Protection of the unsaturated fatty acids of dried grass against biohydrogenation in the rumen

Abstract

Ryegrass (Latium sp.) , treated with HCHO (formaldehyde) after drying, was incubated with rumen fluid to examine the effect of HCHO treatment on biohydrogenation of the constituent unsaturated fatty acids. Increased levels of HCHO treatment in the range 0.5 to 2.0 g/100 g dried grass gave increasing protection of 18:3 from biohydrogenation and there was a maximum of about 85% 18:3 remaining unhydrogenated after 24-h incubations. Incubations using untreated grass converted most of the 18:3 to 18:1. Despite these observed reductions in biohydrogenation, the proportions of 18:2 and 18:3 in the milk fat did not increase when HCHO-treated dried grass was used in a paired-feeding experiment with monozygous twin cows. The changes in milk yield and milk composition were consistent with a reduced intake. 297