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 (P₄) 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 P₄ 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.

在80个Girolando小母牛中确定了饲料补充剂（FS）对青春期的年龄和体重，卵巢滤泡种群和血液中的孕酮浓度的影响。小母牛分布在四种处理中：T1）接受FS的8个月大的小母牛（n  = 20）；T2）8个月大的小母牛没有FS（n  = 20）；T3）10个月大的小母牛接受了FS（n  = 20）；和T4）10个月大的小母牛没有获得FS（n = 20）。在研究开始时，然后每21天记录一次体重。然后确定每日体重增加，总体重增加和青春期体重。T1和T3的小母牛每天接受2千克饲料补充，直到青春期开始。经直肠超声检查卵巢结构，以确定中等大小（4.1–8 mm）和大大小（≥8.1mm）的卵泡，显性卵泡的生长，排卵并确认黄体（CL）的存在。使用固相酶联免疫吸附测定（ELISA）在排卵后第7天和第14天确定血中孕酮（P ₄）的浓度。饲料补充的小母牛较早达到青春期且体重较重。卵泡人口，优势卵泡生长和血液P给予FS的小母牛中_4个浓度更高（P < 0.05）。在两个年龄组中，补充饲料都能使小母牛的青春期降低4到5个月。总之，应在10岁而不是8个月大时给小母牛提供FS，因为这样可以将FS期间的持续时间缩短2个月。