Impacto da oferta de forragem na recria de novilhas Nelore destinadas a reposição e tempo de confinamento das fêmeas vazias
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2021-07-21
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Universidade Estadual Paulista (Unesp)
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O estudo do manejo do pasto associado ao uso de alta suplementação [10 g/kg do peso corporal (PC)] é uma estratégia para reduzir a idade à reprodução de novilhas Nelore destinadas à reposição. Além disso, como forma de aproveitar as novilhas vazias oriundas desse sistema, o estudo do tempo de confinamento (TC) se faz necessário para o entendimento da dinâmica de deposição de carcaça e avaliação da eficiência alimentar desses animais. Nesse sentido foi realizado dois experimentos. No primeiro experimento (Exp. 1) foi avaliado o efeito de duas ofertas de forragem (OF; alta e baixa; AOF e BOF, respectivamente) sobre a estrutura do dossel, valor nutritivo da forragem, consumo de suplemento, desempenho, características de carcaça e índices reprodutivos durante a recria de novilhas Nelore recém desmamadas (7 ± 1 meses de idade), recebendo alta suplementação em pasto de capim-marandu {Brachiaria brizantha (Hochst. ex A. Rich.) R.D. Webster [syn. Urochloa brizantha Stapf cv. Marandu]}, sob lotação contínua, desafiadas à reprodução aos 14 meses de idade (protocolo de inseminação em tempo fixo). No segundo experimento (Exp. 2), avaliou-se o efeito de três TC (45, 75 e 105 dias) sobre o desempenho, características de carcaça, consumo e eficiência alimentar de novilhas Nelore vazias (16 ± 1 meses de idade), oriundas do Exp 1. No Exp. 1 observou-se que a manipulação da estrutura do dossel em duas OF afetou as características estruturais e nutricionais do pasto, sendo que o tratamento de AOF apresentou maior altura (P < 0,01), maior proporção de colmo verde (P < 0,01), menor proporção de folha verde (P = 0,080), menor teor de proteína bruta (PB; P < 0,01) e menor relação PB:digestibilidade in vitro da matéria seca (DIVMS; P < 0,01) em comparação ao tratamento de BOF. Não foi observado efeito das OF no consumo de suplemento (P = 0,117), mas maior ganho médio diário (GMD; P < 0,01) foi observado nas novilhas do tratamento de AOF. Maior taxa de lotação (P < 0,01) e ganho por área (P = 0,035) foi dectado no tratamento da BOF. No entanto, maiores quantidades de suplemento foram ofertadas por hectare (P = 0,016) no tratamento da BOF. Em relação às medidas feitas por ultrassonografia da carcaça, os animais mantidos na AOF tiveram maior área de olho de lombo (AOL; P = 0,001), maior espessura de gordura subcutânea (EGS; P = 0,001) e na picanha (EGP8; P = 0,004) em relação ao tratamento de BOF. Desse modo, as novilhas da AOF chegaram mais pesadas (P = 0,004) e com maior EGS no momento da inseminação. Assim, maior taxa de ciclicidade (P = 0,052) e proporção de novilhas púberes que ficaram gestantes (P = 0,007) foram observadas na AOF; entretanto não foi dectado diferença na taxa de prenhez geral (P = 0,223) e na taxa de perda de gestação (P = 0,221) entre os tratamentos. No Exp. 2, o PC e o peso da carcaça quente aumentaram linearmente (P < 0,001) com os TC estudados. Além disso, o consumo de matéria seca, a EGS e a AOL aumentaram ao longo do TC (efeito linear; P < 0,01). Os ganhos de AOL (P = 0,814) e EGS (P = 0,402) foram similares entre os TC, mas o ganho de gordura na P8 aumentou (efeito quadrático; P = 0,007). Os TC não afetaram o GMD (P = 0,807), ganho de carcaça (P = 0,38) e eficiência alimentar de carcaça (P = 0,840). O ganho total de carcaça (efeito linear; P < 0,01) aumentou ao longo do TC. Como conclusão do Exp. 1, os critérios de manejo do pastejo afetaram as características estruturais e nutricionais do pasto, sendo que melhor desempenho e características de carcaça foram obtidas em animais mantidos na AOF; no entanto ambos os tratamentos foram similares no desempenho reprodutivo de novilhas Nelore destinadas à reprodução aos 14 meses. Em relação ao TC no Exp. 2, conclui-se que novilhas Nelore jovens que receberam suplementação intensiva durante a recria não reduziram o desempenho e a eficiência alimentar até 105 dias de confinamento, aumentando o peso e rendimento de carcaça no abate.
The study of pasture management associated with high supplementation [10 g/kg of body weight (BW)] is a strategy to reduce the age at breeding replacement Nellore heifers. Furthermore, to take advantage of the non-pregnant heifers (empty heifers) from this system, the feedlot time (FT) study is necessary to understand the carcass deposition and evaluate the feed efficiency of these animals. In this way, two experiments were carried out. In the first experiment (Exp. 1), the effect of two forage allowance (high and low forage allowance (FA); HFA and LFA, respectively) on canopy structure, forage nutritive value, supplement intake, performance, carcass characteristics and reproductive performance during the growing phase of weaned Nellore heifers (7 ± 1 months of age) receiving high supplementation on marandu grass pasture {Brachiaria brizantha (Hochst. ex A. Rich.) RD Webster [syn. Urochloa brizantha Stapf cv. Marandu]}, under continuous stocking, submitted to the breeding season at 14 months of age. In the second experiment (Exp. 2), the effect of three FT (45, 75 and 105 days) was evaluated on performance, carcass characteristics, intake, and feed efficiency of non-pregnant Nellore heifers (16 ± 1 months of age), from Exp 1. In Exp. 1, it was observed that the management of the canopy structure in two forage allowances affected the structural and nutritional characteristics of the pasture. The HFA treatment provided greater height (P < 0.01), a greater proportion of green stem (P < 0.01), a lower proportion of green leaves (P = 0.080), lower crude protein content (CP; P < 0.01) and lower CP:in vitro dry matter digestibility ratio (IVDDM; P < 0.01) compared to LFA treatment. There was no effect of forage allowance on supplement intake (P = 0.117), but greater average daily gain (P < 0.01) was observed in animals fed HFA. Higher stocking rate (P < 0.01) and gain per area (P = 0.035) were observed in the treatment of LFA. However, greater amounts of the supplement were offered per hectare (P = 0.016) in the same system. Regarding the measurements using ultrasound, the animals kept in the HFA had greater rib eye area (REA; P = 0.001), greater back fat thickness (BFT; P = 0.001) and rump fat (RF; P = 0.004) compared to animals in LFA treatment. Thus, heifers fed HFA had heavier (P = 0.004) and greater BFT during breeding. Thus, a higher cyclicity rate (P = 0.052) and proportion of pubertal heifers that became pregnant (P = 0.043) were observed in the HFA; however, differences in overall pregnancy rate (P = 0.223) and overall pregnancy loss rate (P = 0.221) among treatments were not detected. In Exp 2, BW and hot carcass weight increased linearly (P < 0.001). In addition, dry matter intake, BFT and REA increased over FT (linear effect; P < 0.01). The REA (P = 0.814) and BFT (P = 0.402) gains were similar among FT, but the rump fat gain increased (quadratic effect; P = 0.007). Feedlot time did not affect average daily gain (P = 0.807), carcass gain (P = 0.38) and carcass feed efficiency (P = 0.840). The total carcass gain (linear effect; P < 0.01) increased with FT. In conclusion, in Exp. 1, grazing management affected the structural and nutritional characteristics of the pasture, obtained better performance and carcass characteristics of heifers in the HFA treatment; however, both treatments were similar in the reproductive performance of breeding Nellore heifers at 14 months. Regarding FT in Exp. 2, it is concluded that Nellore heifers that received high supplementation during the growing phase did not vii reduce performance and feed efficiency until 105 days of confinement, increasing weight and carcass yield at slaughter.
The study of pasture management associated with high supplementation [10 g/kg of body weight (BW)] is a strategy to reduce the age at breeding replacement Nellore heifers. Furthermore, to take advantage of the non-pregnant heifers (empty heifers) from this system, the feedlot time (FT) study is necessary to understand the carcass deposition and evaluate the feed efficiency of these animals. In this way, two experiments were carried out. In the first experiment (Exp. 1), the effect of two forage allowance (high and low forage allowance (FA); HFA and LFA, respectively) on canopy structure, forage nutritive value, supplement intake, performance, carcass characteristics and reproductive performance during the growing phase of weaned Nellore heifers (7 ± 1 months of age) receiving high supplementation on marandu grass pasture {Brachiaria brizantha (Hochst. ex A. Rich.) RD Webster [syn. Urochloa brizantha Stapf cv. Marandu]}, under continuous stocking, submitted to the breeding season at 14 months of age. In the second experiment (Exp. 2), the effect of three FT (45, 75 and 105 days) was evaluated on performance, carcass characteristics, intake, and feed efficiency of non-pregnant Nellore heifers (16 ± 1 months of age), from Exp 1. In Exp. 1, it was observed that the management of the canopy structure in two forage allowances affected the structural and nutritional characteristics of the pasture. The HFA treatment provided greater height (P < 0.01), a greater proportion of green stem (P < 0.01), a lower proportion of green leaves (P = 0.080), lower crude protein content (CP; P < 0.01) and lower CP:in vitro dry matter digestibility ratio (IVDDM; P < 0.01) compared to LFA treatment. There was no effect of forage allowance on supplement intake (P = 0.117), but greater average daily gain (P < 0.01) was observed in animals fed HFA. Higher stocking rate (P < 0.01) and gain per area (P = 0.035) were observed in the treatment of LFA. However, greater amounts of the supplement were offered per hectare (P = 0.016) in the same system. Regarding the measurements using ultrasound, the animals kept in the HFA had greater rib eye area (REA; P = 0.001), greater back fat thickness (BFT; P = 0.001) and rump fat (RF; P = 0.004) compared to animals in LFA treatment. Thus, heifers fed HFA had heavier (P = 0.004) and greater BFT during breeding. Thus, a higher cyclicity rate (P = 0.052) and proportion of pubertal heifers that became pregnant (P = 0.043) were observed in the HFA; however, differences in overall pregnancy rate (P = 0.223) and overall pregnancy loss rate (P = 0.221) among treatments were not detected. In Exp 2, BW and hot carcass weight increased linearly (P < 0.001). In addition, dry matter intake, BFT and REA increased over FT (linear effect; P < 0.01). The REA (P = 0.814) and BFT (P = 0.402) gains were similar among FT, but the rump fat gain increased (quadratic effect; P = 0.007). Feedlot time did not affect average daily gain (P = 0.807), carcass gain (P = 0.38) and carcass feed efficiency (P = 0.840). The total carcass gain (linear effect; P < 0.01) increased with FT. In conclusion, in Exp. 1, grazing management affected the structural and nutritional characteristics of the pasture, obtained better performance and carcass characteristics of heifers in the HFA treatment; however, both treatments were similar in the reproductive performance of breeding Nellore heifers at 14 months. Regarding FT in Exp. 2, it is concluded that Nellore heifers that received high supplementation during the growing phase did not vii reduce performance and feed efficiency until 105 days of confinement, increasing weight and carcass yield at slaughter.
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Palavras-chave
Reprodução, Confinamento (Animais), Forragem, Feedlots