Milk production in Saanen goats treated with repeated low doses of intermediate-release insulin during early lactation / Produção de leite em cabras Saanen tratadas com repetidas doses baixas de insulina de liberação intermediária durante a lactação inicial

ABSTRACT: The effect of insulin administration on the productive responses of Saanen goats during early lactation was investigated. Ten of 20 adult females were subjected to subcutaneous administration of intermediate-acting insulin (0.14UI/kg body weight) at 2, 9, and 14 days postpartum. Milk yield was measured twice daily for 13 weeks and milk samples were collected to measure protein and fat contents. Plasma levels of progesterone, insulin, non-esterifies fatty acids, glucose and other metabolites were measured. Results showed a significantly increased effect of insulin treatment on the content of milk fat and protein; moreover, milk production in the first and second postpartum weeks were higher than control group. The peak of lactation in the insulin group was achieved one week earlier in comparison to the control group. In addition, the milk production rate showed lower persistency (milk yield 13 week/milk yield at peak) in the same group. During the first four weeks of postpartum, treated animals showed greater weight loss and higher non-esterified fatty acid concentration, whereas no effect was observed on the concentration of progesterone and other metabolites. The above results indicated that repeated administration of insulin in dairy goats during early lactation increase yield and qualitative components of milk, but has substantial consequences on animal productive rate and metabolic response.

RESUMO: O objetivo do estudo foi avaliar o efeito da administração de insulina sobre a resposta produtiva de cabras Saanen durante a lactação inicial. Dez de vinte fêmeas adultas foram sujeitas à administração subcutânea de repetidas e baixas doses de insulina de liberação intermediária aos 2, 9 e 14 dias pós-parto. A produção de leite foi mensurada duas vezes ao dia, por 13 semanas, e amostras de leite foram coletadas para mensurar teores de proteína e gordura. Os níveis plasmáticos de progesterona, insulina, ácidos graxos não-esterificados (AGNE), glicose e outros metabólitos foram mensurados. Os resultados mostraram um efeito significativamente maior nos animais tratados com insulina sobre o teor de gordura e proteína no leite. Além disso, a produção de leite na primeira e segunda semana pós-parto foi maior no grupo tratado do que no grupo controle. O pico de lactação no grupo insulina foi alcançado uma semana antes em comparação ao grupo controle. Além disso, a taxa de produção de leite nos animais tratados mostrou uma menor persistência de produção de leite durante o período analisado. Durante as primeiras quatro semanas pós-parto, os animais tratados com insulina mostraram maior perda de peso e maior concentração de AGNE, enquanto não se observou nenhum efeito sobre a concentração de progesterona ou outros metabólitos. Os resultados acima indicam que repetidas doses de insulina em cabras leiteiras durante a lactação inicial aumenta o rendimento de produção e concentração de componentes qualitativos do leite, mas apresenta consequências consideráveis sobre taxa de produção animal e resposta metabólica.

Physiological and production response of dairy goats bred in a tropical climate.

The aim of this work was to determine the adaptability of Saanen and ½Saanen × ½Anglo-Nubian (½S½AN) goats bred in tropical climates. The study included 30 goats, 15 Saanen and 15 ½S½AN. The data was collected during the rainy and dry seasons. During the whole experimental period, the environment variables were recorded, as well as rectal temperature (RT), superficial temperature (ST), respiratory rate (RR) and heart rate (HR) and milk production (MP). The adaptability coefficient (AC) was calculated for both genotypes. The averages were evaluated by ANOVA at 5% probability. There was a genotype and period of year effect, as well as the interaction genotype × period of year. Pearson's simple correlation analysis was then carried out between milk production and physiological and environment variables. There was a statistical difference (p < 0.05) between the seasons for RT, ST and RR. RT, RR and HR were lower for ½S½AN than Saanen goats, regardless of the season. MP was greater in the dry season (p < 0.05) (2.52 ± 0.50 kg/day for ½S½AN and 2.41 ± 0.38 kg/day for Saanen) than the rainy season (2.17 ± 0.27 kg/day for ½S½AN and 2.28 ± 0.53 kg/day for Saanen). The MP correlations were very significant (p < 0.05), however low and negative, where it was higher when correlated with RR in Saanen goats. Under the conditions of the present study, it is concluded that the goats were influenced by climatic factors, where the rainy period was more likely to cause thermal stress in the animals.

Impacto do estresse térmico sobre a fisiologia, reprodução e produção de caprinos / Impact of heat stress on the physiology, reproduction and production of goats

Apesar dos caprinos serem considerados animais rústicos, do ponto de vista bioclimático, a associação entre elevadas temperaturas, umidade e radiação solar pode acarretar alterações fisiológicas, hematológicas, hormonais, reprodutivas e produtivas. Portanto, informações que possam esclarecer o impacto do estresse térmico sobre a eficiência desses aspectos em caprinos, analisando o ambiente em que estão inseridos, e como se comportam frente às adversidades impostas pelo clima, darão uma grande contribuição para a caprinocultura e o fortalecimento de sua cadeia produtiva. Assim, para aumentar a produtividade nas regiões tropicais, deve ser ressaltada a criação de raças que apresentem maior potencial genético de adaptabilidade para uma condição climática adversa, sendo capazes de sobreviver, reproduzir e produzir em situações de estresse térmico.

Even though goats are considered rustic animals, regarding the bioclimatic aspect, the association of high temperature, humidity and solar radiation may cause physiological, hematological, hormonal, reproductive and productive changes. Therefore, information explaining the impact of heat stress on the efficiency of these aspects on goats by analyzing the surrounding environment and how these animals behave themselves before the adversities imposed by the climate, will give a great contribution to goat breeding and the strengthening of this productive chain. Thus, to increase the productivity in tropical regions, the breed of animals presenting a major genetic potential of adaptability to adverse climatic conditions must be emphasized breeds that may be able to survive, reproduce and produce efficiently in a situation of heat stress.