Body mass index at calving on performance and efficiency of Zebu cow herds

This study examines the impact of the body mass index (BMI) at calving on the development and postpartum efficiency of cows of Zebu origin. The study involved 87 cows and their calves [pure Nellore (N) or predominant Nellore composition in a cross with Charolais (C) (3/4N1/4C and 5/8N3/8C)]. The mothers were grouped into classes according to their BMI at calving, namely, ‘small’, ‘moderate’ and ‘large’. Body mass index was determined by dividing the body weight of the cows by their length and by hip height and then dividing the result by 10. Cows were weighed at calving, at weaning, at the end of the breeding period and at the diagnosis of pregnancy. Calves were weighed at birth, at early weaning (63 days) and at 210 of age. To evaluate milk yield and quality, milk was collected at 21, 42 and 63 days after calving. Milk yield was measured by the direct method, with manual milking, followed by analysis of the lactose, fat, total solids and crude protein contents. Pregnancy rate was similar between the three BMI groups; however, cows with a lower BMI were more efficient at calving in producing kilograms of calf per kilogram of cow kept. Higher BMI provide higher milk yields, without affecting its quality, as well as heavier calves at early weaning and at 210 days of age.