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Efeito do stress térmico na produção e reprodução em ovelhas de leite
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Abstract(s)
Nos últimos anos têm ocorrido alterações climatéricas, acentuando-se a existência de uma época muito quente e seca e, outra, mais fria ou chuvosa, o que penaliza a agricultura incluindo a produção animal. Estas alterações originam um decréscimo da produção de alimentos tanto para o verão como para o inverno. Os ovinos são uma espécie animal tolerante à variação de temperatura com uma termoneutralidade entre os 5-28ºC. Temperaturas superiores têm uma grande influência na sua produção e reprodução, especialmente nos animais de aptidão leiteira. Durante os períodos de stress térmico, podem ser implementadas diferentes estratégias para a manutenção da homeotermia e simultaneamente da produção dos litros de leite esperados com a mesma qualidade. Assim poderá ser necessário realizar alterações do horário de alimentação, ou seja, realizar alimentação completa ao final da tarde, se necessário otimizar com complementos minerais e antioxidantes, ter locais sombrios e arejados para os animais descansarem e manterem o seu bem-estar. A nível reprodutivo, as fases mais afetadas pelo excesso de calor são a folicologénese bem como a oogénese e a espermatogénese. A alimentação pobre aliada ao excesso de calor durante a gestação induz retardamento do crescimento fetal e pouca viabilidade nos recém nascidos. A aposta na genética é essencial, pois outra estratégia é realizar cruzamentos de animais mais resistentes ao calor, diminuindo as adversidades causadas pelo stress térmico.
In the last few years, a climate change has been observed in the form of extreme weather, as a very dry and hot season and a cooler or rainy one, which penalizes agriculture including animal farming. There is a decrease in food production for both the summer and to store for the winter. Ovine are an animal species tolerant to changes in temperature, being their thermal neutrality between 5ºC to 25ºC.The temperature rise upper critical point has a great impact in their production and reproduction especially for dairy sheep. In order to be able to maintain the liters of milk expected with the same quality and to reach homeothermy, it may be necessary to change the feeding schedule, ie, carry out the feeding in the evening and if necessary to optimize with mineral and vitamin supplements. Moreover, to have dark and airy places allowing the animals to rest and maintain their well-being. Regarding reproduction, the most critical phases are folliculogenesis and oogenesis as well as spermatogenesis. High temperatures allied to poor nutrition during gestation induce fetal growth retardation and little viability of newborns. The focus on genetics is essential as another strategy that must be implemented in order to reduce the hardships caused by thermal stress crossing animals more heat-tolerant.
In the last few years, a climate change has been observed in the form of extreme weather, as a very dry and hot season and a cooler or rainy one, which penalizes agriculture including animal farming. There is a decrease in food production for both the summer and to store for the winter. Ovine are an animal species tolerant to changes in temperature, being their thermal neutrality between 5ºC to 25ºC.The temperature rise upper critical point has a great impact in their production and reproduction especially for dairy sheep. In order to be able to maintain the liters of milk expected with the same quality and to reach homeothermy, it may be necessary to change the feeding schedule, ie, carry out the feeding in the evening and if necessary to optimize with mineral and vitamin supplements. Moreover, to have dark and airy places allowing the animals to rest and maintain their well-being. Regarding reproduction, the most critical phases are folliculogenesis and oogenesis as well as spermatogenesis. High temperatures allied to poor nutrition during gestation induce fetal growth retardation and little viability of newborns. The focus on genetics is essential as another strategy that must be implemented in order to reduce the hardships caused by thermal stress crossing animals more heat-tolerant.
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Keywords
Ovelhas Stress térmico Produção de leite Reprodução Saúde do úbere Genética Dairy sheep Heat stress Milk yield Reproduction Udder health Genetics