Protein, fat and carbohydrates in the diets of pigs between 7 and 28 days of age

Abstract

ABSTRACTIn two experiments, pigs were weaned at 4 to 5 days of age and offered dry diets based on milk proteins and tallow. Live-weight gains between 7 and 28 days of age were 220 g/day with feed conversion ratios of 0·80 when the optimum diets were given.Expt 1 was a 2 × 2 × 2 factorial with eight pigs per treatment. There were two sources of carbohydrate, lactose and wheat starch, two levels of fat, 40 and 250 g/kg and two levels of crude protein, 140 and 250 g/kg of the diet. There was no significant difference in the performance of pigs when they were fed lactose or wheat starch as the source of carbohydrate. However, the feed intake of the pigs and their weight gains and apparent digestibilities of dry matter and nitrogen were lower when the diets contained 250 g fat/kg than when the diets contained 40 g fat/kg.In Expt 2 six diets were fed to 12 pigs each. The diets contained 150, 180, 210, 240, 270 or 300 g/kg of crude protein. Weight gains and nitrogen retention showed a positive correlation (r= 0·997) with the dietary nitrogen intake but there was no statistical increase in these parameters above the 270 g crude protein/kg level. The apparent digestibilities of dry matter and nitrogen showed a similar trend. A value of 141 mg nitrogen/day per kg M0·75was estimated as the metabolic endogenous loss of nitrogen.