EFFECTS OF HIGH SOYBEAN OIL FOR GOATS IN LATE LACTATION ON INTAKE, MILK COMPOSITION AND FATTY ACID PROFILE

Abstract

Animal fat and vegetable oils are generally added to livestock diets to increase energy density. Unlike other ruminants, goats can tolerate more than 6% dietary fat. Feeding a diet containing soybean oil (SO), rich in polyunsaturated fatty acids (PUFA) to goats can change the milk fat composition, thereby modifying the nutritional quality of the milk. PUFA such as linoleic acids are considered healthier fats since they have been shown to reduce the risk of cardiovascular diseases in humans. Eighteen dairy goats (3 - 4 yr.; BW = 40 kg; 9 Saanen and 9 Alpine) in late lactation were used in an experiment to determine the effect of high PUFA (12% soybean oil; 12% SO) on feed intake, milk composition and fatty acid profile. Does were group fed once a day (2 pens per treatment) a 16% CP and 3.5 Mcal DE/kg diets containing either 6 or 12% SO for 24 d. Feed intake was recorded daily during the trial and milk yield was recorded from d-10 to d-24. Milk samples were collected 3 times a week and analyzed for protein, fat, lactose, and total solids. Milk fat was extracted and prepared for fatty acid methyl esters (FAME). The FAMEs were analyzed using a gas chromatography (GC) unit, fitted with a 60 m x 0.25 mm i.d. fused silica SP 2380 (Sigma-Aldrich) capillary column. The data were analyzed using MIXED procedures in SAS as a completely randomized design with repeated measures. Dietary treatments did not affect (P > 0.05) pen feed intake, milk yield or milk composition (fat, protein, lactose and total solids). Diet containing 12% SO decreased (P < 0.05) the proportion of saturated fatty acids (SFA; C6:0, C8:0, C10:0, C12:0, C14:0, C16:0) and increased (P < 0.01) the proportions of monounsaturated fat (MUFA; C18:1n9; C18:1t), and the predominant PUFA, linoleic acid (C18:2n6). The results indicate that goats consuming diet with 12% SO (high PUFA) in late lactation produced milk with higher proportions of PUFA and MUFA and lower proportions of SFA compared to 6% SO.