Influence of the nutritional plane and the racial predominance on the ovarian activity in pubescent crossbred heifers.

Abstract

In order to evaluate the effect of two nutrition planes and two racial predominance on the appearance of puberty and ovarian activity referring to follicular growth, development of the corpus luteum (CL) and determination of serum progesterone levels (P4), 36 Holstein (H = 18) and Brown Swiss (P = 18) crossbred heifers were used, with an average weight of 190 ± 10 kg and 10 months of age. The formulation of the nutrition plans (100 and 150%) was carried out according to the NRC, making consumption adjustments every 28 days based on live weight. Rectal palpations were performed fortnightly and serum P4 levels were determined weekly. Racial predominance did not influence weight at puberty (PP), but it did affect age at puberty (EP) (H = 18.0 vs. P = 20.6 months; P<.05). The PP was 284.7 and 263.8 kg and the EP was 18.0 and 20.7 months for the 150 and 100% planes, respectively. The onset of puberty, the presence of LC on palpation, and the size of the ovaries were affected by the level of feeding. A greater presence of CL was detected in the right ovary, influencing their larger size. The animals that did not detect CL or P4 levels higher than 0.5ng / ml, presented a smaller ovarian size. The NRC-100% feeding level resulted in a lower development and functionality of the ovaries and therefore a delay in the onset of puberty.