FLUID BALANCE AND MILK SECRETION IN THE FED AND FEED-DEPRIVED BLACK MOROCCAN GOAT

Small, black goats are found in arid and semi-arid regions of Morocco, but physiological adaptations that enable them to thrive in their har sh habitat have not been defined. Six goats (32+/-1 kg) were studied d uring lactation and nonlactation. Goats were kept indoors (ambient tem perature 17-24 degrees C) and studied when fed twice daily, during 48 h of feed deprivation, and after refeeding. The goats were given 800 g concentrates. They ate 740+/-20 g (lactation) and 530+/-30 g/d (nonla ctation; P<0.01), indicating that nonlactating goats voluntarily decre ased their intake of concentrates. Wheat straw was available ad libitu m and lactating goats consumed 230+/-60 g/d, while goats ate 340+/-50 g/d during nonlactation (P<0.05). Feed deprivation caused a 5% weight loss in both groups. Fed lao tating goats drank 1.5+/-0.2 l/d and nonl actating goats drank 1.0+/-0.1 l/d (P<0.05). Thus, the water/DM intake ratio was 1.7 in lactating and 1.3 in nonlactating goats. Water intak e was unchanged during the first 24 h of feed deprivation, but then it dropped. Urine volume was not significantly reduced during feed depri vation. Plasma Na concentration decreased, while total plasma protein and haematocrit increased during deprivation, indicating that hyponatr aemic hypovolaemia had developed. Plasma aldosterone increased during feed deprivation. Basal plasma glucose was elevated in lactating goats , but decreased during feed deprivation. Basal plasma insulin values w ere similar in both groups, and dropped during feed deprivation. Plasm a urea was the same in both groups before feed deprivation and increas ed similarly during deprivation. Milk volume was 700+/-48 ml/d. It dec reased by 30% the first and 57% the second day of feed deprivation. Tw o days after refeeding, milk volume was 384+/-81 ml/d. Total milk lact ose secretion decreased during feed deprivation in proportion to decli ne in milk yield. Mean milk fat was 4.2 and 6.2% (at 08:00 and 16:00 h milking, respectively). It increased to 8 and 12%, respectively, duri ng the second day of feed deprivation, and therefore milk fat secretio n decreased only 18%. Milk solids content increased in proportion to f at. Milk Na was unchanged during feed deprivation, while milk K decrea sed. In conclusion, black Moroccan goats had a low water turnover and produced milk with high solids content. In response to acute feed depr ivation, they developed hyponatraemic hypovolaemia with a drop in milk secretion like other goat breeds. However, Moroccan goats maintained water intake unchanged during the first stage of feed deprivation.