Effects of food level and straw bedding during pregnancy on sow performance and responses to an ACTH challenge

Abstract

The interactive effects of straw provision and food level during pregnancy on performance, and the adrenal response to a challenge with ACTH (as a measure of chronic physiological stress) were studied over two parities. Ninety-six gilts were allocated to a 2 × 2 factorial experiment comparing food level (L = 1.6–1.8 kg (20–23 MJ DE) day−1; H = 3.0–3.2 kg (38–40 MJ DE) day−1) and the provision of straw (S = straw, N = no straw) during pregnancy. All gilts were loose housed in groups of 6 with individual feeding stalls. Significantly more N sows failed to start the second parity than S sows. H sows gained more weight and back fat over both pregnancies than L sows. There was a tendency for LS sows to gain more weight and back fat over both pregnancies than LN sows. Litter performance was not influenced by the straw treatment. HN sows had the highest concentration of basal cortisol, but no treatment effects were found in increase of salivary cortisol concentrations in response to the ACTH challenge in second parity sows. It is concluded that provision of straw may buffer the adverse effects of a low food level on weight and back fat gain in group-housed pregnant sows, but has no effect on reproductive performance. The cortisol data suggest differences between treatments to be of an acute, rather than a chronic nature.