Role of Immunomodulators in Fertility of Livestock: A review

Fertility of livestock is economically important. An optimal uterine environment is critically important for the viability of fertile spermatozoa and development of an embryo. Factors causing infertility or subfertility includes infectious diseases, functional abnormalities, genetic structural disorders and management problems. However, even in ideal laboratory and clinical conditions, the cause of only 60–70% of infertility and subfertility can be determined; this rate decreases to under 50% in field conditions. In recent times, it has been suggested that immunological factors play an important role as one of causes of infertility. In the female body, immunological infertility can develop against the zona pellucida, spermatozoa, seminal plasma and the cauda epididiymis extract. Other than during of gamete specific structures, infertility can develop due to immunity against GnRH, hCG and eCG. Pathogenic organisms may overcome the defense and lead to endometritis and mucosal denudation. Various substances, ranging from antibiotics to hormones have been tried earlier to counteract uterine infections. But these conventional therapies besides being costly causes extra harm to animal in form of development of resistance for them in microbes, residues in animal products, diseases like cyst formation etc. Difficulty in controlling predisposing factors under field conditions has drawn more attention towards the therapeutic management of the diseases. Preliminary efforts have been made to stimulate the host uterine defense mechanism through intrauterine infusion of autologous plasma in mares or E. coli LPS in cows as an alternative therapy for intrauterine application as a uterine defense stimulator in clinical cases of repeat breeding. Levamisole, a non-specific immunostimulatnt also stimulated sub-normal phagocytosis and cell-mediated response in bovines. Tinospora cordifolia, an indigenous plant used in ayurveda is known for its immunopotentiating action, plasma has been shown to have local inflammatory effect on endometrium in mares. A large variety of unrelated compounds, most of them of bacterial origin, have been shown to have immunomodulatory activities. Several studies was carried out to assess the potential use of an immunomodulators for restoring activity of the immune system and to evaluate the effect assay over reproductive function of livestock taking into consideration the reproductive state.