1. Surgically prepared lactating goats were used to obtain quantitative information on the biohydrogenation and absorption of dietary fat, and on the mammary uptake and transfer into milk fat of the complex mixture of cis- and trans-isomers of octadecenoate that arise during ruminal biohydrogenation. 2. About 90% of dietary linolenate, linoleate and oleate was hydrogenated in the rumen, and the...

The biohydrogenation (BH) theory represents a unifying concept to explain the basis for diet-induced milk fat depression (MFD) where unusual intermediates of ruminal fatty acid BH accumulate in the rumen and eventually reduce milk fat synthesis in the mammary gland. Under certain dietary situations the rumen environment is altered and a portion of BH occurs via a pathway that produces trans-10,...

Advances in knowledge of ruminant nutrition and metabolism during the second half of the twentieth century have been reviewed. Part I is concerned with metabolism in the rumen: Part II discusses utilization of nutrients absorbed from the rumen and lower tract to support growth and reproduction. The time frame was prompted by the crucial advances in ruminant physiology which arose from the work ...

There is considerable interest in altering the fatty acid composition of milk with the overall aim of improving the longterm health of consumers. Important targets include reducing the amounts of medium-chain saturated fatty acids, enhancing cis-9 18:1 to reduce cardiovascular risk, as well as increasing concentrations of trans-11 18:1 and cis-9, trans-11 18:2 which have been shown to exert ant...

Diet-induced milk fat depression (MFD) continues to have major economic impact in the dairy industry and a priority for finding solutions. Current thinking links MFD with the formation of bioactive trans fatty acid intermediates produced from biohydrogenation of unsaturated fatty acids by the rumen microbial population. The most potent biohydrogenation intermediates linked to MFD include severa...

Butyrivibrio fibrisolvens is the most active bacterial species in the biohydrogenation of polyunsaturated fatty acids (PUFA) in the rumen. It needs to remove the unsaturated bonds in order to detoxify the PUFA to enable the growth of the bacterium. Here, we investigated the response of cell membrane-associated proteins in B. fibrisolvens to growth in the presence of PUFA. Numerous changes were ...

Three experiments were conducted by in vitro incubations in ruminal fluid to investigate the effects of pH and amounts of linoleic and linolenic acids on the extent of their biohydrogenation, the proportions of conjugated linoleic acid (CLA) and trans-C18:1 as intermediates, and the ratio trans-10:trans-11 intermediates. The effects of pH and amount of linoleic acid were investigated in kinetic...

Dietary supplementation of stearidonic acid (SDA; 18:4n-3) has been considered a possible strategy to increase n-3 unsaturated fatty acid content in ruminant products; however, little is known about its metabolism in the rumen. In vitro batch incubations were carried out with bovine ruminal digesta to investigate the metabolism of SDA and its biohydrogenation products. Incubation mixtures (4.5 ...

in pasture-based milk production systems, using available farm resources in order to reduce feeding costs, the composition and functional properties of dairy cows’ milk are of considerable importance to the dairy farmer, manufacturer and consumer. basically, there are three options for altering the composition and/or functional properties of milk: 1) cow nutrition and grazing management, 2) cow...