Effects of lipids from various oilseeds supplied in different forms on ruminal biohydrogenation of fatty acids in vitro and on milk production and milk fatty acid composition of dairy cows

Dietary lipid supplements in ruminant diets have a long history. The main reasons for
their use comprise an increased energy density of ruminant diets, beneficial effects on
reproductive parameters as well as changes in the fatty acid (FA) composition of products of
ruminant origin for human consumption. Besides technologically processed and rumen
protected lipid supplements, oilseeds are supplemented to dairy cow diets. The ruminal lipid
metabolism especially affects the unprotected lipids entering the rumen. The relevant processes
regarding FA digestion in the rumen involve the hydrolysis of dietary lipids, the isomerisation
of FA and finally the biohydrogenation (BH) of FA. Therefore, the FA composition in rumen
fluid and subsequently in milk fat is considerably changed by the ruminal processes. The aim
of the current doctoral thesis was to assess the effects of different oilseeds with regard to BH
and changes in the FA composition in rumen fluid and in milk fat. Linseed, soybeans, sunflower
seed and rapeseed were used in forms of full-fat crushed seed and pure oil for in vitro incubation
with rumen fluid. In the subsequent in vivo study, rapeseed in both of these forms was
supplemented to a dairy cow diet.