The effect of space restriction during rearing on the attainment of puberty and subsequent reproductive activity of female pigs

Abstract

Indoor rearing of gilts has been reported to delay the onset of puberty and reduce the expression of regular oestrous cycles in gilts. The possibility that this may be a consequence of insufficient allocation of floor space, i.e. crowding, was investigated in the present study by rearing gilts between 26 and 90 kg at two stocking densities which were based on the pigs' physical dimensions and spatial preferences and represented adequate (uncrowded) or inadequate (crowded) conditions. A total of 35 Large White/Landrace crossbred gilts were housed in groups of six in partially slatted concrete pens with two adjustable sides. Space allocation ( A, m 2) was adjusted weekly and was based on the equation A=k W 0.66 where W represented the mean group liveweight and the value of k was either 0.048 (uncrowded) or 0.025 (crowded). Daily exposure to a mature boar for 20 min day −1 commenced when the mean weight of the gilts reached 90 kg (160.9 days of age) and continued until puberty was reached or until the gilts were 250 days of age. Gilts were transferred to individual stalls in a dry sow house 10–12 days after puberty and mated at their second oestrus following daily heat checks. All mated gilts were slaughtered between 28 and 32 days after mating to determine pregnancy rate and embryonic survival. Although crowding during the 91 day rearing phase significantly reduced growth rate (uncrowded 732.0±14.1, crowded 688.0±14.1; P<0.05), there was no significant effect of treatment on either the proportion of gilts reaching puberty by 250 days of age or the mean age of the gilts at puberty (uncrowded 16 18 , 177.4 days; crowded 15 17 , 179.8 days). Among the gilts which reached puberty, although both the mating and pregnancy rates tended to be lower for the crowded gilts than for the uncrowded animals ( 13 15 vs. 16 16 mated; 9 13 vs. 14 16 pregnant at 28–32 days), and slightly fewer crowded gilts exhibited normal first oestrous cycle lengths ( 7 15 vs. 11 16 ), none of these differences were statistically significant. Neither ovulation rate nor embryonic survival were affected by treatment. These results demonstrate that space restriction which was sufficient to significantly impair growth rates during rearing did not adversely affect puberty attainment in gilts exposed to boars from 160 days of age, nor did it significantly affect subsequent reproductive performance in the limited number of animals used.