Fábio Luís Henrique

Heat stress and ACTH administration on cortisol and insulin-like growth factor I (IGF-I) levels in lactating Holstein cows

ABSTRACT Physiological and productive responses were studied in five Holstein cows in thermal comfort (T1), stress by exogenous adrenocorticotropic hormone (ACTH) administration (T2) and heat stress (T3) to compare acute and punctual stress (ACTH) and prolonged stress (heat stress). During T1 and T2, cows were housed in a climatic-free stall barn. In T3, the animals were kept in a climatic room (air temperature of 37°C from 08:00 to 13:00 h, and of 26°C from 14:00 to 07:00 h) for 7 days. Milk yield, rectal temperature (RT), respiratory rate (RR) and blood samples were obtained before, during and after all treatments. In T1 at 08:00 h, RT and RR were below the upper critical limit. Simultaneously, cortisol and insulin growth-factor I (IGF-I) were within the normal limits. After ACTH administration (T2), cortisol significantly increased, reaching maximum levels at 60 min and returning to basal levels at 300 min. However, IGF-I was not affected. During T3, Holstein cows did not effectively dissipate their body temperature and RT, RR and cortisol significantly increased. There was a 26.6% reduction in milk production after heat stress (P < .05). Prolonged heat stress was more stressful and cows had higher levels of CORT in T3 than in T2 even before the increase in body temperature. Although the total amount of cortisol and IGF-I presented a negative and significant Pearson correlation (r = −0.79), IGF-I was not significantly influenced by heat stress or ACTH administration, and the relationship between IGF-I and heat stress remains controversial.

Bem-estar durante o período gestacional de ovelhas: uma breve revisão

Nesta revisao, objetiva-se abordar praticas e cuidados relacionados ao bem-estar de ovelhas durante a gestacao em suas fases distintas. O bem-estar tem sido foco de estudos em diversas areas na ovinocultura, mas pouco se tem discutido a respeito de boas praticas durante o periodo gestacional. A gestacao e um ponto-chave para produtividade e rentabilidade da ovinocultura, e os bons cuidados neste periodo podem evitar problemas futuros. Dessa forma, sao abordados aspectos principais do comportamento ovino, pontos relacionados a reproducao, gestacao e relacao materno-filial. Tambem sao discutidos os impactos do estresse pre-natal nas funcoes fisiologicas, neuroendocrinas, reprodutivas e de desempenho dos cordeiros. Estas consideracoes permitirao o melhor entendimento do bem-estar positivo das ovelhas gestantes por meio de aspectos nutricionais, ambientais e de manejo que favorecem a gestacao, o parto e o nascimento de cordeiros saudaveis.