Reconstitution of body reserves in multiparous sows during pregnancy: effect of energy intake during pregnancy and mobilization during the previous lactation.

Multiparous Large White sows were used in two experiments to determine the effects of energy intake on the reconstitution of body reserves during pregnancy. In Exp. 1, 21 sows received one of three different energy levels during pregnancy: 7.4, 8.8, or 10.4 Mcal DE/d. In Exp. 2, two energy levels (7.9 and 9.2 Mcal DE/d) were fed to 36 sows that mobilized low or high amounts of body reserves during the previous lactation (6 or 12 pigs per litter, respectively). Nitrogen balances were conducted during five 7-d periods at 11, 32, 53, 82, and 104 d of gestation. All the experimental sows were slaughtered and dissected at the end of pregnancy; 24 control sows were similarly slaughtered at mating in order to estimate composition of BW gain, according to the comparative slaughter technique. In the two experiments, average nitrogen (N) retention increased linearly with energy supply from 9.9 to 14.5 g/d in Exp. 1 (P < .001) and from 10.2 to 12.5 g/d in Exp. 2 (P < .05). Nitrogen retention was not affected by the extent of mobilization of body reserves during the previous lactation in Exp. 2. In both experiments, carcass weight (P < .001), muscle weight (P < .01), and dissectable fat weight (P < .001, Exp. 1; P < .01, Exp. 2) increased with energy supply. We conclude that in high-producing modern multiparous sows, energy supply during gestation is a limiting factor for N retention and muscle weight gain and should be approximately 8,500 kcal DE/d to ensure adequate restoration of body reserves.