The partition of body-weight gain in the pregnant sow

Abstract

1. 1. The body-weight gain of pregnant gilts was partitioned into reproductive (gravid uterus and mammary tissue) and net maternal components and was compared at feeding levels of 1.8 and 2.5 kg/day (20 and 30 MJ metabolizable energy (ME), respectively), at three specific stages of gestation; 40–60 days (early), 60–80 days (mid) and 90–110 days (late). Non-pregnant litter sisters were provided for comparison. 2. 2. The increase in body weight of the animals was directly related to the level of feed intake and was significantly higher for the pregnant animals. 3. 3. Reproductive gain increased during pregnancy and was only dependent upon feeding level in late gestation. The net maternal gain and the differences between pregnant and non-pregnant animals varied with both feeding level and stage of gestation. Calculation of the rates of gain revealed that it was only in late gestation that the net maternal gain of the pregnant animals at the high feed intake was lower than that of the non-pregnant animals. At the low feed intake, on the other hand, there was a progressive decrease in the maternal tissue deposition of the pregnant animals with stage of gestation, and with the exception of the values in early pregnancy, they were always lower than those of their non-pregnant sisters. 4. 4. The implications of the changes in maternal body weight on the long-term reproductive performance and metabolic status of the sow are discussed.