Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2003
Publication Date: 7/1/2003
Citation: Riley, D.G., Barling, K.S., Chase, C.C., Olson, T.A., Hammond, A.C., Coleman, S.W. 2003. Odds ratios for failure to calve and wean for Senepol- and Tuli-Angus cows compared to Brahman-Angus cows. Journal of Animal Science. 81(Suppl-1):254.
Technical Abstract: The objective of this study was to compare reproductive performance of F1 Senepol- and Tuli-Angus cows to that of F1 Brahman-Angus cows (bred to Charolais bulls) using calving (n = 640) and weaning (n = 633) records from 1996 to 2001. Traits evaluated were 1) failure to calve, and 2) failure to wean a calf. Cows failing to calve or to wean a calf in a given year were coded 1; otherwise they were coded 0. Traits were modeled as binomially-distributed using repeated measures, generalized estimating equations, and a logit link function to an assumed underlying normal distribution. Effects investigated included breed, year, cow age, cow birth year, and sire of cow. Clustering associated with cow age was modeled using repeated measures analysis with an unstructured covariance matrix. Odds ratios (OR) and 95% confidence intervals (CI) were generated to compare breeds. Cow breed, year, cow birth year, and breed H year interaction were highly significant in all analyses. Sire of cow (P > 0.25) was excluded from final models. Senepol F1s had significantly greater odds of failure to calve than Brahman F1s in 1997, 1998, 2000, and 2001, as indicated by OR (CI) of 1.87 (1.09, 3.2), 3.81 (1.01, 14.32), 2.88 (2.47, 3.36), and 11.69 (9.49, 14.4), respectively. Senepol F1s had greater odds of failure to wean a calf than Brahman F1s in 1997, 1998, 2000, and 2001, as indicated by OR (CI) of 2.29 (1.66, 3.16), 4.88 (1.2, 19.82), 2.81 (2.3, 3.42), and 9.18 (3.41, 24.71), respectively. In contrast, Tuli F1s were similar to Brahman F1s, but had lower odds of failure to calve (OR = 0.09; CI = 0.04, 0.2) or wean (OR = 0.19; CI = 0.06, 0.58) than Brahman F1s in 1999 and greater odds of failure to wean a calf than Brahman F1s in 2000 (OR = 2.64; CI = 2.22, 3.13). Results indicate that the Tuli breed may be a viable source of non-Zebu adaptation to the subtropics. Brahman, Senepol, Tuli