070 The influence of age at first calving on productivity of Brahman females

We hypothesized that age at first calving affects the productivity of Brahman cows. The objective of this study was to determine the effect of age at first calving on productivity of Brahman cows. Calving and weaning records (180 d Adj WW) of Brahman cows (n=175) born from 2005 to 2010 and exposed, as yearlings, to fertile bulls continuously until pregnancy were analyzed, cows that failed to conceive in two subsequent breeding seasons were removed. Cows that calved by 800 d of age were defined as early maturing (EM). Cows that calved between 801 and 900 d of age were intermediate (IM) and cows that calved at >900 d of age were late maturing (LM). The data were analyzed by PROC CORR and PROC MIX of SAS. Age at first calving was correlated (r=0.43; P<0.001) with age at 4th calving and with the cumulative kg of calf weaned by 5 yr of age (r-0.21, P<0.05). The number of calves weaned by 5 yr of age was negatively correlated (r=-0.31; P<0.001) with age at 1st calving and positively correlated with cumulative kg of calf weaned by 5 yr of age (r=0.91; P<0.001). Age at 4th calving did not differ between LM (2303.64±29.20 d) and IM (2206.05±39.79 d) but both were significantly older (P<0.05) than EM (2028.58±37.22 d) cows. The interval between the 1st and 2nd calving was similar (P<0.05) for the EM (491.94±16.46 d) and LM cows (460.08±12.01 d), but was greater (P<0.05) in IM cows (553.53±19.76 d). The calving interval between the 3th and 4th calving did not differ among groups. At 5 yr of age the cumulative kg of weaned calf per cow was significantly greater (P<0.05) in EM (537.48±20.18 kg) than in LM cows (455.47±13.95 kg). These results demonstrate that Brahman cows that calve at 2 yr of age are more productive than LM because they were younger at their 4thcalving and by 5 yr of age they weaned more kg of calf. Mean and SE of the age (d) at calving the 2nd; 3rd and 4th offspring. a;b;c = P<0.05 differences by column