ABSTRACT An amino acid substitution (K232A) in the enzyme diacylglycerol acyl-CoA acyltransferase 1 (DGAT1) has been reported to explain variation in milk traits and milk fatty acid (FA) profile. In this study, associations between K232A, and milk traits including milk FA composition, were studied in wholly pasture-fed New Zealand Holstein-Friesian × Jersey cross-bred (KiwicrossTM) dairy cows. With a high frequency of K variant (61.9%), the KK cows produced more milk fat on average (5.41 ± 0.04%), than the AA cows (4.43 ± 0.06%). The milk volume, fat concentration and protein concentration for the AK cows were between the values for the genotypes AA and KK. More C16 : 0 (saturated fatty acid), conjugated linoleic acid (CLA) and polyunsaturated fatty acid (C18:3 cis-9, 12, 15) were found in the milk of the KiwicrossTM cows, and the influence of DGAT1 K232A on these FAs during the mid- and late- stage of lactation were significant. The AA cows produced more (P < 0.001) CLA (1.137 ± 0.047 g/100 g) and C18:3 cis-9, 12, 15 (0.855 ± 0.015 g/100 g), but less C16:0 (35.170 ± 0.355 g/100 g) than the KK cows (0.934 ± 0.025 g/100 g, 0.778 ± 0.009 g/100 g and 38.010 ± 0.250 g/100 g respectively).

中文翻译：

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DGAT1变异体（K232A）对户外放牧奶牛乳性状和乳脂组成的影响

摘要 据报道，二酰基甘油酰基辅酶 A 酰基转移酶 1 (DGAT1) 中的氨基酸取代 (K232A) 可以解释牛奶性状和牛奶脂肪酸 (FA) 谱的变化。在这项研究中，K232A 与牛奶特性（包括牛奶 FA 成分）之间的关联在完全牧场喂养的新西兰荷斯坦 - 弗里斯兰 × 泽西杂交 (KiwicrossTM) 奶牛中进行了研究。由于 K 变异的高频率 (61.9%)，KK 奶牛的平均乳脂 (5.41 ± 0.04%) 比 AA 奶牛 (4.43 ± 0.06%) 多。AK 奶牛的牛奶体积、脂肪浓度和蛋白质浓度介于基因型 AA 和 KK 的值之间。在 KiwicrossTM 奶牛的牛奶中发现了更多 C16:0（饱和脂肪酸）、共轭亚油酸 (CLA) 和多不饱和脂肪酸（C18:3 cis-9, 12, 15），DGAT1 K232A 对泌乳中后期这些 FAs 的影响是显着的。AA 奶牛产生更多 (P < 0.001) CLA (1.137 ± 0.047 g/100 g) 和 C18:3 cis-9, 12, 15 (0.855 ± 0.015 g/100 g)，但更少 C16:0 (35.155 ± 0.3) g/100 g）比 KK 奶牛（分别为 0.934 ± 0.025 g/100 g、0.778 ± 0.009 g/100 g 和 38.010 ± 0.250 g/100 g）。