Feed supplementation affect age and weight at puberty in Girolando (Bos taurus x Bos indicus) heifers in the tropics

The effect of feed supplementation (FS) on age and weight at puberty, ovarian follicular population and blood progesterone concentrations was determined in 80 Girolando heifers. Heifers were distributed in four treatments: T1) 8-month-old heifers that received FS (n = 20); T2) 8-month-old heifers that received no FS (n = 20); T3) 10-month-old heifers that received FS (n = 20); and T4) 10-month-old heifers that received no FS (n = 20). Body weight was recorded at the beginning of the study and then every 21 days. Daily weight gain, total weight gain and weight at puberty were then determined. Heifers in T1 and T3 received each 2 kg of feed supplement daily until the onset of puberty. Ovarian structures were examined by transrectal ultrasonography to determine the population of medium size (4.1-8 mm) and large size (>= 8.1 mm) follicles, growth of dominant follicles, ovulation and to confirm the presence of a corpus luteum (CL). Blood progesterone (P-4) concentrations were determined on days 7 and 14 post-ovulation, using solid phase enzyme-linked immunosorbent assay (ELISA). Puberty was reached at an earlier age and heavier body weight in feed supplemented heifers. Follicular population, growth of the dominant follicle and blood P-4 concentrations were higher (P<0.05) in the heifers given FS. Feed supplementation reduced the age at puberty in heifers by 4 to 5 months in both age groups. In conclusion, FS should be offered to heifers at 10 instead of 8 months of age, because this will shorten by 2 months the duration of the FS period.