Effect of substituting fresh-cut perennial ryegrass with fresh-cut white clover on bovine milk fatty acid profile

Abstract

Background: Including forage legumes in dairy systems can help address increasing environmental/economic concerns about perennial ryegrass monoculture pastures. This work investigated the effect of substituting fresh-cut grass with increasing quantities of fresh-cut white clover (WC) on milk fatty acid (FA) profile and transfer efficiency of dietary linoleic (LA) and α-linolenic (ALNA) acids to milk fat. Three groups of three crossbred dairy cows were used in a 3 × 3 crossover design. Dietary treatments were 0 g kg^-1 WC + 600 g kg^-1 grass, 200 g kg^-1 WC + 400 g kg^-1 grass, and 400 g kg^-1 WC + 200 g kg^-1 grass. All treatments were supplemented with 400 g kg^-1 concentrates on a dry matter basis. Cows had a 19-day adaptation period to the experimental diet before a 6-day measurement period in individual tie stalls.

Results: Increasing dietary WC did not affect dry matter intake, milk yield or milk concentrations of fat, protein or lactose. Milk polyunsaturated FA concentrations (total n-3, total n-6, LA and ALNA) and transfer efficiency of LA and ALNA were increased with increasing dietary WC supply.

Conclusion: Inclusion of WC in pastures may increase concentrations of nutritionally beneficial FA, without influencing milk yield and basic composition, but any implications on human health cannot be drawn. © 2018 The Authors. Journal of the Science of Food and Agriculture published by JohnWiley & Sons Ltd on behalf of Society of Chemical Industry.

Keywords: dairy cows; fresh-cut grass; milk fatty acids; transfer efficiency; white clover.

Figure 1

Interaction means ± SE (shown as error bars) for the effects of dietary treatment (white clover (WC) offered on a dry matter basis (Control, 0 g kg⁻¹, white bars; Low‐WC, 200 g kg⁻¹, grey bars; High‐WC, 400 g kg⁻¹, black bars) and experimental period on the transfer efficiency (g kg⁻¹ intake) of dietary c9c12 C18:2 (LA, linoleic acid) to milk fat over the three experimental periods of the feeding trial. Bars labelled with different letters are significantly different (P < 0.05) according to Fisher's least significant difference test.

Figure 2

Relationships between white clover dry matter intake (DMI) and transfer efficiencies (g kg⁻¹ intake) of c9c12 C18:2 (LA, linoleic acid) and c9c12c15 C18:3 (ALNA, α‐linolenic acid), assessed in individual tie‐stalls with lactating dairy cows over the three experimental periods of the feeding trial. R ² and P represent pseudo‐correlation coefficient and ANOVA P‐value, respectively. Values in parentheses represent SE.

Figure A1

Interaction means ± SE (shown as error bars) for the effects of the interaction between dietary treatment (white clover (WC) offered on a dry matter basis (Control, 0 g kg⁻¹, white bars; Low‐WC, 200 g kg⁻¹, grey bars; High‐WC, 400 g kg⁻¹, black bars) and experimental period on the milk concentrations of monounsaturated fatty acids (MUFA), C16:0, c9 C18:1 (OA, oleic acid) and Δ⁹‐desaturase activity index (Δ⁹I), over the three experimental periods of the feeding trial. P represents the ANOVA P‐value for the interaction.