A previous study (Rooke et al, 1997) showed that in normal commercial feeding conditions there were large differences between litters in live-weight gain at weaning and in immune response to inclusion of soyabean meal. The current experiment attempted to separate these maternal influences into pre- and post-partum effects and investigated whether maternal diet fatty acid composition influenced piglet performance.

Five groups of 6 sows (Large White x Landrace) were used. At weaning, sows were grouped into threes by live-weight and backfat thickness and allocated to one of three diets which were fed throughout pregnancy and lactation. Pregnancy and lactation diets were formulated to supply 12.5 and 14.0 MJ DE, 140 and 180 g CP and 4.5 and 8.5 g lysine / kg. Pregnancy diets contained 17.5 g/kg of either maize oil (M), linseed + maize oil (60:40 ratio, L) or fish oil (Tuna Orbital Oil, Scotia Pharmaceuticals Ltd, F) and lactation diets 35 g/kg oil (17.5 g maize oil + amounts in gestation diets). Six groups of 3 sows participated in a cross-fostering study. All sows were induced to farrow on day 113 or 114 of gestation. Piglets were removed from the sow until farrowing was complete to avoid colostrum consumption. Nine piglets / sow were chosen for cross-fostering from each group of 3 sows (1/diet). Piglets were grouped into threes by weight and allocated to each of the 3 sows. The piglets were reared on the sows with no access to creep feed until weaning at 28 days of age. At weaning the piglets were kept in their lactation sow groups and fed a common diet (16.3 MJ DE, 240 g CP , 15.5 g lysine / kg) based on cooked cereals, milk products and containing 150 g / kg soya bean meal for 7 days. Piglets were weighed at birth and weekly thereafter. The data were analysed using the REML procedure of Genstat to quantify variance relating to sow effects (during pregnancy and lactation) and of pregnancy and lactation diets.