RESUMO
El objetivo de esta revisión es describir el efecto de estrategias nutricionales y de manejo sobre la condición corporal y el desempeño reproductivo de vacas de carne. Las vacas de carne experimentan un balance energético negativo durante el postparto, perdiendo condición corporal. El desarrollo folicular, la tasa de preñez, la fertilidad, los intervalos parto-primer estro, parto-concepción e intervalo entre partos son superiores en vacas con condición corporal moderada durante el postparto, comparadas con vacas delgadas. La suplementación con lípidos de cadena larga poliinsaturados permite obtener una reanudación de la ciclicidad ovárica temprana, independiente de su contribución energética. La suplementación con proteína ayuda a mantener o mejorar la condición corporal durante el postparto, optimiza el medio ambiente ruminal y la eficiencia digestiva de los animales. El destete precoz y el amamantamiento restringido se han venido utilizando en sistemas de cría extensivos, ya que la aplicación de este tipo de estrategias es relativamente fácil. Estas actividades tienen efecto sobre el eje hipotálamo-hipófisis-ovario y reducen los requerimientos energéticos de la madre derivados de la producción de leche, permitiendo mejorar la condición corporal y la reiniciación de la actividad ovárica, además de optimizar los resultados de tratamientos con progestágenos cuando son usados alternamente. En conclusión, una adecuada condición corporal postparto es esencial para garantizar el rendimiento reproductivo de vacas de carne. El uso de suplementación con lípidos y proteína durante el postparto mejora la condición corporal y optimiza el rendimiento reproductivo de vacas de carne. Estrategias de manejo como el destete precoz son efectivas, pero su uso se restringe solo cuando las fuentes nutricionales son escasas o la aplicación de estrategias nutricionales no es posible.
The aim of this review is to describe the effect of nutritional and management strategies on body condition and postpartum reproductive and productive performance in beef cattle. Beef cattle experience a negative energy balance during postpartum, losing body condition. Follicular development, pregnancy rate, fertility, intervals from labor-first estrus, labor-conception and labor interval are superior in cows with moderate body condition during postpartum compared to thin cows. Supplementation with long chain polyunsaturated lipids, allows earlier resumption of ovarian cyclicity, regardless their energetic contribution. Protein supplementation helps to maintain or improve body condition during postpartum, maximizing the ruminal environment and animal digestive efficiency. Early weaning and restricted sucking have been used in extensive breeding systems, since the implementation of such strategies is relatively easy. These activities have effects on the hypothalamic-pituitary-ovarian and reduce milk production thus allowing the improvement of body condition and the restarting of ovarian activity, also optimizing the results of treatments with progestogens when they are used alternately. In conclusion, appropriate postpartum body condition is essential in order to ensure the reproductive performance of beef cattle. The use of lipid and protein supplementation during postpartum improves body condition and optimizes the reproductive performance of beef cattle. Management strategies such as early weaning are effective, but their use is restricted only when nutritional sources are scarce or the application of nutritional strategies is not possible.
RESUMO
The present work was sponsored by the covenant SAA/IZ/UNITAU, and carried out at Estação Experimental de Zootecnia de Pindamonhangaba, SP. It was used, for the disappearence study in situ, dracon bags placed on a rumen fistulated bovine. The disappearence determination of dry mattter (DM), organic matter (OM), and crude fiber (CF), was conducted with bags removed at intervals of 2, 4, 6, 12, 24 and 48h. For DM and OM the represented equations which describe rumen digestion showed a similar disappearence, however it occurred a faster disappearence for CF considering the same experimental conditions. The estimation of rumen CP degradability was measured by the equation p= a+ b (l-e-ct); considering different turnover rates (k). The results obtained for k= 0.02; 0.05 and 0.08; were respectively: 81.39, 64.54 and 54.43% of CP degradability.
O experimento foi realizado através do convênio SAA/IZ/UNITAU, e desenvolvido na Estação Experimental de Zootecnia de Pindamonhangaba, SP. Os estudos, in situ, foram realizados com sacos de dracon, em bovino fistulado no rúmen. Avaliou-se o desaparecimento da matéria seca (MS), matéria orgânica (MO) e fibra bruta (FB), após 2,4,6,12, 24 e 48 horas de incubação. As equações obtidas apontam um grau semelhante de desaparecimento de MS e MO do substrato dos sacos de dracon. Entretanto, quanto à fração FB, ocorreu um comportamento diferenciado, mostrando um desaparecimento mais rápido, em função do tempo de incubação. A curva de degradabilidade protéica no rúmen foi ajustada de acordo com a equação geral p= a+ b (l-e-ct), assumindo diferentes taxas de passagem (k). Os resultados obtidos foram de 81,39; 64,54 e 54,43%de degradabilidade, respectivamente para k= 0,02;0,05 e 0,08.
RESUMO
The present work was sponsored by the covenant SAA/IZ/UNITAU, and carried out at Estação Experimental de Zootecnia de Pindamonhangaba, SP. It was used, for the disappearence study in situ, dracon bags placed on a rumen fistulated bovine. The disappearence determination of dry mattter (DM), organic matter (OM), and crude fiber (CF), was conducted with bags removed at intervals of 2, 4, 6, 12, 24 and 48h. For DM and OM the represented equations which describe rumen digestion showed a similar disappearence, however it occurred a faster disappearence for CF considering the same experimental conditions. The estimation of rumen CP degradability was measured by the equation p= a+ b (l-e-ct); considering different turnover rates (k). The results obtained for k= 0.02; 0.05 and 0.08; were respectively: 81.39, 64.54 and 54.43% of CP degradability.
O experimento foi realizado através do convênio SAA/IZ/UNITAU, e desenvolvido na Estação Experimental de Zootecnia de Pindamonhangaba, SP. Os estudos, in situ, foram realizados com sacos de dracon, em bovino fistulado no rúmen. Avaliou-se o desaparecimento da matéria seca (MS), matéria orgânica (MO) e fibra bruta (FB), após 2,4,6,12, 24 e 48 horas de incubação. As equações obtidas apontam um grau semelhante de desaparecimento de MS e MO do substrato dos sacos de dracon. Entretanto, quanto à fração FB, ocorreu um comportamento diferenciado, mostrando um desaparecimento mais rápido, em função do tempo de incubação. A curva de degradabilidade protéica no rúmen foi ajustada de acordo com a equação geral p= a+ b (l-e-ct), assumindo diferentes taxas de passagem (k). Os resultados obtidos foram de 81,39; 64,54 e 54,43%de degradabilidade, respectivamente para k= 0,02;0,05 e 0,08.