Strategic supplementation of grazing beef cows during gestation: effects on postpartum reproductive traits of the dams and skeletal muscle development of the progeny

• Ano de defesa: 2017
• Autor(a) principal: Contreras Marquez, David Esteban
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Bovino - Reprodução; Nutrição animal; Avaliação de Alimentos para Animais
• Link de acesso: http://www.locus.ufv.br/handle/123456789/11090

The present study was carried out with the objective of determining the effect of supplementation of Nelore matrices maintained in grazing during the different gestation periods on postpartum fertility and progeny performance up to 8 months old (weaning). Thus, 27 Nelore matrices were used, divided into three groups (n = 9 for each group) as follows: matrices not supplemented during gestation (UNS), matrices supplemented from 30 to 180 days of gestation (MID) and supplemented matrices of 181 to 281 days of gestation (LATE). The percentage composition of the supplements provided for the matrices was: ground corn (26.25%), wheat bran (26.25%) and soybean meal (47.5%). The supplement was formulated to contain 30% CP. 150 kg of supplement were provided per animal during each supplementation period (1 and 1.5 kg / day for cows in the MID and LATE groups, respectively), accompanied by a mineral blend offered ad libitum. UNS matrices received only mineral mixture ad libitum during gestation. Blood samples were taken to determine the concentrations of NEFA, BHBA (β- hydroxybutyrate) and glucose at days 30, 105, 180, 230 and 281 of gestation of the matrices. After delivery on days 10, 18 and 30, blood samples were taken to determine the progesterone concentration (P4), as well as ultrasonographic assessments to determine the size, absence of fluid in the uterine horns and presence of ovarian follicles and bodies luteous. Fixed-time artificial insemination (FTAI) was performed in all matings at 45 days postpartum and twenty-eight days after insemination, a diagnosis was made to determine the percentage of gestation. After birth, all progenies were supplemented for eight months until weaning, with the same supplement in equal amounts. The percentage composition of the supplement was: ground corn grain (30%), wheat bran (30%), soybean meal (35%) and molasses (5%). The supplement was formulated to contain 25% CP. The supplement was offered in an amount of 6 g / kg body weight, and the mineral blend was offered ad libitum. Thirty days postpartum were performed on progeny biopsy of skeletal muscle tissue to determine number, size of muscle fibers and expression of genetic markers. During the reproduction phase, the weight gain, the thickness of the subcutaneous fat and the loin eye area were evaluated in the progeny. A lower concentration of NEFA and BHBA (P <0.01) at 180 and 281 days of gestation was observed for MID and LATE matrices respectively. Higher glucose concentration (P <0.1) during pregnancy was observed for MID matrices at 180 days and LATE at 281 days of gestation. Involution of the uterus was observed at 30 days postpartum, with a size of 14.40 ± 1.31, 15.70 ± 1.20 and 14.70 ± 1.25 mm, respectively for the treatments UNS, MID and LATE. Progeny performance (P = 0.953) was not influenced by supplementation of the pregnant matrices; greater subcutaneous fat thickness (P = 0.006) was observed in the progeny of LATE matrices; there was larger loin eye area (P = 0.077) for progenies of MID and LATE matrices when compared to the UNS. A higher number of muscle fibers (P = 0.093) was observed for the progeny of the MID matrices when compared to the UNS, but no differences were observed in the LATE matrices and in the UNS matrices. No influence of supplementation of pregnant matrices on the size of the progeny muscle fibers (P = 0.208) was detected. A higher expression of FGF2 (P = 0.003) was observed for the progeny of the MID treatment. Higher PPARα expression (P = 0.073) was also observed for progenies of MID matrices when compared to LATE. Prepartum supplementation improves energy balance by increasing glucose concentration and decreasing the concentration of NEFA and BHBA, without altering uterine involution and postpartum fertility. Strategic supplementation of pregnant grazing matrices does not alter progeny performance during the breeding phase, but improves the expression of genetic markers (FGF2 e PPARα) capable of positively influencing fetal myogenesis and adipogenesis.