Interrelationship of some hormonesbelonging to HPG and energy axes inhorses during various reproductive states

Abstract

In order to reveal interrelationships of hormones during pregnancy and estrus in animals, some reproductive and metabolic hormones including FSH, inhibin B, prolactin and insulin were measured in blood serum of Mongolian horses with respective immunoassays. Concentrations of blood serum FSH, inhibin B and prolactin in mares during their estrus, early, mid and late pregnancy periods were compared. The comparisons demonstrate concentrations of FSH and inhibin B were inversely proportional especially during estrous cycle of mares. As well, these hormones were also measured in blood serum of stallions with the purpose of assessing their reproductive activity. Concentrations of both hormones were lower in blood serum of stallions, which have harems of less conceived mares or it means higher inhibin concentration results in less reproductive activity. Prolactin was minimal during estrus and early pregnancy, while it increases during late pregnancy, but there was no correlations with above two hormones. Measurements of insulin was helpful to learn whether the animal is suffering from metabolic disorder such as insulin resistance, because last half of pregnancy of mares coincides with the period of fattening of pastured animals. However, main outcome of the present study is that all above hormones might be acting in closer relationships during various reproductive states, despite they belong to different axes of endocrine system, including hypothalamic-pituitary-gonadal (FSH and inhibin)and energy (insulin and prolactin) axes.Mongolian Journal of Agricultural Sciences Vol.15(2) 2015; 10-15