Institut des Sciences de la Vie, Université catholique de Louvain, 2/8 Croix du Sud, B-1348 Louvain-la-Neuve, Belgium.
J Dairy Sci. 2011 Aug;94(8):4005-15. doi: 10.3168/jds.2011-4204.
Linseed and rapeseed, good sources of 18:3 n-3 and cis9-18:1, respectively, have been shown to improve the bovine milk fatty acid (FA) profile. However, rapeseed, unlike linseed, has little effect on the concentration of 18:3 n-3 in milk fat. Alfalfa protein concentrate (APC), besides being a valuable protein source for milk production, contains lipids rich in 18:3 n-3. Therefore, this experiment aimed at (1) evaluating the transfer efficiency of unsaturated FA (UFA), especially 18:3 n-3, of APC to bovine milk fat, and (2) evaluating whether extruded rapeseed (ER) associated with APC is as effective as extruded linseed (EL) in enhancing the bovine milk fat composition. Six lactating Holstein cows were used in a replicated 2 × 2 Latin square design with 2 iso-energy, iso-nitrogen and iso-FA corn silage-based diets (EL and ER-APC) and two 21-d periods. Extruded linseed, as main UFA source, was included in the first diet, whereas ER, as main UFA source, and APC, as supplemental 18:3 n-3, were included in the second diet. Diets were distributed as a restricted total mixed ration. Compared with the EL diet, the ER-APC diet, where ER was associated with APC, increased milk concentration of 18:3 n-3 (1.18 vs. 1.31% of FA) and cis9-18:1 (18.35 vs. 20.01% of FA). The apparent transfer efficiency of 18:3 n-3 from diet to milk was almost twice as much for the ER-APC diet than for the EL diet (7.4 vs. 3.8% of intake). Extruded linseed accounted for 84% of 18:3 n-3 provided in the EL diet, whereas ER and APC accounted for 33 and 38% of 18:3 n-3 provided in the ER-APC diet, respectively. Because both EL and ER underwent extrusion in similar conditions, these results suggest that 18:3 n-3 of EL in the EL diet and ER in the ER-APC diet were subjected to more extensive ruminal biohydrogenation than 18:3 n-3 of APC in the ER-APC diet. This experiment shows that corn silage-based diets supplemented with ER as the main UFA source, associated with APC as supplemental 18:3 n-3, are as effective as corn silage-based diets supplemented with EL as the main UFA source, in increasing bovine milk UFA and 18:3 n-3 contents. Furthermore, at similar levels of dietary incorporation, this experiment shows that the ruminal bypass of 18:3 n-3 is higher for APC compared with EL.
亚麻籽和油菜籽分别是 18:3n-3 和 cis9-18:1 的良好来源，已被证明可以改善奶牛乳脂肪酸（FA）谱。然而，与亚麻籽不同的是，油菜籽对乳脂肪中 18:3n-3 的浓度几乎没有影响。苜蓿蛋白浓缩物（APC）除了是牛奶生产的有价值的蛋白质来源外，还含有富含 18:3n-3 的脂质。因此，本实验旨在：（1）评估 APC 中非饱和脂肪酸（UFA），特别是 18:3n-3 的不饱和脂肪酸向奶牛乳脂肪中的传递效率；（2）评估与 APC 结合的膨化油菜籽（ER）是否与膨化亚麻籽（EL）一样有效地增强奶牛乳脂肪组成。在具有 2 个重复的 2×2 拉丁方设计中使用了 6 头泌乳荷斯坦奶牛，2 种基于玉米青贮的等能量、等氮和等 FA 日粮（EL 和 ER-APC）和 2 个 21 天期。膨化亚麻籽作为主要的 UFA 来源包含在第一种日粮中，而 ER 作为主要的 UFA 来源和 APC 作为补充 18:3n-3 则包含在第二种日粮中。日粮作为限制总混合日粮进行分配。与 EL 日粮相比，ER-APC 日粮中 ER 与 APC 结合，增加了乳中 18:3n-3 的浓度（1.18%对 FA 和 1.31%对 FA）和 cis9-18:1（18.35%对 FA 和 20.01%对 FA）。ER-APC 日粮中 18:3n-3 从日粮到乳中的表观传递效率几乎是 EL 日粮的两倍（7.4%对摄入的 3.8%）。EL 日粮中 18:3n-3 的 84%来自膨化亚麻籽，而 ER-APC 日粮中 18:3n-3 的 33%来自 ER 和 38%来自 APC。由于 EL 和 ER 均在相似条件下膨化，因此这些结果表明，EL 日粮中的 EL 和 ER-APC 日粮中的 ER 比 ER-APC 日粮中的 APC 中的 18:3n-3 经历了更广泛的瘤胃生物氢化。本实验表明，以 ER 作为主要 UFA 来源、与 APC 作为补充 18:3n-3 相结合的基于玉米青贮的日粮与以 EL 作为主要 UFA 来源的基于玉米青贮的日粮一样有效，能够增加奶牛乳 UFA 和 18:3n-3 的含量。此外，在相似的日粮添加水平下，本实验表明 APC 中 18:3n-3 的瘤胃旁路率高于 EL。
