness in the longissimus and semimembranosus muscles, which may increase utilization of cull cow beef.