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Evaluation of Calf Growth Patterns and Carcass Traits of Bos Indicus-Bos Taurus Steers
Abstract
Nellore-Angus steers (N = 572) born in 2009-2013, 2015, and 2019 and Brahman-Angus reciprocal steers (N = 73) born in 2019 and 2020 were evaluated for calf weights and carcass weights (HCW). Calves were born and reared at the McGregor Research Center and included F2, F3, F4, and F5 Nellore-Angus and F1 Brahman-Angus. Calves were weighed at 4 times: within 48 h of birth (BWT), 47 d age (spring-work weight, SWWT), 182 d age (pre-weaning weight, PRWWT), and 212 d age (weaning weight, WWT). Cow age category did not affect calf BWT or SWWT, but influenced PRWWT (P = 0.006) and WWT (P < 0.001); cow age category did not affect calf ADG. Brahman-sired F1 (B × A) males were 12.7 to 14.1 kg heavier for BWT (P < 0.001) and 14.9 to 19.2 kg heavier for SWWT (P < 0.001) than Angus-sired F1 males (A × B), but persistence of this difference to weaning varied across year. The correlations between calf traits and HCW were inconsistent across genetic types. No calf weight was correlated with HCW in A × B crosses, whereas PRWWT was in B × A crosses (r = 0.44, P = 0.007). BWT showed small to moderate correlation to HCW (0.23 < r < 0.46) in Nellore-Angus crosses; however, subsequent weights (SWWT, PRWWT and WWT) had large correlations with HCW (0.50 < r < 0.79) in the F4 and F5 calves, whereas these correlations varied from 0.24 to 0.37 in F2 and F3 steers. Animals of similar Bos indicus percentage may have quite different calf growth patterns related to HCW. The R2 value for carcass weight based on genetic type, year, and linear regression on harvest age was 0.29; however, the R2 was 0.96 based on genetic type and nonlinear regression of age across multiple calf weights. Multiple carcass traits were predicted with R2 values greater than 0.91 using multiple calf weights beginning at birth and their associated ages. Nonlinear age consideration from birth to weaning appears to be significant for predicting carcass traits in Bos indicus-Bos taurus crosses.
Citation
Lake, Steven Gunari (2023). Evaluation of Calf Growth Patterns and Carcass Traits of Bos Indicus-Bos Taurus Steers. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /200137.