| Abstract | Thirty-six yearling Boer goat (BOE), Katahdin sheep (KAT), and Spanish goat wethers (SPA) were used to study appropriate conditions to evaluate resilience to restricted drinking water availability. Moderate quality grass hay was consumed ad libitum with concentrate (80% corn, 20% soybean meal) supplemented at 0.5% BW. Baseline conditions were determined in the last 2 wk of a 3-wk period (i.e., 100% level). Thereafter, water availability was decreased by 10% every 1 (1X) or 2 wk (2X) to 40% of baseline intake (i.e., 90, 80, 70, 60, 50, and 40% levels), but also with 2 wk at 40% for the 1X restriction treatment. There was an interaction (P < 0.001) between animal type and restriction level in hay DMI, with values of 346, 360, 358, 276, 286, 235, and 176 g/d for BOE, 656, 592, 592, 469, 522, 407, and 307 g/d for KAT, and 392, 390, 368, 273, 298, 298, and 219 g/d for SPA at levels of 100, 90, 80, 70, 60, 50, and 40%, respectively (SE = 29.1). Moreover, hay DMI by 2X wethers was much lower in wk 2 vs. 1 at the 40% level (week × level interaction, P = 0.008; 409, 369, 345, 377, 336, and 276 g/d in wk 1 and 428, 398, 312, 352, 310, and 203 g/d in wk 2 at 90, 80, 70, 60, 50, and 40% levels, respectively; SE = 23.4). Restriction level affected (P < 0.001) plasma cortisol concentration in 2X wethers on the last day at each level (12.4, 14.0, 23.3, 26.4, and 32.6 nmol/l for 100, 70, 60, 50, and 40% levels, respectively; SE = 3.62). Plasma vasopressin concentration in 2X wethers at the end of each week at 60, 50, and 40% levels was affected by an interaction (P = 0.006) between week and restriction level (3.98, 5.61, and 7.84 in wk 1 and 6.40, 7.22, and 7.06 pmol/l in wk 2, respectively; SE = 0.564). In conclusion, there was some indication that DMI by KAT was more subject to adverse effects of very low water availability but not mild restriction compared with goats. Based on vasopressin concentration, a length of at least 2 wk rather than 1 with a set level(s) of restricted water availability seems desirable, which might also increase meaningfulness of measures such as BW. Results for DMI and cortisol concentration suggest appropriateness of a maximum restriction level of 50%. |
