Ruminal biohydrogenation

Gonthier, C., Mustafa, A.F., Berthiaume, R., Petit, H.V., and Ouellet, D.R. 2004a. Feeding micro-ionized and extruded flaxseed to dairy cows Effects on digestion and ruminal biohydrogenation of long-chain fatty acids. Can. J. Anim. Sci. 84, 705-711. 

Petit, H.V., Tremblay, G.F., Tremblay, E., and Nadeau, P. 2002. Ruminal biohydrogenation of fatty acids, protein degradability, and dry matter digestibility of flaxseed treated with different sugar and heat combinations. Can. J. Anim. Sci. 82, 241-250. 

The fatty acids in milk fat are derived from two sources, de novo synthesis of fatty acids in the mammary gland and plasma lipids (see Pal-quist, Chapter 2). De novo synthesis generally involves short-chain and medium-chain fatty acids and some 16 0. The proportions of various fatty acids depend on the specific balance between enzymatic chain elongation and chain termination. The plasma lipids are derived from the diet and also from storage in the body tissues. For non-ruminants, the diet has a large influence on the fatty acid composition but for ruminants, biohydrogenation in the rumen results in much less impact of diet on the final fatty acids absorbed into the bloodstream. 

Ruminant milk fat is of unique composition among terrestrial mammals, due to its great diversity of component fatty acids. The diversity arises from the effects of ruminal biohydrogenation on dietary unsaturated fatty acids and the range of fatty acids synthesized de novo in the mammary gland. 

Future advances in the science of milk fat and nutrition will come from focusing on the unique biological properties of minor milk fatty acids arising from ruminal biohydrogenation and possibly some of de novo mammary origin. 

Incorporation of dietary unsaturated fat into milk fat by ruminants is low because of the efficient ruminal biohydrogenation process (Jenkins, 1993). Nevertheless, dietary fatty acids have profound effects on milk fat composition that have led to a prodigious amount of literature in the past 20 years (for reviews see Sutton, 1989 Grummer, 1991 Palmquist et al., 1993 Kennedy, 1996 Mansbridge and Blake, 1997 Chilliard et al., 2000, 2001). 

Several other procedures have been developed to protect unsaturated fatty acids from ruminal biohydrogenation. Of these, only the amide derivative has extensive research documentation (Jenkins, 1998, 1999), but has not been applied commercially. Often, calcium soaps of palm oil or canola fatty acids are referred to as protected. These are not protected from ruminal biohydrogenation (Table 2.2), but rather are ruminally inert with regard to their effects on the rumen microbial population. 

Figure 3.5. Generalized scheme of ruminal biohydrogenation of linoleic acid under normal conditions (solid line) and during diet-induced milk fat depression (dotted line). Adapted from Griinari and Bauman (1999).

Duckett, S. K., Andrae, J.G., Owens, F.N. 2002. Effect of high-oil corn or added corn oil on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets. J. Anim. Sci. 80, 3353-3360. 

Boufaied, H., Chouinard, P.Y., Tremblay, G.F., Petit, H.V., Michaud, R., and Belanger, G. 2003. Fatty acids in forages. II. In vitro ruminal biohydrogenation of linolenic and linoleic acids from... 

Troegeler-Meynadier, A., Nicot, M.C., Bayourthe, C., Moncoulon, R., and Enjalbert, F. 2003. Effects of pH and concentrations of linoleic and linolenic acids on extent and intermediates of ruminal biohydrogenation in vitro. J. Dairy Sci. 86, 4054-4063. 

Table 11.3 Major products of ruminant biohydrogenation of Ci8 unsaturated fatty acids...

Lundy III, FR, E. Block, W.C. Bridges, Jr., J.A. Bertrand, and T.C. Jenkins. Ruminal Biohydrogenation in Holstein Cows Fed Soybean Fatty Acids as Amides or Calcium Salts, T. Dairy Sci. 87 1038-1046 (2004). 

In contrast to cis-9, trans-11 and trans-1, cis-9, the other isomers of CLA found in milk and body fat of ruminants appear to originate exclusively from rumen output. These are detected in rumen fluid (61) and duodenal fluid (39), and estimates of duodenal flow indicate that rumen output of these minor cis/trans, cis-cis, and trans-trans CLA isomers is greater than the trace amounts secreted in milk fat (39). The common theme to endogenously synthesized CLA isomers is A -desaturase and the cis-9 double bond that is added to trans-1 and trans- 1 monoenes. In contrast, there has been no demonstration that other mammalian desaturases act in a manner analogous to A -desaturase to synthesize CLA endogenously from mono-unsaturated fatty acids. Thus, these other CLA isomers found in trace levels in ruminant fat are of rumen origin and must represent intermediates in the ruminal biohydrogenation of linoleic and linolenic acids. 

CLA, an intermediate in the ruminal biohydrogenation of linoleic acid to stearic acid (37), is present in highest concentrations in foods of ruminant origin (12). The predominant isomer of CLA present in beef is the cis-9,trans-ll isomer (38). Biohydrogenation of PUFA in the ramen significantly limits attempts to manipulate the fatty acid content of ruminant products. However, the CLA content of beef muscle is regulated mainly by the type of diet being fed and related mainly to the concentration of PUFA in the diet. 

Tannins were primarily considered as anti-nutritional biochemicals due to then-adverse effects on feed intake and nutrient utilization (Kumar and Vaithiyanathan 1990). Nevertheless in recent years, they have been recognized as nsefnl phytochemicals for beneficially modulating the rumen microbial fermentation. The effects of tannins on ruminant production have been published in the past, which primarily focused on the adverse effects of tannins on animal systan, with some discussion on their positive effects on protein metabolism and prevention of bloat (Mangan 1988 Kumar and Vaithiyanathan 1990 Aerts et al. 1999 Barry and McNabb 1999 McSweeney et al. 2001a Min et al. 2003 Mueller-Harvey 2006 Waghom 2008). This chapter focuses on the effects of tannins on ruminal microbial populations that affect N metabolism, methanogenesis and ruminal biohydrogenation process in the mmen. 

Manipulating Ruminal Biohydrogenation by the Use of Plants Bioactive Compounds... 

Keywords Ruminal biohydrogenation Conjugated linoleic acid Phytochemicals... 

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