Authors : M.A. Dominguez, A. Villanueva-Castillo, M.P. Ponce-Acosta, R. Castillo-Almaguer, E. Gutierrez-Rodriguez, O. Medellin-Avila, R. Lopez-Zavala and J. Salinas-Chavira
Abstract: Beef cows were evaluated from 6.5±1.6 months of gestation until 4 months postpartum, to correlate postpartum ovarian activity with body characteristics. Cows with Body Condition Score (BCS) of 4 or 5 (9-point scale) were sorted into three groups (n = 7 each): High-High (H/H), fed to maintain adequate BCS; High-Low (H/L), adequately fed prepartum but restricted (80% of nutritional requirements) postpartum and Low-High (L/H), restricted before calving but overfed afterwards (80 and 120%, respectively). Body composition (Backfat and rib eye area), fetal and calf development were evaluated every 14 days using ultrasound; weight and BCS were also measured. Despite ration differences, body composition and fetal measurements were similar among groups. Group L/H exhibited lower body weight and BCS (p<0.001) and calf birth weight (p<0.05) than H/H and H/L. Postpartum ovarian function was similar among groups. However, cows with average postpartum BCS scores ≥4 showed larger maximum follicle diameters than those with <4 (p<0.001). After temporary weaning at 60-90 days postpartum, only four cows ovulated. In conclusion, cows’ BCS affects fetal and early calf development, maximum follicle diameter and estrous cycle onset. Follicle waves of increasing diameter are present but adequate body condition is required to reach ovulation.
M.A. Dominguez, A. Villanueva-Castillo, M.P. Ponce-Acosta, R. Castillo-Almaguer, E. Gutierrez-Rodriguez, O. Medellin-Avila, R. Lopez-Zavala and J. Salinas-Chavira, 2011. Effects of Body Condition and Composition on the Onset of Postpartum Ovarian Activity in Beef Cows. Journal of Animal and Veterinary Advances, 10: 3236-3243.