Changes in the composition and fatty acid profile of Najdi ewes’ milk before and after weaning

Abstract

This trial aimed to study the changes in the yield, composition, and fatty acid (FA) profile of ewes' milk during suckling and milking periods. Nineteen multiparous Najdi ewes were kept under identical management and feeding conditions during a 12-week trial that was divided into two periods. Milk samples were collected on each sampling day from the total yield during the suckling (3rd, 6th, and 9th week) and milking (12th week) periods. The milk yield and the total solids, fat, protein, and lactose contents of the milk remained constant throughout the suckling weeks, but the protein content increased and milk yield and lactose content decreased after weaning. There were no differences in milk saturated FA (SFA), unsaturated FA (UFA), and monounsaturated FA (MUFA) contents during the suckling and milking periods, whereas the polyunsaturated FA content increased during the milking period. There were no differences in the individual milk SFA during the weeks of suckling, but the contents of caproic acid (C6:0), caprylic acid (C8:0), margaric acid (C17:0), and stearic acid (C18:0) decreased. However, myristic acid (C14:0), lauric acid (C12:0), and isomers of pentadecanoic (C15:0) acid increased during the milking period. The percentage of vaccenic acid (C18:111t), rumenic acid (C18:29c,11t; conjugated linoleic acid (CLA)), ω-3 FA group, and the atherogenicity index did not differ during the suckling period, but increased after weaning in the 12th week of lactation. This study demonstrated that weaning lambs in Najdi ewes is probably a factor that strongly affects milk traits by changing yield, composition, and FA profile.

Identification of Genetic Polymorphisms of PI, PIII, and Exon 53 in the Acetyl-CoA Carboxylase-α (ACACα) Gene and Their Association with Milk Composition Traits of Najdi Sheep

“…The composition of the milk (fat, protein, and lactose) was analyzed 24 h after collection using a Milko-Scan FT6000 (Foss, Hillerød, Denmark), and the milk was then stored at −20 °C until the analysis of the FA profiles. The extracted lipids were obtained from 30 mL milk samples according to Luna, et al [ 14 ], and FA methyl esters (FAMEs) were prepared according to [ 15 , 16 ]. The relative proportions of each FA profile were calculated based on the ratio of the peak area of one FA to the total peak area of all FAs in the fat sample.…”

Postpartum Body Condition Score (BCS) and Lactation Stage (30 and 60 Days) Affecting Essential Fatty Acids (EFA) and Milk Quality of Najdi Sheep

“…The fat extraction from 20 mL of the milk sample was stored at 20 °C until FA profiles analysis, according to Luna et al [ 14 ]. FA methyl esters (FAMEs) were prepared, according to [ 15 , 16 ] and using Hexan. Mass spectrometry data were acquired and processed using the GC-MS Chem-Station data system.…”