Influência da alteração do escore de condição corporal e de hormônios metabólicos pós-parto na eficiência reprodutiva de vacas nelore inseminadas em tempo fixo
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Data
2017-11-10
Autores
Carvalho, Rafael Silveira
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Universidade Estadual Paulista (Unesp)
Resumo
Para entender melhor a influência da nutrição na eficiência reprodutiva de vacas Nelore lactantes, utilizou-se o seguinte experimento: 593 primíparas, 423 secundíparas e 893 multíparas Nelore lactantes foram sincronizadas com 38,3 ± 0,4 DPP, utilizando protocolo de IATF à base de P4/E2, e inseminadas 49,2 ± 0,3 DPP. Trinta dias após IATF foi realizado DG para ressincronização das vacas não gestantes, e 30 dias após termino da EM um segundo DG foi realizado. O ECC das vacas foi avaliado no parto, na IA e no DG. O peso corporal das matrizes foi mensurado na IA e no DG, e o peso corporal dos bezerros no desmame. Foram colhidas amostras de sangue de 535 vacas (sendo, 38% de primíparas, 24% de secundíparas e 38% de multíparas) após o parto (21 ± 0,4 DPP), na IA e no DG para dosagem das concentrações séricas de IGF-I e BHB, por ELISA. Os dados do experimento foram analisados através do programa SAS® 9.4 (SAS Inst., Cary, NC). O efeito de DPP sobre o ECC se comportou de maneira diferente de acordo com a paridade, em que as secundíparas e as multíparas começaram a se recuperar entre 20 e 60 DPP e as primíparas seguiram perdendo ECC até 80 DPP (P < 0,0001). Um maior ECC ao parto melhorou os resultados reprodutivos durante a EM, em diferentes intensidades de acordo com ECC e com a paridade (P < 0,05). Não foi identificado o efeito da alteração de ECC entre o parto e a IA nos resultados da primeira IATF (P > 0,26). Maior ECC na inseminação melhorou a taxa de prenhez à primeira IATF, independente da paridade (P < 0,08). Houve efeito positivo do aumento do ECC pós-IATF na taxa de prenhez à primeira IATF (P < 0,07), exceto em multíparas com ECC ≥ 2,75 na IA, onde houve efeito quadrático com baixa variação dos resultados (P < 0,02). As concentrações séricas de IGF-1 influenciaram de forma quadrática em primíparas no pós-parto e IA, em secundíparas no DG e em multíparas na IA a taxa de prenhez à primeira IATF (P < 0,05). As concentrações séricas de BHB demonstraram ter baixa influência na probabilidade de prenhez à primeira IATF. A alteração negativa do ECC das vacas nos primeiros 80 DPP, independente do ECC no parto ou paridade, aumentou o peso dos bezerros no desmame (P < 0,05). Adequado ECC ao parto, por si só, não foi capaz de garantir altos índices produtivos em todas as situações, no entanto demonstrou ser fundamental para garantir boa eficiência dentro do sistema de cria, devido à dificuldade em se ganhar ECC no pós-parto.
This experiment was developed to better understand how nutrition can influence the reproductive efficiency of suckled Nelore cows. Cows, 593 primiparous, 423 second parity and 893 multiparous were assigned at 38.3 ± 0.4 days postpartum to an estrus synchronization + fixed time artificial insemination (FTAI) protocol, then inseminated at 49.2 ± 0.3 days postpartum. Thirty days after FTAI, an initial pregnancy diagnosis (PD) was performed via transrectal ultrasound to identify non-pregnant cows for resynchronization, which was followed by a second PD 30 days after the end of the breeding season. The body condition score (BCS) of cows was evaluated at calving, at artificial insemination (AI) and at initial PD. Body weight of the cows was measured at AI and at PD, and the body weight of calves taken at weaning. Blood samples were collected from 535 cows (38% of primiparous cows, 24% of second parity cows and 38% of multiparouscows) after calving (21 ± 0.4 days postpartum) at AI, and at initial PD. Concentrations of IGF-I and BHB were measured by ELISA assay. Data were analyzed using SAS® 9.4 (SAS Inst., Cary, NC). There was an effect of days postpartum on BCS by parity, where the nadir of curve occurred between 20 and 60 days postpartum in second parity cows and multiparous cows, but the primiparous cows continued to lose BCS up to 80 days (P < 0.0001). Greater BCS at calving positively impacted the reproductive results during the breeding season at different levels based on score and parity (P < 0.05). Positive changes in BCS between calving and AI did not improve pregnancy rate of the first FTAI (P > 0.26), however, increased BCS at AI improved pregnancy rate at the first FTAI (P < 0.08), except in multiparous cows with BCS ≥ 2,75, where there was a quadratic effect with low variation of results (P < 0.02). There was a positive correlation between BCS between AI and PD and pregnancy rate at the first FTAI, regardless of parity (P < 0.07). Serum concentration of IGF-1 influenced the pregnancy rate at first FTAI quadratically in primiparous cows at postpartum and AI, in second parity cows at PD and in multiparous cows at AI (P < 0.05). Serum BHB concentration had a lowly influenced on the probability of pregnancy at the first FTAI. 27 Negative BCS change in cows in the first 80 days postpartum, regardless of BCS at calving or parity, increased calf weight at weaning (P < 0.05). Adequate BCS at calving is the best predictor of improved reproductive results vital to ensuring efficiency within a cow-calf operation as it is more difficult to gain BCS during the early postpartum period, however it cannot guarantee high reproductive success in all situations.
This experiment was developed to better understand how nutrition can influence the reproductive efficiency of suckled Nelore cows. Cows, 593 primiparous, 423 second parity and 893 multiparous were assigned at 38.3 ± 0.4 days postpartum to an estrus synchronization + fixed time artificial insemination (FTAI) protocol, then inseminated at 49.2 ± 0.3 days postpartum. Thirty days after FTAI, an initial pregnancy diagnosis (PD) was performed via transrectal ultrasound to identify non-pregnant cows for resynchronization, which was followed by a second PD 30 days after the end of the breeding season. The body condition score (BCS) of cows was evaluated at calving, at artificial insemination (AI) and at initial PD. Body weight of the cows was measured at AI and at PD, and the body weight of calves taken at weaning. Blood samples were collected from 535 cows (38% of primiparous cows, 24% of second parity cows and 38% of multiparouscows) after calving (21 ± 0.4 days postpartum) at AI, and at initial PD. Concentrations of IGF-I and BHB were measured by ELISA assay. Data were analyzed using SAS® 9.4 (SAS Inst., Cary, NC). There was an effect of days postpartum on BCS by parity, where the nadir of curve occurred between 20 and 60 days postpartum in second parity cows and multiparous cows, but the primiparous cows continued to lose BCS up to 80 days (P < 0.0001). Greater BCS at calving positively impacted the reproductive results during the breeding season at different levels based on score and parity (P < 0.05). Positive changes in BCS between calving and AI did not improve pregnancy rate of the first FTAI (P > 0.26), however, increased BCS at AI improved pregnancy rate at the first FTAI (P < 0.08), except in multiparous cows with BCS ≥ 2,75, where there was a quadratic effect with low variation of results (P < 0.02). There was a positive correlation between BCS between AI and PD and pregnancy rate at the first FTAI, regardless of parity (P < 0.07). Serum concentration of IGF-1 influenced the pregnancy rate at first FTAI quadratically in primiparous cows at postpartum and AI, in second parity cows at PD and in multiparous cows at AI (P < 0.05). Serum BHB concentration had a lowly influenced on the probability of pregnancy at the first FTAI. 27 Negative BCS change in cows in the first 80 days postpartum, regardless of BCS at calving or parity, increased calf weight at weaning (P < 0.05). Adequate BCS at calving is the best predictor of improved reproductive results vital to ensuring efficiency within a cow-calf operation as it is more difficult to gain BCS during the early postpartum period, however it cannot guarantee high reproductive success in all situations.
Descrição
Palavras-chave
ECC, IGF-I, BHB, nutrição pós-parto, vaca Nelore parida