Maintaining sow reproductive efficiency while increasing lactation length can be achieved by stimulating a behavioural oestrus and ovulation during lactation. This experiment tested the hypothesis that removing a portion of the litter (split weaning)on d 18 post-parturition coupled with boar exposure would enable ovulation and oestrus to occur prior to full weaning.Seventy-two multiparous (parity 2.9 ± 0.17; range 2-6) sows were used in this experiment, which was conducted in four replicates. On d 2 of lactation litter size was standardised to 10 piglets per sow. Sows were weighed on days 1,17 and 30 of lactation.On d 17 of lactation sows were weighed and allocated based on liveweight (LW) change to one of four treatments; 0 (SPWO), 3 (SPW3), 5 (SPW5), or 7 (SPW7) of their heaviest piglets completely removed for the remainder of lactation (n=18 sows/treatment).From d 18 of lactation until complete weaning on d 30 post-partum, sows were taken daily to a detection mating area, where they received 20 minutes of fenceline boar exposure. The interval from split weaning to expression of behavioural oestrus, the duration of oestrus, and the proportion of sows expressing oestrus was recorded. A general analysis of variance model, with replicate and parity built in, was used to study the effects of treatment on all measures recorded (Genstat, 10* Edition, Rothamsted Experimental Station, Harpenden).
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