Utilization of casein or isolated soybean protein supplemented with amino acids and glucose or lactose by neonatal piglets reared artificially.

Forty-five neonatal pigs were used to compare the utilization of casein plus L-tryptophan (Try) and L-arginine (Arg) and of isolated soybean protein (ISP) plus DL--methionine (Met), L-lysine (Lys) and Try, with either glucose or lactose used as the carbohydrate source, from 1 to 29 days of age. A reference diet containing dried skim milk and soybean meal proteins was utilized. No interaction (P greater than .05) occurred between protein and carbohydrate sources. The diets containing lactose or glucose produced similar pig perforamnce, nutrient digestibility and serum levels of glucose, protein and urea nitrogen from 1 to 29 days of age. However, pigs fed the diet containing casein had higher (P less than .05) average daily gain and higher gain to feed ratios from 1 to 15 days of age than did pigs fed the diet containing ISP, while both groups were similar in performance from 15 to 29 days of age. Ether extract, crude protein, energy, ash and dry matter digestibilities and serum levels of protein were greater (P less than .05) for pigs fed the diets containing casein than for those fed the diets containing ISP. Nitrogen free extract digestibility and serum glucose and urea nitrogen were similar for pigs fed the diets containing casein or ISP. The diets that the pigs received from 1 to 29 days of age did not influence their subsequent nursery performance from 29 to 64 days of age, when all groups were fed the same diet. These results indicate that casein plus Try and Arg was superior to isolated soybean protein plus Met, Lys and Try as a source of protein for the baby pig from 1 to 15 days of age, while both protein sources produced similar perforamnce from 15 to 29 days of age.