Effects of high-sugar ryegrass silage and mixtures with red clover silage on ruminant digestion. 2. Lipids1

Abstract

The experiment investigated the digestion of lipids from different forage silages in beef steers. Six Hereford x Friesian steers prepared with rumen and duodenal cannulas were given ad libitum access to a high-sugar grass silage, control grass silage, red clover silage, or mixtures of the red clover and each of the grass silages (50:50, DM basis). The experiment was conducted as an incomplete 5 x 5 Latin square, with an additional randomly repeated sequence. Total fatty acid and C18:3n-3 concentrations were greater (P < 0.05) for the high-sugar grass silage than the control grass silage or the red clover silage. Dry matter and total fatty acid intake were less (P < 0.05) for steers fed the control grass silage than for steers fed the other diets. Duodenal flow of C18:3n-3 was greater (P < 0.05), and flows of C18:0 and total C18:1 trans were less (P < 0.05), for the red clover silage compared with the 2 grass silage diets, with the mixtures intermediate. These results were supported by a reduction (P < 0.05) in biohydrogenation of C18:3n-3 for the red clover silage, with the mixtures again being intermediate. Flows of total branched- and odd-chain fatty acids were greater (P < 0.05) for the high-sugar grass silage diet, possibly as a result of greater microbial flow, because these fatty acids are associated with bacterial lipid. Duodenal flows of the chlorophyll metabolite, phytanic acid, were greater (P < 0.05) for animals fed the high-sugar grass silage treatments compared with the other treatments. These results confirm the potential for modifying the fatty acid composition of ruminant products by feeding red clover silage.

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

“…Lee et al (2003) found in an in vitro experiment that a high inclusion of WSC in the diet induced a shift towards fermentation of WSC rather than fibre digestion, which suggests a shift away from fibrolytic bacteria. In contrast, there was no effect on C18 biohydrogenation when feeding high-sugar grass silage compared with a control silage (Lee et al, 2006). The higher concentration of 18:3n-3 in milk from cows offered the RC-G silage compared with the grass silages is in accordance with earlier studies.…”

The effect of high polyphenol oxidase grass silage on metabolism of polyunsaturated fatty acids and nitrogen across the rumen of beef steers1

“…The concentrations of fatty acids in the 3 silages are lower than typical reported values for ryegrass, red clover, and cocksfoot, although the proportions of individual fatty acids are comparable with the literature (Lee et al, 2006a;Dierking, 2008;Halmemies-Beauchet-Filleau et al, 2013). This may relate to the greater maturity (second cut) of the crops in the current study as shown by their fiber composition, as maturity is related to lower fatty acid content of herbage (Dewhurst et al, 2001).…”

“…This is consistent with net gain due to microbial fatty acid synthesis de novo in cattle fed diets containing low amounts of lipid, such as forage-only diets (Lee et al, 2006a;Halmemies-Beauchet-Filleau et al, 2013). The response was greater with CO as exemplified by a greater proportional increase in fatty acids associated with microbial lipids, namely C16:0 and BOC fatty acids (Vlaeminck et al, 2006).…”

“…There was an interaction effect (treatment × diet) for ruminal pH, with the grasses showing little change across the measurement period, whereas RC showed significant declines in pH associated with feeding. This typically reflects an ad libitum consumption pattern for the grasses where animals more typically grazed through the day (Lee et al, 2002), whereas the RC animals consumed the majority of the feed in 1 session after feeding, resulting in a drop in ruminal pH and a subsequent rise until the next feeding (Lee et al, 2006a). Volatile fatty acid concentrations in the rumen are similar to those previously reported from steers consuming grass or red clover silage (Merry et al, 2006).…”

“…When offered for ad libitum intake, legume silage typically shows greater levels of intake than grass silages in comparison studies due to greater digestibility of the former (Lee et al, 2006a;Kammes and Allen, 2012). In the current study, however, all silages were limited to 16 g DM/kg BW daily, which should equate to a range of intakes between 6.27 to 7.01 kg DM/d based on the mean and variance of animal BW.…”