Comparative Adaptive Mechanisms of Two Indigenous Goat Genetic Resources Under Simulated Water Scarcity

Water scarcity is a major constraint to livestock production in tropical and semi-arid environments, necessitating the identification of breeds with superior adaptive capacity. This study evaluated the effects of graded water restriction (WR) on growth performance, morphometric traits, and serum biochemical responses of indigenous South African goat breeds. Thirty-six female Nguni and Xhosa goats were assigned to three water intake levels: ad libitum (W0; control), 70% (W70), and 50% (W50) of ad libitum intake in a 2 × 3 factorial arrangement. Growth performance, body measurements, and serum biochemical parameters were assessed over 75 days. Water restriction significantly reduced growth performance in both breeds (p < 0.05), with more pronounced effects under severe restriction (W50). However, Nguni goats maintained higher final body weight and experienced smaller reductions in average daily gain than Xhosa goats. Morphometric traits were generally less affected by WR, although Nguni goats consistently exhibited greater rump width. Biochemical responses revealed higher concentrations of sodium, chloride, alkaline phosphatase, and creatinine (p < 0.05) in Nguni goats, whereas Xhosa goats showed higher concentrations of urea and globulin. The findings demonstrate distinct breed-specific adaptive mechanisms to water stress, with Nguni goats exhibiting greater physiological resilience.