DescriptionDuring the lactation period, the foundation is laid for post-weaning reproductive performance, i.e. the weaning-to-oestrus interval, farrowing rate and litter size, and -shown more recently- the quality of the subsequent litter, in terms of birth weight and birth weight variation. These parameters are influenced by differences in suckling intensity and energy balance during lactation, which create differences in the release of pituitary gonadotrophic hormones LH and FSH and the metabolic hormones and metabolites (e.g. IGF-1) which consequently affect follicle development during and after lactation.Young sows are particularly susceptible to a reduced reproductive performance after lactation as they have a low feed intake capacity and a high demand for milk production. As a result, sows will mobilise substantial body reserves, which impacts subsequent reproductive performance.Over time, sow genetics has changed and specifically the continuous selection for larger litter size and for more lean sows with lower fat mass may further impair postweaning fertility of young sows. In this presentation, results from a recent PhD study at Wageningen University (Costermans, 2020) will be highlighted. In one of her studies, first parity TopigsNorsvin sows were either fullfed (6.5 kg) or feed restricted (3.25 kg) during the last 2 weeks of a 24 day lactation period. Feed restriction resulted in a higher body weight loss and in loin muscle loss, but in a similar backfat loss during lactation and the sows also had lower plasma insulin-like growth factor (IGF1) levels and higher plasma creatinine levels in the last week of lactation. The sows were sacrificed at 2 days after weaning to retrieve the ovaries. In the restricted sows, the follicles in the presumptive ovulatory pool were smaller, with lower steroid levels, and the oocytes from these follicles were less competent, as shown by a lower degree of cumulus expansion of the cumulus-oocyte-complexes (COC) during in vitro maturation, a lower fertilisation rate after subsequent in vitro fertilisation, and higher rates of polyspermy (Costermans et al., 2019, DOI: 10.1093/biolre/ioz175).Several metabolic and follicular changes were related. For example, in the fullfed sows, a higher backfat loss and loin muscle loss were related with a smaller follicle size. In both groups, plasma IGF1 levels at 2 days after weaning were positively related with follicular fluid IGF1 levels and were both positively related with the cumulus expansion during in vitro maturation. These findings show that body condition losses during lactation impairs follicular development and oocyte competence just after weaning which likely impacts post-weaning fertility in these modern lean sows. It remains therefore important to search for ways to increase body condition at farrowing, increase feed intake during lactation or improve the dietary composition (i.e. IGF1 stimulation) during lactation.
|Period||18 Sep 2021|
|Event title||Reproduction workshop van de Leman Swine conference|