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Abstract
The growth and litter performance of 60 Large White x Berkshire sows mated to Large White boars were measured over four reproductive cycles. At first mating, animals were allocated to four dietary treatments according to mating weight and ultrasonically determined backfat cover. A high-low feeding pattern during pregnancy was compared with a low-high pattern of meal intake, and grazing treatments with either high or low levels of a high-protein meal supplement. From Parity 2, sows on the low-high all-meal feeding pattern were changed to grazing with barley meal and vitamin and mineral supplements.
In Parity I, gilts on the low-high all-meal feeding pattern gained rnore net weight in pregnancy, lost more weight in lactation. and weaned heavier litters, after adjustment for variation in litter size. than control gilts on the high-low pattern.
Litters from sows on the grazing treatments, fed the higher protein meal supplement, were lighter at birth and weaning than litters from sows on the high-low meal feeding. The use of a cereal meal and mineral supplement for grazing sows appeared to result in a relative decline in birth weights throughout the trial. Numbers of piglets born per litter were not influenced by any dietary treatment.
Reserves of physical and chemical fat, as estimated from ultrasonically measured backfat depths, decreased in Parities I and 2, but remained static thereafter.
A straight line fitted to means showed that apparent digestible energy (ADE) intake accounted for most of the variation in mean net sow gains in Parity 1 (r2 = 0.93). This finding is discussed in relation to optimal net gains in pregnancy and currently available feeding standards.
