Genetic evaluation of postweaning performance traits in Brahman and Brahman-influenced stockers grazing rye-ryegrass or bermudagrass pastures

Growth of young cattle on forages and pastures has a major effect on the profitability of the stocker cattle industry. The objectives of this study were to estimate heritability of performance traits and additive genetic correlations of pairs of traits in Brahman and Brahman-influenced (0.25 or 0.5 Brahman) stocker cattle on rye (Secale cereale) + ryegrass (Lolium multiflorum) (RRG; n = 2,031) or bermudagrass [Cynodon dactylon (L.) Pers.] (BER; n = 1,322). Data from 1986 to 2014 at Overton, Texas, for BW, ADG, and BCS were analyzed for each stocking season. Main effects included stocking rate (3 levels), proportion of Brahman inheritance (3 levels on RRG: 0.25, 0.5, 1; 2 levels on BER: 0.25 and 1), supplementation status, and contemporary groups. Stockers receiving supplement were heavier (P < 0.001) from both RRG (365.3 ± 4.2 kg) and BER (363.8 ± 3.0 kg) compared with nonsupplemented stockers (348.1 ± 2.5 and 343.9 ± 2.7 kg, respectively). Within each breed group, BW and ADG means were greater (P < 0.003) for low stocking rates. Heritability estimates for BW and ADG were 0.56 ± 0.05 and 0.1 ± 0.06, respectively, on RRG. Estimates of additive genetic and phenotypic correlations were 0.69 ± 0.13 and 0.59 ± 0.02, respectively. Heritability estimates for BW, ADG, and BCS of stockers on BER were 0.5 ± 0.1, 0.11 ± 0.09, and 0.27 ± 0.1, respectively. Additive genetic correlation of BW and BCS during BER was large (0.61 ± 0.17), but estimates for the other pairs of traits did not differ from zero.