NUTRIENT DIGESTIBILITIES AND COMPARISON OF MEASURES OF FEED ENERGY FOR GILTS FED RATIONS VARYING IN ENERGY AND PROTEIN LEVEL DURING GROWTH, GESTATION AND LACTATION

Abstract

An experiment with 20 gilts, fed at different levels of energy and protein intake, was conducted to investigate the apparent digestibility of nutrients during growth, gestation and lactation; and to compare apparent digestible energy (DE) and total digestible nutrients (TDN) as measures of the energy value of swine rations.Apparent protein digestibility averaged 76 per cent and did not vary between periods (growth, gestation, lactation), but apparent digestibility of other nutrients did vary. Digestibility of crude fat in the feeds ranged from 46 to 76 per cent, while 15 per cent added stabilized tallow had a digestibility of over 94 per cent. The digestibilities of dry matter, protein and crude fiber were improved and digestibility of nitrogen-free extract reduced when gilts received supplemental fat in their ration. Increasing the level of protein in the ration tended to increase protein digestibility. There was a significant littermate effect on digestibility of protein, fat and TDN.The determined DE and TDN values were similar to calculated values and did not differ significantly between periods. The correlation coefficient (r) between kcal. DE/gm. of feed and percentage TDN was.93. The r between coefficients of digestibility for energy and for dry matter was.95 and between coefficients of digestibility for energy and for organic matter was. 96. An average ratio of 2,028 kcal. DE/lb. TDN or 4.47 kcal. DE/gm. TDN was found. There were differences in this ratio between rations and between periods.