The first secretion, 24-h post parturition of the mammary glands of sows, known as colostrum, is high in protein and low in lactose and fat. As a consequence of an insufficient ingestion of colostrum, more than 50% of piglets fail to reach weaning and die. The composition and some functions of colostrum have been previously reported. For example, colostrum carbohydrates consist of mainly lactose. Lipids in the colostrum are mostly triacylglycerols, but <1% is fatty acids, which may act as homeostasis regulators. Similarly, proteins are found mostly as casein and whey, the latter being ≥80% immunoglobulins. Colostrum-derived immunoglobulins and bioactive proteins such as azurocidin help the immune system of the piglet fend off infections. In addition, leukocytes and exosomes are other minor but nonetheless equally crucial bioactive components in the porcine colostrum. Modern pig farming has achieved increases in pig productivity and litter size, but this has been accomplished in detriment of the health and the survival rate of piglets. Therefore, porcine colostrum is now even more important in pig farming. In the present review, we discuss the current knowledge on the composition and physiological functions of the porcine colostrum and briefly propose future research directions.

中文翻译：

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猪初乳的成分及生理功能

母猪分娩后 24 小时乳腺的第一种分泌物称为初乳，其蛋白质含量高，乳糖和脂肪含量低。由于初乳摄入不足，超过 50% 的仔猪无法断奶而死亡。初乳的成分和一些功能以前已有报道。例如，初乳碳水化合物主要由乳糖组成。初乳中的脂质主要是三酰甘油，但<1% 是脂肪酸，它可以作为稳态调节剂。同样，蛋白质主要以酪蛋白和乳清的形式存在，后者是 ≥ 80% 的免疫球蛋白。初乳衍生的免疫球蛋白和生物活性蛋白（如天青素）有助于仔猪的免疫系统抵御感染。此外，白细胞和外泌体是猪初乳中其他次要但同样重要的生物活性成分。现代养猪业提高了猪的生产力和窝产仔数，但这却损害了仔猪的健康和存活率。因此，猪初乳现在在养猪业中显得尤为重要。在本综述中，我们讨论了目前关于猪初乳的成分和生理功能的知识，并简要提出了未来的研究方向。