HORMONAL INDUCTION OF LACTATION IN PREPUBERAL AND MULTIPAROUS CROSSBRED GOATS KEPT UNDER EXTENSIVE CONDITIONS

Lactation was successfully induced in four of five non-pregnant multip arous crossbred goats (Criollo X dairy breeds) and seven of ten prepub eral animals kept under range conditions. Goats were induced to lactat e by the administration of estradiol cipionate (0.1 mg kg(-1) body wei ght (BW) day(-1)) and progesterone (0.25 mg kg(-1) BW day(-1)) for 7 d ays, and dexamethasone (16 mg per goat day(-1)) was given on days 18, 19 and 20. The adult goats induced to lactate were milked for as long as the naturally kidding goats (139 days) but they produced significan tly less milk (mean +/- SE daily yield 377 +/- 75 mi vs. 724 +/- 98 ml ; P < 0.01). Milk of the induced adult goats had similar fat content t o that of control goats (4.82 +/- 0.29% vs. 4.75 +/- 0.13%) but higher protein (4.97 +/- 0.11 vs. 4.53 +/- 0.05) and casein percentages (P < 0.05). Daily milk yield (mean +/- SE) of prepuberal goats was 190 +/- 75 mi with a peak yield of 219 +/- 82 mi at 82 days. Pregnancy rates of nulliparous goats after a 30 day mating period were not significant ly different between groups (57% and 70% for treated and control goats , respectively). The induction of lactation prepuberally did not affec t milk yield (153 +/- 19 mi and 219 +/- 118 mi for control and treated goats, respectively) nor percentage of milk constituents during the s econd naturally occurring lactation, but BW and thoracic circumference of goats subjected to an early lactation was adversely affected (P < 0.05) during the second naturally occurring lactation. It was conclude d that hormonal induction of lactation may become a feasible commercia l practice in goat herds under range conditions.