Yield, composition, and fatty acid profile of milk from Anglo Nubian goats fed a diet supplemented with vegetable oils

ABSTRACT We aimed to evaluate the inclusion of three sources of vegetable oil in the diet of lactating goats on production in 120 days of lactation and the effect of these sources and lactation stage on fortnightly composition and fatty acid profile of goat milk at 20, 50, 80, and 110 days of lactation. A completely randomized design was adopted and 32 Anglo Nubian goats were used, distributed in four treatments: control diet and diets with inclusion of 30 g/kg of dry matter of diet of canola, sunflower, or soybean oil. The dairy production was 182.75 kg, and there was no difference for treatments. Among the constituents, only urea nitrogen was influenced by treatment and presented lower content for control treatment. Day of lactation had an effect on lactose. Defatted dry extract and somatic cell count had a quadratic effect with minimum values around 100 and 33 days of lactation, respectively. The content of urea nitrogen, also with a quadratic effect, was higher at 93 days of lactation. For protein, there was an interaction between treatments and period and, at the end of lactation, its content was increased. The inclusion of vegetable oils promoted reduction in total saturated fatty acids (SFA) and increased the total content of monounsaturated fatty acids (MUFA) and conjugated linoleic acid. The proportions MUFA:SFA and PUFA:SFA, the atherogenicity and thrombogenicity indexes, and the relation hypocholesterolemic fatty acids:hypercholesterolemic fatty acids improved with oil addition in animal diets. The addition of vegetable oil to diets for lactating goats improve the fatty acid profile with no impairment on milk production and composition, and the milk from early stages of lactation has better nutritional quality of the lipid fraction.摘要 本研究旨在评估泌乳山羊日粮中添加三种植物油源对120天泌乳期产奶量的影响，以及这些油源和泌乳阶段对泌乳第20、50、80、110天时山羊乳每两周的乳组成及脂肪酸谱的影响。本试验采用完全随机设计，选用32只安格鲁努比亚山羊，将其随机分为4个处理组：对照组日粮，以及日粮干物质中添加30 g/kg菜籽油、葵花籽油或大豆油的试验日粮。试验期总产奶量为182.75 kg，各处理组间产奶量无显著差异。在各项乳成分指标中，仅尿素氮含量受处理组影响，对照组的尿素氮水平更低。泌乳天数对乳糖含量存在显著影响。脱脂干固形物与体细胞数（somatic cell count, SCC）均呈二次变化趋势，其最低值分别出现在泌乳第100天和第33天左右。尿素氮含量同样呈二次变化趋势，在泌乳第93天时达到峰值。乳蛋白含量存在处理组与采样周期的交互作用，且泌乳末期乳蛋白含量有所升高。日粮添加植物油可降低总饱和脂肪酸（SFA）的含量，同时提升总单不饱和脂肪酸（MUFA）与共轭亚油酸（conjugated linoleic acid, CLA）的含量。单不饱和脂肪酸与饱和脂肪酸比值（MUFA:SFA）、多不饱和脂肪酸（polyunsaturated fatty acids, PUFA）与饱和脂肪酸比值（PUFA:SFA）、致动脉粥样硬化指数、致血栓形成指数，以及降胆固醇脂肪酸与升胆固醇脂肪酸的比值，均随日粮中植物油的添加得到优化。向泌乳山羊日粮中添加植物油可改善乳脂肪酸谱，且不会对产奶量及乳成分造成负面影响，泌乳早期山羊乳的脂质组分具备更优的营养品质。