Performance, heat tolerance response, and blood metabolites of water-restricted Xhosa goats supplemented with vitamin C

Water restriction in small ruminants is usually accompanied by a drop in feed intake, body weight, and disturbances in the normal internal milieu. However, attempts to lessen the burden of water stress with vitamin C (VC) supplementation have been greeted with conflicting reports. Therefore, this experiment was conducted to evaluate the effect of single and/or multiple VC supplementations in water-restricted Xhosa goats by evaluating their performance, heat tolerance, and blood metabolites. In total, 42 does, 12 mo old and with an average weight of 15.92 [+ or -] 2.12 kg were evaluated for 75 d. The does were distributed according to a complete randomized design into seven groups of six comparable animals: W0, without water restriction (control); W70, water restriction of 70% of ad libitum water intake (WI); W50, water restriction of 50% ad libitum WI; [W70.sup.+], water restriction of 70% of ad libitum WI plus 3 g VC daily; [W50.sup.+], water restriction 50% of ad libitum WI plus 3 g VC daily; [W70.sup.++], water restriction of 70% of ad libitum WI plus 3 g VC and extra 5 g VC given every eighth day; and [W50.sup.++], water restriction of 50% of ad libitum WI plus 3 g VC and extra 5 g VC given every eighth day. Goats under the W50 group were the most affected (P < 0.05) and the effect was more pronounced in their body condition scores (BCs). Weight loss due to water restriction was reduced by VC supplementation in treated groups. Changes in body thermal gradient, rectal temperature, cholesterol, and bilirubin were similar (P > 0.05) across the various experimental groups. The attenuation effect of VC was significant (P < 0.05) in responses to respiratory rate, [Na.sup.+], [K.sup.+], [Mg.sup.2+], [Cl.sup.-], [Ca.sup.2+], and urea. Supplementation of VC (either single or multiple) did not significantly (P > 0.05) improve the effect of water restriction on BCs, FAMACHA, glucose, globulin, alanine aminotransferase, and high-density lipoprotein. The additive effect of multiple VC significantly influenced (P < 0.05) [Na.sup.+] and [Mg.sup.2+]. Limited WI affects growth and other physiological parameters in Xhosa goats. However, supplementation of VC may be beneficial at modulating the stressful stimuli imposed by water stress. Key words: blood metabolites, thermotolerance, vitamin C, water stress, Xhosa ear-lobe