The effects of type and level of feeding of sows during pregnancy

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Abstract
The growth performance of 48 Large White × Berkshire sows mated to half-sib Berkshire boars was measured over three reproductive cycles. At first mating, animals were allocated to four dietary treatments according to mating weight and ultrasonically determined backfat cover. The four treatments were factorial involving two levels of feed intake of either an all-meal ration or a combination of meal and pasture herbage. The high level of feeding (average 2.2 kg meal daily) resulted in satisfactory net sow gains in pregnancy and only moderate estimated losses of between 6.2 and 10.4 kg of subcutaneous plus flare fat during the trial. The lower level of feeding (average 1.7 kg meal daily) resulted in low net sow gains in pregnancy and large losses of 16.2 kg of fat over the trial. Increasing the level of feeding at the beginning of pregnancy might have resulted in more satisfactory sow peformance at the lower feeding level. Pasture herbage was found to be a useful feed for sows, but its daily meal equivalent value was not as high as that of 1.36 kg of meal. An indicated positive linear relationship between net sow gain and the change in the amount of carcass fat during pregnancy suggests that there would be little change in carcass fat if net sow gains in pregnancy were about 20 kg.