Running Head: Linseeds and Fish Oil on Milk Fat in Goats Effect of Extruded Linseeds Alone or in Combination with Fish Oil on Intake, Milk Production, Plasma Metabolite Concentrations and Milk Fatty Acid Composition in Lactating Goats Inra-theix Introduction

26 Based on the potential benefits for long-term human health there is interest in 27 developing sustainable nutritional strategies for lowering medium-chain saturated 28 fatty acids (FA) and increasing specific unsaturated FA in ruminant milk. Dietary 29 supplements of extruded linseeds (EL), fish oil (FO) or a mixture of EL and FO 30 increase cis-9, trans-11 conjugated linoleic acid (CLA) and long-chain n-3 31 polyunsaturated FA in bovine milk. Supplements of FO cause milk fat depression 32 (MFD) in lactating cows, but information for dairy goats is limited. Fourteen Alpine 33 goats were used in a replicated 3 x 3 Latin square with 28 d periods to examine the 34 effects of EL alone or in combination with FO on animal performance, milk fat 35 synthesis and milk FA composition. Treatments comprised diets based on natural 36 grassland hay supplemented with no additional oil (control), 530 g/d of EL or 340 g/d 37 of EL and 39 g/d of FO (ELFO). Compared with the control, ELFO tended (P = 0.08) 38 to lower milk fat yield, whereas EL increased (P < 0.01) milk fat content and secretion 39 (15 and 10%, respectively). Relative to EL, ELFO decreased (P < 0.01) the 40 concentration and output of fat in milk (19 and 17%, respectively). Relative to the 41 control and ELFO, EL decreased (P < 0.05) milk 10:0-16:0 and odd-and branched-42 chain FA content and increased 18:0, cis-18:1, trans-∆ 13 18:1 (and their 43 corresponding ∆-9 desaturase products), trans-12,cis-14 CLA, cis-13,trans-15 CLA, 44 cis-12,trans-14 CLA and trans-11,cis-13 CLA and 18:3n-3 concentrations. ELFO was 45 more effective for enriching (P<0.05) milk cis-9,trans-11 CLA and trans-11 18:1 46 concentrations (up to 5.4-and 7.1-fold compared with the control) than EL (up to 1.7-47 and 2.5-fold increases). Furthermore, ELFO resulted in a substantial increase in milk 48 trans-10 18:1 concentration (5.4% total FA) with considerable variation between 49 individual animals. Relative to the control and EL, milk fat responses to ELFO were 50 3 characterized by increases (P < 0.05) in milk trans-16:1 (Δ9-11), trans-18:1 (Δ6-11), 51 trans-18:2, CLA (cis-9,trans-11, trans-9,cis-11, trans-8,trans-10 and trans-7,trans-9) 52 and 20-and 22-carbon FA concentrations. Overall, EL resulted in a relatively high 53 cis-9-18:1 concentration and an increase in the 18:3n-3/18:2n-6 ratio, whereas 54 combining EL and FO resulted in substantial increases in trans-FA, marginal 55 enrichment in 20:5n-3 and 22:6n-3, and lower 16:0 concentrations changes 56 associated with a …