Evaluation of Bos indicus and Bos taurus straightbreds and crosses. I. Post-weaning growth of steers in different environments

Abstract

Post-weaning growth of 186 steers comprizing straightbred Hereford (H x H) and Brahman (B x B), first-cross (B x H) and back-cross (H x BH and B x BH) was evaluated. The steers had been raised to weaning (8 months of age) by dams which grazed either high, medium or low quality pasture (pre-weaning pasture system) at Grafton, N.S.W. The steers were grown on pasture from time of weaning in one of three locations in New South Wales representing subtropical, temperate-good, and temperate-good to poor environments, and slaughtered when the average fat cover of the back-cross steers in each environment was 4-10 mm at the 12113th rib. Pre-weaning pasture system had a significant effect on post-weaning growth, with mean post-weaning (8-48 months of age) average daily gain (ADG) of steers from low (327� 8 g/day) being higher than that of steers from medium (304�6 g/day), which in turn, was higher than that of steers from high (276�9 g/day) quality pre-weaning pasture, indicating that steers from low and medium quality pastures exhibited compensatory growth. From 8 to 24 months of age, first-cross BxH steers had the highest ADG in all environments. The ranking of the other genotypes differed across environments. In the environment where growth rate was lowest (178 g/day for B x H), B x B and B x BH steers grew faster than H x H and H x BH steers; where growth rate was highest (584 g/day for B x H), the order was reversed; and where growth rate was intermediate (323 g/day for B x H), there were no significant differences in ADG among H x H, H x BH, B x BH and B x B steers. Steers from only two environments were retained after 24 months of age. Mean ADG from 8 to 36 or 48 months of age was not significantly different among straightbred and back-cross steers, but was lower than that for the first-cross steers. Genotype x environment interaction for liveweight at slaughter was not significant. First-cross B x H steers were 56 kg (11%) heavier (P < 0.05) than back-cross steers, which in turn, were 37 kg (8%) heavier (P < 0.05) than straightbred steers at slaughter.

Genetics of steer daily and residual feed intake in two tropical beef genotypes, and relationships among intake, body composition, growth and other post-weaning measures

“…Genotype · environment interactions commonly occur when breeds or breed-crosses are compared across variable environments (Thompson et al 1981;Darnell et al 1987;Arthur et al 1994), and in our study, they were indicated by the presence of significant genotype · cohort effects. The cohort mean level for a trait was taken as the measure of environment Estimates differed for Brahman and Tropical Composite; see Table 10 for genotype-specific estimates.…”

Compensatory growth in Belgian Blue bulls previously grazed at two stocking rates: animal performance and meat characteristics

“…Indeed, forage-based diets are known to decrease C18 :2 proportions in fat when compared with concentrate diets (Marmer et al, 1984). The high concentration of C18:3 in grass itself (Butler and Bailey, 1973) must be also implicated in this phenomenon (Dawson and Steen, 1997). This stemmed probably from the higher leaness of meat, leading to higher proportion of unsaturated lipid membranes in total meat fat (Leat, 1983), as suggested in Figure 3.…”