Fatores que influenciam a temperatura corporal de vacas da raça holandesa lactantes
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Data
2017-07-24
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Universidade Estadual Paulista (Unesp)
Resumo
O objetivo do experimento foi avaliar a temperatura vaginal em parâmetros produtivos e reprodutivos. Vacas Holandesas lactantes n = 641 (209 primíparas 36,9 ± 6,54 kg de leite / d; 432 multíparas 43,9 ± 9,77 kg de leite / d) tiveram a temperatura vaginal monitorada através de termômetros, anexados a um dispositivo intravaginal como parte de um protocolo de IATF. A temperatura vaginal foi registrada a cada 10 minutos durante três dias. A temperatura ambiente e a umidade relativa (ITU) foram mensuradas usando um termômetro externo colocado dentro do barracão. Os dados foram analisados com SAS 9.4 usando correlação de Pearson, ANOVA e regressão logística. Calculou-se o estresse térmico com base na porcentagem de tempo que a vaca ficou com uma temperatura vaginal ≥ 39,1°C (PCT). As vacas foram classificadas através de quartis (AltaPCT (3º quartil; PCT-60%) e BaixaPCT; PCT-16%) para PCT e o mediana para produção de leite, que eram diferentes para primíparas e multíparas. Houve uma baixa correlação entre ITU e produção de leite com PCT (r = 0,01), indicando maior variação na termorregulação. O BaixaPCT (22,4 e 13,9%) e o AltaPCT (12,6 e 9,7%) reduziram significativamente o P/AI no dia 30 e 52 pós-IA (P < 0,01) e sem interações com ordem, escore de condição corporal e ITU observados. A cor da pelagem e a espessura do couro não influenciaram o PCT (P > 0,1). Entretanto houve interação entre cor de pelagem, PCT e produção de leite, onde independente da PCT e produção de leite, vacas de cor branca apresentaram menor prenhez (P = 0,03). Em resumo, houve uma grande variabilidade em como as vacas respondem individualmente ao estresse térmico. A prenhez foi afetada somente em vacas com alta PCT independente da ordem, produção de leite, ECC. A seleção de animais com controle eficiente da temperatura corporal apesar da alta produção de leite deve ser abordada como uma estratégia para manter a fertilidade adequada.
The aim of the experiment was to evaluate vaginal temperature on productive and reproductive traits and potential genetic contribution to thermomtolerance. Lactating Holstein cows n = 641 (209 primíparous 36,9 ± 6,54 kg milk/d; 432 multíparous 43,9 ± 9,77 kg milk/d) had vaginal temperature monitored using thermometers, attached to an intravaginal device as part of a timed-AI protocol and recorded vaginal temperature every 10 minutes for 3 days. Ambient temperature and relative humidity (THI) were monitored using an external thermometer placed inside the barn. The data were analyzed with SAS 9.4 using Pearson correlation, ANOVA and logistic regression. Heat stress was calculated based on the percentage of time the cow spent with a vaginal temperature ≥39,1°C (PCT). Cows were classified using the 75th percentile threshold (HighPCT and LowPCT) for PCT and the median value for milk, which were different for primiparous and multiparous. There was a low correlation between THI and milk production with PCT (r=0,01) indicating a large variation in thermoregulation. Multiparous LowPCT (22,4 and 13,9%) and HighPCT (12,6 and 9,7%) significantly reduced P/AI on day 30 and 52 post-AI (P < 0,01) and no interactions with parity, body condition score and THI were observed. Coat color and skin thickness did not influenced PCT. However, there was interaction between coat color, where, independent of PCT and milk production, white cows presented lower pregnancy rate (P < 0,03). In summary, there is a large variability on how individual cows respond to heat stress. Pregnancy was just affected in cows with high PCT independent of parity, milk production, BCS. Selection of animals with efficient control of body temperature in spite of high milk production should be further approached as a strategy to maintain adequate fertility.
The aim of the experiment was to evaluate vaginal temperature on productive and reproductive traits and potential genetic contribution to thermomtolerance. Lactating Holstein cows n = 641 (209 primíparous 36,9 ± 6,54 kg milk/d; 432 multíparous 43,9 ± 9,77 kg milk/d) had vaginal temperature monitored using thermometers, attached to an intravaginal device as part of a timed-AI protocol and recorded vaginal temperature every 10 minutes for 3 days. Ambient temperature and relative humidity (THI) were monitored using an external thermometer placed inside the barn. The data were analyzed with SAS 9.4 using Pearson correlation, ANOVA and logistic regression. Heat stress was calculated based on the percentage of time the cow spent with a vaginal temperature ≥39,1°C (PCT). Cows were classified using the 75th percentile threshold (HighPCT and LowPCT) for PCT and the median value for milk, which were different for primiparous and multiparous. There was a low correlation between THI and milk production with PCT (r=0,01) indicating a large variation in thermoregulation. Multiparous LowPCT (22,4 and 13,9%) and HighPCT (12,6 and 9,7%) significantly reduced P/AI on day 30 and 52 post-AI (P < 0,01) and no interactions with parity, body condition score and THI were observed. Coat color and skin thickness did not influenced PCT. However, there was interaction between coat color, where, independent of PCT and milk production, white cows presented lower pregnancy rate (P < 0,03). In summary, there is a large variability on how individual cows respond to heat stress. Pregnancy was just affected in cows with high PCT independent of parity, milk production, BCS. Selection of animals with efficient control of body temperature in spite of high milk production should be further approached as a strategy to maintain adequate fertility.
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Palavras-chave
Estresse térmico, Produção de leite, Fertilidade, Heat stress, Milk production, Fertility