Effect of nutrient management on the maturation of the reproductive axis in somatotrophic onset of puberty in heifers Nellore

Author(s)

Delci de Deus Nepomuceno

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2012-12-10

Examining board members

Alexandre Vaz Pires; Telma Teresinha Berchielli; Juliano José de Resende Fernandes; Paulo Henrique Mazza Rodrigues; Roberto Sartori Filho

• Advisor: Alexandre Vaz Pires

Abstract

The aim of the present study was to evaluate the effect of protein nutrition in the final third of gestation of Nelore cows, followed by supplementation strategies and / or feed their young females over the age of puberty until 18 months. The experimental design was a completely randomized factorial 2x2x2; constituting of: 2 suplementary managements of cows in pre-partum (Phase I); 2 supplementary managements of offspring (Phase II) and 2 alimentary managements during rearing (Phase IIIA). In Phase I, 241 cows were supplemented with soybean meal at the rate of 0.5 kg / cow / day (Treatment 1) and 258 cows were kept without access to supplemental Treatment 2 (control - phase I). About half of the cows and their female offspring, born in Phase I, were assigned to two treatments in Phase-II (supplementation of cubs) at 110 days of age of the offsprings, which now receive or not a mineral mix protein energy in creep-feeding, constituting, treatments supplementation in calves creep-feeding (n = 119) and control group (without supplementation, n = 122) in Phase II until 205 days of age (weaning). In phase III A, half of each group of calves in phase II were managed in feedlots (n = 119) and the other half remained in the pasture (control group, n = 122), up to 320 days of age. In stage IIIB, all heifers were managed together and submitted to the pasture breeding season from 440 days to 560 days old. Supplementation systems of cows and calves during the growing period did not affect body weight, concentration of IGF-1 and percentage of mature weight of heifers at the beginning of the breeding season (P> 0.05). The management of heifers in the feedlot phase IIIA, increased the number of pubertal heifers (31.9% vs 13.9%, P <0.01) for heifers fed in confinement or not, respectively. However, feeding in confinement caused no difference in age they reached puberty. Considering only heifers reached puberty (n = 55) there was an interaction effect between phases of supplementation / nutrition and age at puberty (P <0.05). For cows managed in Phase I, supplementation influenced the cyclicality of the same at the time of TAI (68.9% vs 55.4%, P <0.05), but caused no difference in the number of pregnant cows (60.1 vs 55.3%, P> 0.05), supplemented and nonsupplemented cows, respectively. Similarly, the addition of heifers in creep-feeding did not influence the rate of pregnancy in cows (P> 0.05). In conclusion, supplementation of cows with protein sources did not influence the age at puberty in heifers up to 18 months, and feeding management in confinement increased the number of pubertal compared with those managed on pasture. (AU)

• FAPESP's process: 09/17281-7 - Effect of nutritional management on fetal programming and maturation of the reproductive (hipotâmico - pituitary - varian)somatotrophic axis and its relationship with the onset of puberty early in Nellore heifers
• Grantee: Delci de Deus Nepomuceno
• Support Opportunities: Scholarships in Brazil - Doctorate