The aim of this study was to characterize and determine how days in milk (DIM) affect the milk fatty acid (FA) profile of grazing donkeys. Donkey milk is very similar to human milk, containing bioactive molecules such as FA and proteins. However, there is a lack of scientific and technical information on the changes in the FA profile of asinine milk in pasture-feeding systems. Seven multiparous Pega donkeys, maintained in an exclusively extensive system, were used. Milking was undertaken twice a day, once a week for 16 weeks. Milk samples were composed according to the average lactating days as follows: 55, 110, 165, 220 and 275 DIM. A descriptive analysis of the milk fat composition was performed, and the linear and quadratic effects of DIM on the milk FA profile were tested. The milk FA profile of grazing donkeys is influenced by lactation days and is characterized by high concentrations of polyunsaturated FA (PUFA) with a low n−6 to n−3 ratio (0.66 g/100 g), mainly due to the high level of linolenic acid (16.8 g/100 g). Most of the individual FAs did not change during lactation, but stearic and oleic acid linearly decreased (p < .05), and total polyunsaturated FA (PUFA) and n−3 FA increased (p < .05) with DIM. The milk profile of grazing donkeys is influenced by the day of lactation and is characterized by a high concentration of n−3 PUFA (mainly α-linolenic acid) and a lower n−6 to n−3 ratio. As the number of days of lactation increased, the concentration of n−3 PUFA also increased. Therefore, higher milk quality may be associated with higher days in milk.

中文翻译：

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牛奶中的天数改变了放牧驴的牛奶脂肪酸谱：一项初步研究

本研究的目的是表征和确定牛奶中的天数 (DIM) 如何影响放牧驴的牛奶脂肪酸 (FA) 谱。驴奶与人奶非常相似，含有生物活性分子，如 FA 和蛋白质。然而，缺乏关于牧场饲养系统中 asinine 牛奶 FA 特征变化的科学和技术信息。使用了七头经产的 Pega 驴，饲养在一个专门广泛的系统中。每天挤奶两次，每周一次，持续 16 周。牛奶样品根据平均泌乳天数组成如下：55、110、165、220 和 275 DIM。对乳脂成分进行了描述性分析，并测试了 DIM 对牛奶 FA 曲线的线性和二次影响。放牧驴的牛奶 FA 谱受泌乳天数的影响，其特点是高浓度的多不饱和脂肪酸 (PUFA) 和低 n-6 与 n-3 的比率 (0.66 g/100 g)，主要是由于高水平的亚麻酸（16.8 克/100 克）。大多数个体 FA 在哺乳期间没有变化，但硬脂酸和油酸线性下降（p  < .05)，并且总多不饱和脂肪酸 (PUFA) 和 n-3 FA 随 DIM增加 ( p < .05)。放牧驴的乳汁成分受泌乳日的影响，其特点是高浓度的 n-3 PUFA（主要是 α-亚麻酸）和较低的 n-6 与 n-3 比率。随着泌乳天数的增加，n-3 PUFA 的浓度也增加。因此，较高的牛奶质量可能与较高的牛奶天数有关。