Effect of the feeding system (grazing vs. zero grazing) on the production, composition, and fatty acid profile in milk of creole goats in northern Mexico

Abstract

The objective was to compare the productive performance, composition, and fatty acid profile of the milk of creole goats under a grazing
system or in zero grazing. Fourteen creole adult goats were used, randomly distributed in two homogeneous treatments (grazing, n = 7;
zero grazing, n = 7). The goats had an adaptation period of 14 d, and a 49 d experimental period. Milk production and its chemical
composition were analyzed in a repeated measures design. The fatty acid profile of the milk, the chemical composition of the feed, and of
the plants consumed by the goats were analyzed by analysis of variance.They were manually milked once a day between 0600 to 0700 h
daily. Milk production was measured individually with a portable scale. The quality (protein, fat, and lactose) was measured through infrared
spectrophotometry and the fatty acid (FA) profile was obtained through gas chromatography. Differences were found (p<0.05) between
the treatments for production, fat, protein, and lactose yield. The main milk FAs in both systems were C6:0, C14:0, C18:1n-9, C16:0
and C18: 0. A higher content of saturated FAs was found in the milk of the zero grazing (p<0.05) and a higher content of unsaturated
FAs in the milk of grazing goats (p<0.05). The milk fat of grazing goats had 43% higher concentration of the 9-cis, 11-trans isomer of
conjugated linoleic acid compared to milk fat from zero grazing goats. The milk of grazing goats is concluded to have a more attractive
lipid profile for the consumer, with a higher concentration of compounds with potential beneficial effects on human health