The influence of dietary energy intake during successive lactations on sow prolificacy
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From selection prior to the production of their first lifters, 101 Yorkshire x Landrace sows were allocated to be ad libitum fed either a control (CE) or high energy diet (HE) during each of four successive lactations. Diets CE and HE supplied 13.7 and 15.6 MJ. DE kg-I, respectively. Sows were treated similarly during each gestation. Although HE sows tended to have a greater digestible energy intake, they lost more weight during each lactation (P<0.05). Maternal weight gains between each farrowing decreased with successive parities (P<0.05). Litter size at the second and subsequent farrowings was greater (P<0.05) for the HE than CE sows. The overall mean litter size for the HE and CE sows was 10.1 and 9.3 piglets, respectively. A similar trend was noted for live births (9.7 vs. 8.9) and numbers weaned (8.3 vs. 7.9). There was no consistent effect of treatment on pig weights at birth or 2l d of lactation. No treatment or parity effects were evident for preweaning pig mortality. The weaning to conception interval was longer for HE sows in the first parity (14.9 vs. 1l.l d), but more CE sows were culled for reproductive problems. No treatment effects were noted for mean interval to conception, proportion mated within 8 d or subsequent farrowing rate in parities 2, 3 or 4. There was no effect of initial gilt breeding weight on the ability to produce up to four litters. It is concluded that low lactation digestible energy intake may limit subsequent litter size.