Differences in rate of ruminal hydrogenation of C18 fatty acids in clover and ryegrass

Abstract

Biohydrogenation of C18 fatty acids in the rumen of cows, from polyunsaturated and monounsaturated to saturated fatty acids, is lower on clover than on grass-based diets, which might result in increased levels of polyunsaturated fatty acids in the milk from clover-based diets affecting its nutritional properties. The effect of forage type on ruminal hydrogenation was investigated by in vitro incubation of feed samples in rumen fluid. Silages of red clover, white clover and perennial ryegrass harvested in spring growth and in third regrowth were used, resulting in six silages. Fatty acid content was analysed after 0, 2, 4, 6, 8 and 24 h of incubation to study the rate of hydrogenation of unsaturated C18 fatty acids. A dynamic mechanistic model was constructed and used to estimate the rate constants ( k, h) of the hydrogenation assuming mass action-driven fluxes between the following pools of C18 fatty acids: C18:3 (linolenic acid), C18:2 (linoleic acid), C18:1 (mainly vaccenic acid) and C18:0 (stearic acid) as the end point. For k C18:1,C18:2 the estimated rate constants were 0.0685 (red clover), 0.0706 (white clover) and 0.0868 (ryegrass), and for k C18:1,C18:3 it was 0.0805 (red clover), 0.0765 (white clover) and 0.1022 (ryegrass). Type of forage had a significant effect on k C18:1,C18:2 ( P , 0.05) and a tendency to effect k C18:1,C18:3 ( P , 0.10), whereas growth had no effect on k C18:1,C18:2 or k C18:1,C18:3 ( P . 0.10). Neither forage nor growth significantly affected k C18:0,C18:1 , which was estimated to be 0.0504. Similar, but slightly higher, results were observed when calculating the rate of disappearance for linolenic and linoleic acid. This effect persists regardless of the harvest time and may be because of the presence of plant secondary metabolites that are able to inhibit lipolysis, which is required before hydrogenation of polyunsaturated fatty acids can begin.Keywords: clover, fatty acids, hydrogenation, ruminal, ryegrass ImplicationsEfforts are being made to improve ruminal foods, such as meat and milk, to make them more beneficial for human health. Fat content, with regard to saturated and unsaturated fats, has received a lot of attention. In the present study, the effects of red and white clover silages on fatty acid metabolism in the cow rumen were studied in vitro. Both types of clover silages were found to have similar effects on the fatty acid metabolism, which could potentially be used to determine feed types that could increase concentrations of unsaturated fatty acids in milk.

An update to the fatty acid profiles of bovine retail milk in the United Kingdom: Implications for nutrition in different age and gender groups

“…In winter, grass/clover silage commonly used in ORG systems when pasture is not available, has been found to increase ALNA concentrations when compared with grass or grass/maize silage (Dewhurst, Fisher, Tweed, & Wilkins, 2003;Wiking, Theil, Nielsen, & Sorensen, 2010), commonly used in the CON systems. This may be explained by the slower DM degradation (Dewhurst, Evans, Scollan, Moorby, Merry, & Wilkins, 2003) and rates of RBH of clover compared with grass (Lejonklev, Storm, Larsen, Mortensen, & Weisbjerg, 2013), which may increase rumen passage rates, reduce RBH of ALNA, and eventually increase transfer rates of dietary ALNA to milk. In humans and animals, including cattle, ALNA is used as substrate for the synthesis of EPA and DPA by various enzymes, including elongases, Δ 5 -desaturase and Δ 6 -desaturase ( Barcelo-Goblijn, et al, 2009).…”

A 2-year study on milk quality from three pasture-based dairy systems of contrasting production intensities in Wales

“…Milk from both OM and CL systems showed more desirable FA profiles than CH milk, but there were also differences between these two systems. For example, CL milk was higher in VA and RA compared with OM milk, possibly reflecting the higher pasture intake on CL farms (Butler et al 2008) exacerbated by lower rates of hydrogenation (less VA production) associated with clover inclusion in the OM swards (Dewhurst et al 2009;Lee et al 2009;Lejonklev et al 2013). This finding is particularly interesting because Stergiadis et al (2012) reported that raising pasture intake from 200 to 370 g/kg of DMI throughout the year did not have a significant impact on VA and RA contents of milk but a similar increase (albeit from a much higher baseline) in pasture intake in the present study (700 g/kg DMI for OM v. 840 g/kg DMI on CL farms) did significantly raise milk VA and RA concentrations by 21 and 28%, respectively.…”

Immune and oxidative response to linseed in the diet of periparturient Holstein cows

“…Extensive research with dietary n-3 fatty acid sources has focused on changing milk fatty acid composition (Shingfield et al, 2005;Lejonkleva et al, 2013;Nudda et al, 2013;Gallardo et al, 2014), disregarding the effect of n-3 fatty acids on the immune system or oxidative stress in dairy cows. The aim of this research was to determine the influence of dietary replacement of n-6 with n-3 polyunsaturated fatty acids (PUFA) on cellular immunity and oxidative stress in the transition period of dairy cows.…”