Jouko Setälä

Degradation of crude protein and quality of undegradable protein in untreated or formaldehyde-treated rapeseed meal

Abstract Rapeseed ( Brassica 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 rumendashfistulated sheep by the nylon bag technique. The experimental diet was composed of hay, grass silage and barley meal 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 liveweight per day. The amino acid composition of the original and undegradable proteins was also studied. Degradation of crude protein was severely reduced by the HCHO treatment. 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.

Ruminal degradation and in vivo digestibility of processed rapeseed meal

The digestibility and nutritive value of rapeseed meal processed in different ways were studied with adult rams fed on alkali-treated straw. The rumen degradability was determined by the nylon bag technique. The rapeseed meal feeds were: 1) untreated rapeseed meal, 2) heat-treated rapeseed meal (2—5 sec. at over 100°C), 3) heattreated rapeseed meal + 5 % urea phosphate and 4) heat-treated rapeseed meal + 10 % rapeseed hulls. The heat treatment reduced the rumen degradation and in vivo digestibility of the rapeseed meal, althoughnot significantly (P > 0.05). Addition of urea phosphate to the heattreated rapeseed meal increased the ruminal degradability of the crude protein and improved the digestibility of all the constituents of the rapeseed meal, especially that of crude fibre (P > 0.05). The rapeseed hulls had no noticeable effect on digestibility.