Alimentary infertility in female cattle: Part ІІ – the effect of macronutrients on reproductive function (Overview)

Macronutrients are direct participants in the most important biochemical processes, and their deficiency or excess leads to metabolic disorders, which, in turn, is a direct cause of infertility. Thus, an excess of energy leads to diseases of the uterus and ovaries, violations and inferiority of sexual cycles, reduced fertility, abortions, difficult births, and litter retention. Energy deficit causes a delay in the onset of puberty, formation of persistent corpora lutea and cysts of follicles, violation of the rhythm of the sexual cycle and the process of ovulation, low fertility, embryonic mortality, abortions, and postpartum pathologies. An excess of protein causes changes in the hormonal balance and sexual cycle, deterioration of oocyte maturation and embryo development, disruption of intrauterine development and the occurrence of abortions, increased frequency of gynecological diseases, disruption of the course of childbirth and the postpartum period, and the birth of offspring with reduced resistance. Instead, protein deficiency leads to alimentary infantilism in heifers, delay in their sexual and physiological maturity, reduction in the mass of the ovaries, pituitary gland, adrenal glands, and thyroid gland, disruption of the rhythm of sexual cycles, a weak manifestation of estrus and desire, low fertility, resorption of embryos, reduced survival of embryos and abortions, premature births, prolongation of the process of uterine involution, decrease in weight, viability and immunity of neonatal calves. Violation of carbohydrate metabolism is associated with changes in the amount and nature of estrous mucus, inferiority of the sexual cycle, reduced fertility, disruption of intrauterine and neonatal development, metabolism, contractile function of the uterus, and restoration of ovarian activity after calving. Due to a violation of fat metabolism, there is a decrease in the level of reproductive hormones (progesterone, prostaglandins), the growth of follicles and eggs, fertilization, an increase in the number of abortions, and embryonic mortality. Therefore, control of the intake of the necessary macronutrient contents – proteins, carbohydrates, and fats - contributes to proper metabolism and, accordingly, the correct functioning of the reproductive function, and therefore a preventive measure of alimentary infertility.