INFLUENCE OF SOURCE AND LEVEL OF ENERGY AND LEVEL OF PROTEIN INTAKE ON SOW PERFORMANCE DURING GROWTH, GESTATION, AND LACTATION: I. GAIN, ENERGY REQUIREMENTS, AND REPRODUCTIVE PERFORMANCE

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Abstract
From an average initial weight of 44 lb to the end of the second lactation, 60 sows (littermates from 12 litters) were fed two levels and two sources of energy and two levels of protein in 5 ration groups. To 215 lb liveweight a restriction of energy, with or without protein restriction, resulted in slower gains, improved efficiency of energy (total digestible nutrients or apparent digestible energy) utilization and lower backfat thickness. Sows fed rations formulated to meet U.S. N.R.C. nutrient requirements, and allowed no access to pasture, performed similarly during two gestation and lactation cycles when they were fed ad libitum during growth and 6 lb per day during gestation or when they were restricted in feed intake by 20% during growth and 8% during gestation. During lactation all sows were fed at an energy level based on the number of suckling pigs. The addition of 20% extra protein to the ration of sows fed at a restricted level, full-feeding sows during gestation that had been restricted during growth, or the addition of 15% stabilized tallow to supply 20% of the energy in the rations during growth and reproduction had no significant effect on conception rates, number, or weight of pigs born alive or weaned. Sows fed the ration containing tallow at an intake to equalize energy consumption with sows full-fed the control ration were heavier at the end of the experiment than the other sows.Within lots, there were significant positive correlations between weight gain during the first gestation and loss during the first lactation, gain during the first and second gestation, gain during gestation and litter birth weight as well as litter weaning weight, litter birth weight and litter weaning weight, and number of pigs born alive following each gestation. Between lots, which gives an indication of nutritional effects, gain in weight during gestation was negatively correlated (r = −.73) with the number of pigs born alive.