How the milk chemical composition and fatty acid profile are influenced by physiological factorsin Najdi dairy sheep

Sheep milk production is a complex process that is influenced by various factors. This study aims to investigate how the litter size (single vs. twins), birth type (male vs. female), age of the ewes and body weight affect the milk composition and fatty acid profile of milk fat. Milk samples were collected from 119 Najdi ewes that were the subject of this study. Gas chromatography-mass spectrometry (GC-MASS) was used to quantify the fatty acids (FAs). The results showed that the twins birth type (female/female) has a significant influence (P < 0.05) on the concentration of linoleic acid (LA), alpha-linolenic acid (ALA), behenic acid (C22:0) and polyunsaturated fatty acid (PUFA). On the other hand, saturated fatty acids (SFA), docosahexaenoic acid (C22:4; DHA), and odd-chain fatty acids (OCFA), such as C15:0-antiso and C19:1-cis 10, increased significantly (P < 0.05) with the increasing age and body weight of the ewes, while the ALA and unsaturated fatty acids (UFA) significantly decreased (P < 0.05). The principal component analysis (PCA) revealed a positive association between the age and the OCFA, ALA and small-chain fatty acids (C6:0 and C8:0). In addition, the type of birth showed a positive association with the fat, lactose and palmitoleic acid C16:1 cis9. Conversely, there is a negative association between the UFA, monounsaturated fatty acids (MUFA) and PUFA. In addition, the body weight (BW) and litter size were negatively associated with the protein, SFA and medium-chain fatty acids (C10:0, C12:0, C14:0 and C16:0). The physiological factors generally suggested that the milk quality and essential FA, such as ALA, were influenced by the type of the lamb’s birth and the age of the ewes.