Adaptive and Ecological Significance of the Seasonal Changes in Hematological, Biochemical and Hormonal Parameters in the Tropical Goat Capra Hircus

Summary The neuroendocrine system, through which animals integrate environmental changes and decide when to reproduce, to grow and to store energy, plays a major role in adaptation to the environment. Adaptation of any vertebrate in general and ruminants in particular are influenced by climatic changes being maximally exposed to nature. Elaborating adaptive significance of ruminants in response to season-dependent ecological stresses, we selected the best window i.e., study of variations in blood biochemistry which is totally lacking for goats. Our objective was to find the season- and gender-dependent variations of blood biochemistry at (i) metabolic (glucose, cholesterol, protein, %hemoglobin) (ii) hormonal (testosterone, estrogen, progesterone, melatonin) (iii) hematological (total leucocytes count- TLC; differential leukocyte count- DLC) and, finally, (iv) oxidative load of blood (superoxide dismutaseSOD; catalase, malondialdihyde- MDA) in the goat Capra hircus during three different seasons (summer, winter and monsoon). Compared to summer significant changes were noted at metabolic level during monsoon and winter as those seasons provide for inflammatory and cold stress. Cholesterol and glucose levels were high in females than males during all three seasons. Irrespective of sexes, serum protein was highest during winter while testosterone was high irrespective of seasons; hence, males were sexually active throughout the year. Estrogen was high only during the onset of winter (October, heat phase) making the female goats short-day breeders. Melatonin, a neurohormone, regulating reproduction and immunity, was highest in winter (short days) and low during summer and monsoon. Hematological parameters were lowest during summer (long days). Blood oxidative load was high during monsoon and winter due to season-bound infections that induce oxidative stress. High metabolic and immune parameters were noted during winter and monsoon which suggest an adaptive significance in tropical goats against ecological stress induced by low temperature of winter and pathogenic invasion occurring while grazing during monsoon.