RAPESEED PROTEIN SOURCES AND AMINO ACID SUPPLEMENTATION OF DIETS FOR WEANLING RATS

Abstract

The nutritive values of heated or unheated rapeseed flours (RF), and heated rapeseed protein concentrate (RPC) were determined with weanling rats. Dehulled Bronowski rapeseed (Brassica napus) was solvent-extracted and ground to prepare the RF. It was heated, water- and solvent-extracted and ground to prepare the RPC. Rats were fed ad libitum for 26 days on diets containing 1.6% total nitrogen (dry matter basis) in three different experiments. A diet containing casein was used as a standard for experiment 1. Weight gains (g/day), dry matter intakes (g/day) and weight gain/protein intake for rats in experiment 1 fed the various diets were: casein, 2.71, 9.4, 2.82; unheated RF, 3.30, 10.8, 3.48; and RPC, 4.03, 11.6, 3.89. A diet containing heated RF increased (P < 0.01) rat weight gains (3.95 vs. 3.19 g/day), feed intakes and weight gain/protein intake compared with the unheated RF diet. The addition of one or more limiting amino acids, based on chemical analysis (lysine, methionine, isoleucine) to the RPC diet caused no significant increase in rat weight gains or weight gain/protein intake. Lysine added to the unheated RF diet (total lysine 7.9 g/16 g nitrogen) reduced weight gains and feed intakes by rats (P < 0.05). Liver hypertrophy in rats fed the unheated RF diet was reduced by heating the RF (6.9 vs. 6.3 g/100 g body weight). Livers from rats fed the casein and RPC diets were 5.2 and 5.9 g/100 g body weight. These results show that RPC has a high nutritive value for rat growth, and that heating and water extraction increase the feeding value of RF.