Senepol Symposium, St

The objective of this study was to determine the growth patterns and performance ofFI Brahman (Bos indicus)-, Senepol (Bos taurus)-, and Tuli (Sanga)-Angus calves under semiarid south Texas conditions. Four hundred eighty-nine preweaning records collected over 4 yr were analyzed. The statistical model for performance traits included the effects of breed of sire, year, sex, age of dam, and breed of sire x year. Year effects were important (P < 0.05) for performance traits but could be explained, at least partially, by differences between years in rainfall patterns. Brahman Fl calves were 13% less (P < 0.05) vigorous at birth, 4.7 kg heavier (P < 0.05) at birth, 13.5 kg heavier (P < 0.05) at weaning, 0.25 units lower (P < 0.05) in body condition score (BCS) at weaning, and 1.75 units greater (P < 0.05) in frame score (scores of 1 to 9) at weaning than Tuli and Senepol Fl calves. Senepol Fl calves were intermediate (P < 0.05) between the Brahman and Tuli Fl calves for birth and weaning weight, but had 11 % more (P < 0.05) vigor at birth than the other two crossbreds. Tuli and Senepol Fls were similar (P > 0.05) in BCS and frame size at weaning. Males were 3.3 kg heavier (P = 0.12) at birth than females, especially for the Fl Brahman males that were 4.5 kg heavier (P < 0.05) than their counterparts. Brahman Fls weaned 19.9 kg heavier (P < 0.05) than the average of the other two Fls in the year of the greatest rainfall (1994), whereas, the average advantage in other years was 11.4 kg. This difference gave rise to a breed of sire x year interaction (P < 0.003). Brahman Fls were heavier at every measurement both preweaning and postweaning, and appeared to be later maturing and more able to excel under good forage conditions than the other two Fl breed types; Senepol and Tuli Fls were similar (P > 0.05) in these respects, but appeared to be more competitive in relative preweaning growth rate to the Brahman Fl calves in years of greater nutritional stress. Because the Brahman Fl females had heavier (P < 0.05) weights throughout the experiment, but were later maturing, they had lower reproductive rates than the other two Fl breed types. Senepol and Tuli Fl 's were earlier maturing, but the Senepol Fl 's had difficulty calving as two year olds, reducing their percent calf crop weaned. As a result, the Tuli Fl's weaned more calf per female exposed, and more calfper 100 kg female exposed than the other Fl breed types. Senepol and Brahman Fl 's were similar in efficiency of production for their first calving opportunity. However, Senepol Fl females weaned less calfper 100 kg female maintained for both the second and third calving opportunities. The Tuli Fl females had the highest efficiency for their 1st and 2nd calving opportunities but were similar to Brahman Fl females by their 3rd calf. Brahman F 1 females had the highest weight of calf per loo kg cow maintained for their third calf.