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

Abstract

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.

Effect of legume–grass silages and α-tocopherol supplementation on fatty acid composition and α-tocopherol, β-carotene and retinol concentrations in organically produced bovine milk

“…The recoveries on the two red clover diets in Exp. 1 was similar to results reported by Dewhurst et al (2003b) and Arvidsson et al (2012) for cows on red clover-grass silage. However, the recovery of C18:3n-3 on S3 in Exp.…”

“…This result is found in several previous studies (e.g. Arvidsson et al, 2012;Dewhurst et al, 2003b;Jayanegara et al, 2011), and one suggested explanation are a higher ruminal disappearance the more double bounds that are present in the FA.…”

Fatty acid concentrations in timothy (Phleum pratenseL.) and meadow fescue (Festuca pratensisHuds.): Effects of seasonal variations at different nitrogen fertilization levels

“…Similarly, Elgersma et al (2005) found higher concentrations of individual FAs and TFA for treatments involving higher levels of added N. However, the latter authors did not find any fertilization-related differences in the relative proportions of the different FAs, which is consistent with the results obtained in this work (Table II). In a study with similar N-fertilization levels as in this work, Arvidsson et al (2012) observed the highest TFA concentration in grass fertilized with 90 kg N ha (1 , the lowest in grass fertilized with 30 kg N ha (1 , and an intermediate TFA concentration in grass fertilized with 120 kg N ha (1 .…”

Milk production from silage: comparison of grass, legume and maize silages and their mixtures

“…Vanhatalo et al (2007) showed a greater increase in 18:3 content of milk fat for early-cut red clover silage in comparison with late-cut red clover silage. Dewhurst et al (2003b) observed intermediate levels of 18:3 in milk when feeding mixtures of grass silage and red clover silage; Arvidsson et al (2012) found only small but statistically significant increases when feeding a mixture of timothy and red clover silage.…”