ABSTRACT Leptin is a protein hormone secreted by white adipose tissue, and variation in leptin gene (LEP) has been described to affect milk production traits in different cattle breeds. The purpose of this study was to investigate whether nucleotide sequence variations identified in exon 3 of LEP were the same as those reported previously, and ascertain whether the variations detected affected milk traits in New Zealand (NZ) Holstein-Friesian × Jersey-cross (HF×J-cross) cows. Polymerase Chain Reaction – Single Strand Conformation Polymorphism (PCR-SSCP) analysis coupled with nucleotide sequencing, enabled 443 HF×J-cross dairy cows to be studied. The PCR-SSCP and nucleotide sequencing revealed three variant sequences (A, B and C), with a total of five single-nucleotide substitutions. There were no associations revealed between LEP genotypes and milk yield and fat percentage. However, cows carrying the AB genotype had a decreased percentage of protein in their milk. This is the first time such findings in NZ HF×J-cross cows have been reported, and they suggest that variation in exon 3 of LEP may be useful for selecting cows for improvement in key milk traits.

中文翻译：

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牛瘦素基因变异对新西兰荷斯坦-弗里斯兰×泽西杂交奶牛产奶性状的影响

摘要 瘦素是一种由白色脂肪组织分泌的蛋白质激素，瘦素基因 (LEP) 的变异已被描述为影响不同牛品种的产奶性状。本研究的目的是调查 LEP 外显子 3 中鉴定的核苷酸序列变异是否与之前报道的相同，并确定检测到的变异是否影响新西兰 (NZ) Holstein-Friesian × Jersey-cross (HF ×J-cross) 奶牛。聚合酶链反应——单链构象多态性 (PCR-SSCP) 分析与核苷酸测序相结合，使 443 头 HF×J 杂交奶牛得以研究。PCR-SSCP 和核苷酸测序揭示了三个变异序列（A、B 和 C），总共有五个单核苷酸替换。LEP 基因型与产奶量和脂肪百分比之间没有关联。然而，携带 AB 基因型的奶牛其牛奶中的蛋白质百分比降低。这是新西兰 HF×J 杂交奶牛的此类发现首次被报道，他们表明 LEP 外显子 3 的变异可能有助于选择奶牛以改善关键牛奶性状。