Describing variation in carcass quality traits of crossbred cattle.

In order to investigate variation in carcass quality traits, during a four-year period, mature Hereford cows (637) were mated to 97 sires from seven breeds (Jersey, Wagyu, Angus, Hereford, South Devon, Limousin and Belgian Blue), resulting in 1144 calves. Carcass production traits (carcass weight = HCWt, fat depth = P8, eye muscle area = EMA, intramuscular fat = IMF) were obtained from these cattle that constitute the Australia's Southern Crossbreeding Project. Data were analysed using multi-variate sire model containing fixed effects of sex, sire breed, slaughter age nested within sexes. Random effects were sire, dam, management (location-year-post-weaning groups) and environmental effects. HCWt of South Devon, Belgian Blue, Limousin and unexpectedly, Angus were the heaviest on the average. Hereford calves were intermediate and Jersey and Wagyu were lighter on the average than others. Carcasses of the Belgian Blue and Limousin had low P8 and IMF, carcasses of Hereford and South Devon were intermediate and Angus, Jersey and Wagyu had high P8 and IMF. Management group effects were greatest especially for EMA and IMF. The sire variation was about 6, 6, 4 and 2% of total variation for HCWt, P8, EMA and IMF. Heritability ranged from 0.20 to 0.37 (carcass weight). The genetic correlation between the two fat depots was not as high (0.18) as expected. Results from this study suggest that strategies to increase genetic potential for HCWt would increase the genetic potential for EMA but may reduce marbling and tend to slightly increase P8. All phenotypic correlations were positive, although not large.

Describing variation in rump P8 fat depth of crossbred cattle from birth to slaughter.

A Principal Component Analysis (PCA) was conducted on the matrix of correlations among P8 fat measures at seven different ages for steers and heifers. The P8 fat measures were collected from 1143 steers and heifer calves that were born to Hereford (h) dams inseminated with semen from seven different sire breeds: Angus, Belgian Blue, Hereford, Jersey, Limousin, South Devon and Wagyu, over a 4-year period (1994 to 1997). The first two principal components explained 61 and 57% of the total phenotypic variation in fatness for steers and heifers, respectively. The first component was positively correlated to all measures and was interpreted as a measure of overall fatness. The second component was positively correlated to fatness approximately pre-weaning and negatively correlated thereafter and thus was interpreted as maturity type but could be a function of milk supply. When estimated from a sire model, the heritability estimates were high for the first component (0.59 and 0.67 for steers and heifers, respectively) but low for the second component (0.05 and 0.19). The results demonstrate the value of combining information across multiple measurements to build accuracy, even when relatively crude methods are used.

Breed variation and genetic parameters for growth and body development in diverse beef cattle genotypes.

Conformation scores can account for more than 20% of cattle price variation at Australian livestock sales. However, there are limited available references which define genetic factors relating objective live developmental traits to carcass composition. Weaning and post-weaning weight, height, length, girth, muscle (ratio of stifle to hip width) and fat depth of 1202 progeny from mature Hereford cows (637) mated to seven sire breeds (Jersey, Wagyu, Angus, Hereford, South Devon, Limousin and Belgian Blue) were examined for growth and development across ages. Crossbred Wagyu and Jersey were both lighter in weight and smaller in size (height, length and girth) than purebred Hereford and crossbred Angus, South Devon, Limousin and Belgian Blue. Within the five larger crossbreds, there were significant changes in relative weight from weaning to 600 days. Sire breeds differed in fat depth, with Angus being the fattest (9% on average fatter than Hereford and Wagyu), and Jersey 5% less fat than Hereford, followed by South Devon and Limousin (19% lower than Hereford) and Belgian Blue (39% lower than Hereford). Direct heritability ranged from 19 to 42% and was higher than the proportion of total phenotypic variance accounted for by maternal effects (which ranged from 0 to 17%) for most body measurement traits except for weight (38 v. 18%) and girth (36 v. 9%) traits at weaning, an indication of maternal effect on some body conformation traits at early ages. Muscularity (19 to 44%) and fat depth (26 to 43%) were moderately to highly heritable across ages. There were large differences for growth and the objective measures of body development between crossbreds with a degree of overlap among the progeny of the seven sire breeds. The variation between genetic (positive) and environmental (negative) correlations for dry versus wet season average daily gains in weight and fat, suggested the potential use of live-animal conformation traits for within breed selection of genetically superior animal in these traits across seasons.

Differences in delta9 desaturase activity between Jersey- and Limousin-sired cattle.

An experiment examined delta9 desaturase activity and FA composition in subcutaneous adipose tissue in two differing breeds of cattle. Jersey-sired cattle had significantly higher rates of desaturase activity than Limousin-sired cattle (1.55 vs. 0.75 nmol/mg protein/min). This difference was also demonstrated by a lower concentration of individual (e.g., 18:0) and total saturated FA (38.3 vs. 45.1 wt%), and a higher concentration of individual (e.g., 16:1) and total monounsaturated FA (58.2 vs. 52.7 wt%) in the Jersey animals. Other indices of desaturation calculated from the FA composition showed this same difference. The slip point of adipose tissue of Jersey cattle (36.8 degrees C) was significantly lower than that of Limousin cattle (39.2 degrees C), but Jersey adipose tissue had a greater content of beta-carotene. The positive relationship between adipose tissue beta-carotene and desaturation opposes the negative relationship between dietary beta-carotene and desaturation determined elsewhere. These results, however, lead to the hypothesis that some cattle have a reduced capacity to metabolize beta-carotene to various forms of vitamin A, a compound that can reduce delta9 desaturase enzyme activity. In addition, the higher level of intramuscular fat in Jersey cattle (6.97 vs. 3.82%) is possibly related to a lack of inhibition of the adipocyte differentiation genes by vitamin A.

Genetic variation in fatness and fatty acid composition of crossbred cattle.

Mature Hereford cows (766) were mated to 97 sires from seven breeds (Jersey, Wagyu, Angus, Hereford, South Devon, Limousin, and Belgian Blue), resulting in 1,215 calves born over 4 yr (1994 to 1997). These cattle comprised Australia's 'Southern Crossbreeding Project." Heifers were slaughtered at an average of 16 mo with hot standard carcass weight of 219 kg and 9 mm fat over the rump. Steers were slaughtered at an average of 23 mo with carcass weight of 319 kg and 13 mm fat over the rump. Meat and fat samples were taken from the carcass on the day after slaughter for subsequent laboratory analysis of i.m. fat content and fatty acid composition. Data were analyzed using uni- and bivariate animal models containing fixed effects of cohort, management group, birth month, and sire breed. March-born calves had fat with a 0.5 degrees C lower melting point, 0.6% higher total monounsaturated fatty acids, and 0.7% higher fatty acid desaturation index than calves born in April. Steers born in 1997 were the only cohort finished on pasture, and they had much more yellow fat than the other cohorts. Four heavy breed crosses (Angus, South Devon, Limousin, and Belgian Blue) averaged 284 kg carcass weight, followed by purebred Hereford (268 kg), Wagyu (244 kg) and Jersey (236 kg). Angus had the greatest fat depth (14.3 mm), ahead of Hereford and Wagyu (11.9 mm), Jersey (10.7 mm), South Devon and Limousin (9.9 mm) and Belgian Blue (8.0 mm). Jersey, Wagyu, and Angus had themost i.m. fat (4.6%), followed by Hereford and South Devon (3.8%), and Limousin and Belgian Blue (3.1%). The highly marbled Jersey and Wagyu had softer fat (6% lower fat melting point) than the other breeds. Angus were more highly marbled, similar to Jersey and Wagyu, but had harder fat similar to the leaner breeds. Heritabilities for all traits were low to moderate (16 to 36%). Genetic correlations between fatty add composition and carcass traits were not significant, indicating little evidence of antagonisms between traits that would prevent genetic progress in both production and quality.

Use of orally administered oxidised copper wire particles for copper therapy in cattle.

Oxidised copper wire particles (OCWP) were given per os to cattle as an alternative to subcutaneous copper glycinate injections. OCWP were recovered from the stomachs of cattle slaughtered 3 months after treatment. OCWP (50g) treatment resulted in sustained higher plasma copper concentrations than subcutaneous injections of copper glycinate. OCWP given at high doses (300g) raised liver copper concentrations to 16 mmol/kg without clinical effects. It is concluded that OCWP could be a practical alternative to current injection methods of copper therapy.

Copper administration to young calves: oral dosing with copper oxide compared with subcutaneous copper glycinate injection.

Calves were dosed with 50 g of copper oxide granules orally or given 120 mg copper glycinate subcutaneously. There was no significant difference between the weights of calves given either treatment during the trial. However, the copper oxide treatment resulted in sustained higher concentration of plasma copper and higher liver reserves than the glycinate treatment.