Dairy Science and Technology Group of Food Quality and Design (FQD), Wageningen University and Research, PO Box 17, 6700 AA, Wageningen, the Netherlands.
Animal Nutrition Group, Wageningen University and Research, PO Box 338, 6700 AH, Wageningen, the Netherlands.
J Dairy Sci. 2022 Apr;105(4):2828-2839. doi: 10.3168/jds.2021-21083. Epub 2022 Feb 16.
The aim of this study was to analyze the effect of fat and protein supplementation to dairy cattle rations on milk fat triacylglycerol (TAG) composition, fatty acid (FA) positional distribution in the TAG structure, and milk solid fat content (SFC). Fifty-six lactating Holstein-Friesian cows were blocked into 14 groups of 4 cows and randomly assigned 1 of 4 dietary treatments fed for 28 d: (1) low protein, low fat, (2) high protein, low fat, (3) low protein, high fat, and (4) high protein, high fat. The high protein and high fat diets were obtained by isoenergetically supplementing the basal ration (low protein, low fat) with rumen-protected soybean meal and rumen-protected rapeseed meal, and hydrogenated palm FA (mainly C16:0 and C18:0), respectively. Fat supplementation modified milk TAG composition more extensively compared with protein supplementation. Fat supplementation resulted in decreased concentrations of the low molecular weight TAG carbon number (CN) 26 to CN34 and medium molecular weight TAG CN40, CN44, and CN46, and increased concentrations of CN38 and the high molecular weight TAG CN50 and CN52. Increased contents of C16:0, C18:0, and C18:1cis-9 in TAG in response to fat supplementation were related to increases in the relative concentrations of C16:0 and C18:0 at the sn-2 position and C18:0 and C18:1cis-9 at the sn-1(3) positions of the TAG structure. Increased concentrations of high molecular weight TAG species CN50 and CN52 in response to fat supplementation was associated with increased milk SFC at 20, 25, and 30°C. Our study shows that important alterations in milk TAG composition and structure occur when feeding hydrogenated palm FA to lactating dairy cattle, and that these alterations result in an increased SFC of milk fat. These changes in milk SFC and TAG composition and structure may improve absorption of both fat and minerals in milk-based products for infants and may affect processing of milk fat.
本研究旨在分析奶牛日粮中添加脂肪和蛋白质对乳脂三酰基甘油(TAG)组成、TAG 结构中脂肪酸 (FA)位置分布以及乳脂固体脂肪含量 (SFC)的影响。将 56 头泌乳荷斯坦-弗里森奶牛分为 14 个 4 头奶牛的组块，并随机分配到 4 种日粮处理中的 1 种，每种日粮处理饲喂 28d：（1）低蛋白、低脂肪，（2）高蛋白、低脂肪，（3）低蛋白、高脂肪，（4）高蛋白、高脂肪。高蛋白和高脂肪日粮是通过在基础日粮（低蛋白、低脂肪）中分别添加瘤胃保护性大豆粕和瘤胃保护性油菜籽粕以及氢化棕榈 FA（主要是 C16:0 和 C18:0）来获得的。与蛋白质添加相比，脂肪添加更广泛地改变了乳脂 TAG 组成。脂肪添加导致低分子量 TAG 碳数 (CN)26 至 CN34 和中分子量 TAG CN40、CN44 和 CN46 的浓度降低，而 CN38 和高分子量 TAG CN50 和 CN52 的浓度增加。TAG 中 C16:0、C18:0 和 C18:1cis-9 含量的增加与 TAG 结构中 sn-2 位置的 C16:0 和 C18:0 以及 sn-1(3)位置的 C18:0 和 C18:1cis-9 相对浓度的增加有关。脂肪添加导致的高分子量 TAG 物种 CN50 和 CN52 浓度的增加与 20、25 和 30°C 时乳脂 SFC 的增加有关。本研究表明，给泌乳奶牛饲喂氢化棕榈 FA 会导致乳脂 TAG 组成和结构发生重要变化，从而导致乳脂 SFC 增加。乳脂 SFC 和 TAG 组成和结构的这些变化可能会改善婴儿配方奶中脂肪和矿物质的吸收，并可能影响乳脂的加工。
