DEGRADATION OF CRUDE PROTEIN AND QUALITY OF UNDEGRADABLE PROTEIN IN UNTREATED OR FORMALDEHYDE-TREATED RAPESEED MEAL

Rapeseed (B. campestris) meal was treated with a sugar-alcohol-formaldehyde complex (Protona) using 0, 0.4 and 0.8 g formaldehyde (HCHO) 100 g crude protein. Degradation of crude protein was measured in rumen-fistulated sheep by the nylon bag technique. The experimental diet was composed of hay, grass silage and barley mean in proportions of 1 : 1 :1 on a dry matter basis, and the sheep received a total of 2.0 kg dry matter/100 kg live weight per day. The amino acid composition of the original and undegradable proteins was also studied. Degradation of crude protein was severely reduced by HCHO treatement. Degradability after incubation for 2, 5 or 9 h for the untreated meal was 35.4, 39.7 and 64.2%; for meal treated with 0.4 g HCHO/100 g it was 2.1, 17.6 and 30.5%, and for meal treated with 0.8 g HCHO/100 g it was 3.6, 5.3 and 9.0%, respectively. Among the amino acids, methionine tended to be the most easily degradable in the rumen. Generally, the effect of rumen fermentation on the amino acid composition between the original and undegraded protein was small, and it was further decreased when the rapeseed meal was treated with formaldehyde.