Fatty acids in forages. II. In vitro ruminal biohydrogenation of linolenic and linoleic acids from timothy

The aim of this experiment was to, under typical Swedish production conditions, evaluate the effects of grass silages subjected to different N-fertilisation regimes fed to dairy cows on the fatty acid (FA) composition of their milk, and to compare the grass silages in this respect to red clover-dominated silage. Grass silages made from first year Phleum pratense L. leys subjected to three N-fertilisation regimes (30, 90 and 120 kg N/ha, designated G-30, G-90 and G-120, respectively) and a mixed red clover-grass silage (Trifolium pratense L. and P. pratense L.; 60/40 on dry matter (DM) basis, designated RC-G) were produced. The experiment was conducted as a change-over design, including 24 primiparous and multiparous dairy cows of the Swedish Red breed, each of which was allocated to three of the four diets. The cows were offered 11 kg DM of silage and 7 kg concentrates. The silages had similar DM and energy concentrations. The CP concentration increased with increase in N-fertilisation level. There was a linear increase in DM intake of the different silages with increased N fertilisation. There were also differences in concentrations of both individual and total FAs amongst silages. The daily milk production (kg/day) did not significantly differ between treatments, but G-30 silage resulted in higher concentrations of 18:2n-6 in the milk compared with the other two grass silages. The highest concentrations of 18:3n-3 and cis-9, trans-11 18:2 were found in milk from cows offered the RC-G silage. The G-30 diet resulted in higher concentration of 18:2n-6 and the same concentration of 18:3n-3 in the milk as the other grass silages, despite lower intake levels of these FAs. The apparent recoveries of 18:3n-3 from feed to milk were 5.74%, 4.27%, 4.10% and 5.31% for G-30, G-90, G-120 and RC-G, respectively. A higher recovery when red clover is included in the diet confirms previous reports. The higher apparent recovery of 18:3n-3 on the G-30 treatment may be related to the lower silage DM intake, which led to a higher relative proportion of ingested FAs originating from concentrates compared with the G-90 and G-120 diets. With the rates and types of concentrates used in this study, the achieved differences in FA composition among the silages were not enough to influence the concentrations of unsaturated FAs in milk.

Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 97%

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The effect of N-fertilisation rate or inclusion of red clover to timothy leys on fatty acid composition in milk of dairy cows fed a commercial silage : concentrate ratio

Arvidsson

Gustavsson

Fievez

et al. 2012

“…This indicates an effect of ensiling on rumen biohydrogenation. However, in contrast to what is generally accepted both in vitro (Boufaied et al, 2003b) as well as in vivo (French et al, 2000;Whiting et al, 2004), a lower biohydrogenation with ensiled compared with fresh forages was found in this study. Although, the explanation for this contradiction is not unambiguously clear, it might be linked to the presence in silages and to a lower extent in fresh or wiled forages of bound phenols.…”

Section: Silagescontrasting

confidence: 99%

Influence of damaging and wilting red clover on lipid metabolism during ensiling and in vitro rumen incubation

Ranst¹,

Fievez

Vandewalle³

et al. 2010

This paper describes the relationship between protein-bound phenols in red clover, induced by different degrees of damaging before wilting and varying wilting duration, and in silo lipid metabolism. The ultimate effect of these changes on rumen biohydrogenation is the second focus of this paper. For this experiment, red clover, damaged to different degrees (not damaged (ND), crushing or frozen/thawing (FT)) before wilting (4 or 24 h) was ensiled. Different degrees of damaging and wilting duration lead to differences in polyphenol oxidase (PPO) activity, measured as increase in protein-bound phenols. Treatment effects on fatty acid (FA) content and composition, lipid fractions (free FAs, membrane lipids (ML) and neutral fraction) and lipolysis were further studied in the silage. In FT, red clover lipolysis was markedly lower in the first days after ensiling, but this largely disappeared after 60 days of ensiling, regardless of wilting duration. This suggests an inhibition of plant lipases in FT silages. After 60 days of ensiling no differences in lipid fractions could be found between any of the treatments and differences in lipolysis were caused by reduced FA proportions in ML of wilted FT red clover. Fresh, wilted (24 h) after damaging (ND or FT) and ensiled (4 or 60 days; wilted 24 h; ND or FT) red clover were also incubated in rumen fluid to study the biohydrogenation of C18:3n-3 and C18:2n-6 in vitro. Silages (both 60 days and to a lower degree 4 days) showed a lower biohydrogenation compared with fresh and wilted forages, regardless of damaging. This suggests that lipids in ensiled red clover were more protected, but this protection was not enhanced by a higher amount of protein-bound phenols in wilted FT compared with ND red clover. The reduction of rumen microbial biohydrogenation with duration of red clover ensiling seems in contrast to what is expected, namely a higher biohydrogenation when a higher amount of FFA is present. This merits further investigation in relation to strategies to activate PPO toward the embedding of lipids in phenol-protein complexes.Keywords: polyphenol oxidase, fatty acid, PUFA, biohydrogenation, lipolysis ImplicationsRed clover polyphenol oxidase (PPO) has the potential to protect lipids against lipolysis in silage and lipolysis and biohydrogenation in the rumen, leading to higher concentrations of polyunsaturated fatty acids in ruminant meat and milk. PPO is a stress-activated enzyme, which is active in red clover. The goal of this paper was to study the effect of PPO activity due to damaging after mowing, measured as an increase in protein-bound phenols, and wilting duration on lipid metabolism in the silage, mainly lipolysis, and lipolysis and biohydrogenation in the rumen.

“…Several models have been suggested for the calculation of in vitro ruminal biohydrogenation and are often simplified, not taking all intermediates into account, as some are difficult to detect and quantify (Jenkins et al, 2008). Estimates of the rate of disappearance, calculated using values only for the one fatty acid observed, found under ruminal in vitro conditions exist for linolenic and linoleic acid in timothy (Boufaied et al, 2003), commercially available fat supplements (Carriquiry et al, 2008) and pure fatty acids and linseed oil (Jouany et al, 2007). The objective of the present study was to study the rate of ruminal biohydrogenation of unsaturated C18 fatty acids in ryegrass and red and white clover silages under in vitro conditions, calculated using a dynamic mechanistic model.…”

Section: Introductionmentioning

confidence: 99%

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

Lejonklev

Storm

Larsen

et al. 2013

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.