Growth and reproductive performance in females of Romosinuano cattle

Objective. To characterize growth curves and reproductive performance of Romosinuano cows in Mexico. Materials and methods. Weightand age records (928)of females (117) for growth traits and calving records (459) of cows (113) for reproductive traits were analyzed. Four non-linear mixed models were adjusted to describe the growth curves. Indicators of age at 50% of maturity (A50M), and percentage of maturity at 18 months of age (PM18) were estimated. The reproductive performance was evaluated through the age at first calving (AFC), the calving interval (CI), and calving rate (CR). Results. The Brody model showed the best adjustment to the growth curve. The Aparameter, which estimates maturity weight, fluctuated within 430.2 and 466.2 kg; the b parameter within 0.94 and 5.45; and the kparameter within 0.001 and 0.002; depending on the used model. The A50M varied from 20 to 21 months, and the PM18 from 44.5 to 45.5%. The means for AFC, CI, and CR at 550 d were 1059±282 d, 553±68 d, and 74±19%; those indicators improved (p<0.05) when cows have a higher percentage of their maturity weight, depending on calving season. Conclusions. The estimates of maturity weight indicate that Romosinuano cattle could be considered as a breed of small or medium size, with an acceptable reproductive ability. The females with small estimated maturity size aged at first calving earlier than cows with high weights.