Ruminants Feed into Milk

Hristov AN University of Idaho This proposal seeks, through dietary means, better capture of ruminal ammonia-nitrogen into microbes and consequently into milk. This will increase the efficiency of utilization of feed N and reducing N excretions in the dairy cow. NRI comp. grant... 

Gulati, S.K., Kitessa, S.M., Ashes, J.R., Fleck, E., Byers, E.B., Byers, Y.G., and Scott, T.W. (2000) Protection of Conjugated Linoleic Acids from Ruminal Hydrogenation and Their Incorporation into Milk Fat, Anim. Feed Sci. Technol. 86,139-148. 

T. W. (2000) Protection of Conjugated Linoleic Acids from Ruminal Hydrogenation and Their Incorporation into Milk Fat, Anim. Feed Sci. Technol. 86, 139-148. 

Several studies achieved in enviromnental conditions have shown that PAHs can be excreted in the milk of ruminants when feeded with PAHs [306]. The authors concluded there was an excretion of PAHs into milk under native forms when rumiants were fed with low PAHs content. However, a slight increase in concentration could induce the metabolism, which should lead to an increase in the excretion of metabolites into the milk. In spite of the absence of a significant transfer of parent PAHs to milk, the appearance of metabolites in milk raises questions of their impact on human health. 

Various sources of lipid have been incorporated into ruminant diets to increase the energy density and provide the large amount of energy needed for slaughter animals to achieve market weight or for dairy cows to produce milk (see Milk and milkproducts). Fats also reduce the dustiness of feeds, increase the feedstuffs abiUty to pellet, and improve feed acceptabiUty. 

Marine lipids with their diversity of unsaturated and branched chain acid moieties are a difficult class of materials to analyze. Ruminants (sheep, goats, cows, etc.) have a bacterial "factory" in the rumen which is able to produce branched-chain partially-hydrogenated lipids from ingested plant lipids. These lipids are incorporated into the milk and meat of the animals and eventually into animals which feed upon the ruminants. As a rule animal lipids are highly complex in comparison to plant materials. Although the branched chain materials are usually present in low concentration when compared to the common fatty acid moieties, complete description of these fats requires more sophisticated GC and thus long open tubular columns in tandem with mass spectrometry and computer analysis of the data has become an important approach. Even with a 100-m column, subcutaneous lipids of barley-fed lambs were so complex that prior fractionation with urea adducts was necessary (17). 

Based on a meta-analysis of 32 studies Broderick et al. (2010) concluded that the omasal canal non ammonia-N flows were equal to N intake at ruminal ammonia concentration of 5.1 mmol/l and milk urea concentration of 17.8 mg/100 ml. Under such circumstances there is no net absorption of ammonia from the rumen but the amount of protein degraded in the rumen equals the microbial N synthesis. Based on the above mentioned criteria ruminal ammonia concentrations were critically low on all urea infusion levels in the current study. In spite of low ruminal ammonia-N concentrations the major proportion (0.67) of urea-N infused into the rumen was excreted in urine suggesting that the rumen microbes couldn t completely utilize extracellular ammonia-N under limiting conditions. The current flndings indicate that the microbial N synthesis was more sensitive to moderately low ruminal ammonia N concentrations than fibre digestion because intraruminal urea infusions seemed to increase microbial N synthesis but no effect was observed in fibre digestion or feed intake. 

Kitessa, S.M., D. Peake, R. Bencini and A.J. Williams, 2003. Fish oil metabolism in ruminants III. Transfer of n-3 polyunsaturated fatty acids (PUFA) from tuna oil into sheep s milk. Anim. Feed Sci. Tech. 108,1-14. 

Kitessa, S.M., S.K.Gulati, J.R. Ashes, E. Fleck, T.W. Scott and P.D. Nichols, 2001. Utilisation of fish oil in ruminants. II. Transfer of flsdh oil fatty acids into goat s milk. Anim. Feed Sci. Tech. 89, 201-208. 

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