At weaning and again after postweaning gain tests, height and width at hips, height at withers, body length, girth, head length and width, muzzle width, and cannon bone circumference measurements were obtained from Angus and Hereford bulls and heifers born in 1964, 1984, and 1985 (n = 989). The cattle were from the initial and final two calf crops selected for postweaning gain when fed either a high-concentrate diet or an all-hay diet. Analysis of variance and canonical discriminant analysis were used to examine the relationships among body measurements and major sources of variation (breed, year of birth, sire within breed and year, diet, sex of calf, age of dam, and the regression on age of calf). Canonical discriminant analysis indicated that one underlying variate explained nearly 90% of the total variation among the weaning measurements, whereas three variates were required to account for that proportion in the end-of-test measurements. At both measurement times, the first canonical variate was associated with year of birth, the second with sex of calf, and the third with dietary energy. Correlations between each canonical variate and the original body measurements indicated that year of birth (variate 1) was most closely associated with body length and cannon bone circumference at weaning and with body length and height at hips (but not withers) at end of test. Sex of calf (variate 2) was associated most closely with width of muzzle and head. Diet (variate 3) was associated with heart girth. Faster-growing cattle were longer in body, but not necessarily taller.

Postweaning gain performance and individual feed intake on 271 Hereford and 263 Angus bulls were recorded during three 168-d test periods from 1984 to 1986. Each breed was composed of two lines and within each breed bulls were fed either a high-energy (HD) or a medium-energy (MD) diet. Energy intake was partitioned into energy for maintenance and growth based on predicted individual animal requirements. Estimates of heritability were obtained using Restricted Maximum Likelihood with an individual animal model including fixed effects of year, diet, and covariates of initial weight and backfat change by breed and with line effects for overall data. Bulls fed the HD grew faster and had higher metabolizable energy intake per day (MEI), residual feed consumption (RFC), and gross and net feed efficiency (FE and NFE) (P < .001) than those fed the MD. Estimates of heritability for Hereford and Angus bulls, respectively, were .46 and .16 for 200-d weaning weight (WWT), .16 and .43 for average daily gain (ADG), .19 and .31 for intake per day (MEI), .43 and .45 for yearling weight (YWT), .07 and .23 for RFC, .08 and .35 for FE, and .14 and .28 for NFE. Genetic and phenotypic correlations between MEI and ADG, MEI and YWT, ADG and YWT, ADG and FE, YWT and FE, and FE and NFE were moderately to highly positive for both breeds. Negative genetic and phenotypic correlations between NFE and ADG show partial correlations of FE with ADG after accounting for energy requirement for maintenance. Residual feed consumption was negatively associated with YWT, FE, and NFE, indicating a possible genetic improvement.

Genetic and phenotypic parameters among nine body dimensions and two measures of growth rate were estimated from measurements on 709 Angus and Hereford bulls and heifers born in 1984 and 1985. Height and width at hips, height at withers, body length, girth, head length and width, muzzle width, and cannon bone circumference were measured at weaning and again after 168-d postweaning gain tests. The cattle were from the final two calf crops of a 20-yr study to examine the response to selection for postweaning gain when fed either a high-concentrate diet or an all-hay diet. Sources of variation included year of birth, breed, sire within breed, diet, age of dam, and the linear regression on calf age. Parameter estimates among the body dimensions and carcass measurements were also calculated using a subsample of 318 Hereford and Angus bulls fed until they achieved > or = 7 mm of subcutaneous fat. Yearling measurements from calves fed the high-concentrate diet were larger than those from calves fed the all-hay diet. Sire within breed, age of dam, and the regression on age of calf affected all measurements (P < .001) at both measurement times. Dietary energy concentration influenced all body measurements taken at the end of test. Heritabilities of all body measurements were moderate to high. The highest genetic correlations with gain were for cannon bone circumference, body length, and heart girth. The heritabilities of all body dimensions were sufficient to indicate that selection progress was possible, but the low genetic correlations with gain and carcass traits suggested that this may not be desirable.

, W. M. 1997. Effect of feeding barley based diets on animal performance, carcass characteristics and meat quality of crossbred beef cattle with and without Wagyu genetics. Can. J. Anim. Sci. 77: 655-662. Growth performance, carcass characteristics and meat quality of European and British crossbred (EBC; no Wagyu genetics; 28 heifers and 30 steers) cattle were compared with crossbred cattle with 75% Wagyu genetics (WC; seven heifers and 14 steers) to determine the influence of Wagyu genetics on marbling grade of beef cattle fed barley-based diets in a factorial design experiment. Weaned calves (250 d average age) were fed, one of two diets (diet 1, 35% barley grain; diet 2, 40% hay cubes on DM basis, with barley silage, protein and vitamin/mineral premix) for 84 d and then fed diet 1 until they weighed 394 to 432 kg. All cattle were finished on an 80% (DM basis) rolled barley diet and slaughtered. Carcasses were graded and samples procured for meat quality and Warner-Bratzler shear force determination. Number of days on backgrounding diets to arrive at target weight (380 kg) was greater (P < 0.05) for the WC cattle, owing to relatively lower ADG, but days on the finishing diet were fewer for these cattle, compared with EBC cattle. Warm carcass yield (dressing percent) was greater (P < 0.05), but backfat depth was lower (P < 0.05) for WC cattle relative to that of EBC cattle, yet proportion of lean meat yield was similar. Eighty three percent of WC cattle carcasses had Canada AAA (small or more) marbling grade compared with 13% for EBC cattle carcasses. Mean shear force of meat samples from EBC and WC cattle was 4.2 and 3.8 kg, respectively. Results indicated that the extent of carcass marbling can be increased by incorporating Wagyu genetics but age at slaughter of WC cattle was 19 d greater than that of EBC cattle and carcass size was reduced. For personal use only. CANADIAN JOURNAL OF ANIMAL SCIENCEAlthough reported correlation coefficients among marbling fat, tenderness and organoleptic appeal of meat are not substantial (Wheeler et al. 1994), they are of sufficient magnitude, that the retail and food service industries specify minimal levels of intramuscular fat when purchasing cuts of meat. In Canada, approximately 20-25% of carcasses have marbling scores qualifying them for the Canada AAA grade. The frequency of carcasses which grade AAA or better for marbling needs to be increased to 50% to meet the requirement of current domestic and export markets (Jones et al. 1991;Jones 1996). In order to enhance the percentage of carcasses that grade Canada AAA, the use of Wagyu genetics requires consideration because the Wagyu beef cattle are acclaimed for their ability to deposit large amount of intramuscular fat .Inclusion of the Japanese American Wagyu in breeding programs has been described as a strategy to improve the marbling potential of beef carcasses (Barker et al. 1995). Lunt et al. (1993) compared growth rate and carcass characteristics of Angus and American Wagyu cattle and found that Wagyu steers exhibi...

Longissimus muscle area and fat thickness were measured following weaning, at yearling, and prior to harvest using real-time ultrasound, and corresponding carcass measurements were recorded 3 to 7 d following the preharvest scan in composite steers (n = 116, 447 +/- 19 d), bulls (n = 224, 521 +/- 11 d), and heifers (n = 257,532 +/- 12 d). Although fat deposition was limited in bulls and heifers from weaning to yearling, coefficients of variation ranged from 8.46 to 13.46% for muscle area, and from 27.55 to 38.95% for fat thickness, indicating that significant phenotypic variance exists across genders. Residual correlations, adjusted for the effects of year of birth, gender, and age at measurement, were high and ranged from 0.79 to 0.87 among ultrasound and carcass measures of muscle area. Residual correlations among ultrasound and carcass measures of fat thickness were also high, ranging from 0.64 to 0.86. Weaning and/or yearling ultrasound muscle area yielded similarly accurate predictions of carcass muscle area. Yearling ultrasound fat thickness accounted for 13% more of the observed variance in carcass fat thickness than the weaning ultrasound measure in single-trait prediction models. When both weaning and yearling ultrasound measures were used to predict carcass fat thickness, partial R2 values were 0.15 and 0.61 for weaning and yearling ultrasound fat thickness, respectively. The difference between predicted and carcass measures with respect to muscle area (fat thickness) was less than 6.45 cm2 (2.5 mm) for 80.2 to 88.9% (90.3 to 95%) of animals. Preharvest ultrasound measures yielded standard errors of prediction of less than 4.95 cm2 for muscle area and 1.51 mm or less for fat thickness. These results indicate that ultrasound measures taken between weaning and yearling provide accurate predictors of corresponding carcass traits in steers, bulls, and heifers.

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