Influence of feeding on different types of pasture on the fatty acid profile and health indices of goat milk

Abstract

The main objective of the present research was to study the change in fatty acid (FA) composition of milk fat in a Carpathian local breed during grazing on two plots characterized by a different cover with herbaceous species and woody (only herbaceous species: H and high woody species cover: W) allowances with or without concentrate supplementation (Cs: 500 g concentrate/head/d). Thus, four treatments resulted: H-U: only herbaceous species-unsupplemented, H-Cs: only herbaceous species-concentrate supplementation, W-U: high woody species-unsupplemented, W-Cs: high woody species-concentrate supplementation. Individual milk production (n = 10) was recorded daily, and milk samples were collected weekly for a seven-week period (June to August) and analysed for fat, protein, lactose, urea-N, and FAs. Milk production was not influenced by the type of pasture. The daily production of milk, 3.5% fat-corrected milk, and protein level increased and the content of fat and urea-N reduced with concentrate supplementation, whereas the content of lactose was similar. The botanical composition of pasture markedly influenced the FA profile of goat milk fat. The goats grazing in scrubland (W group) produced milk fat with higher concentrations of monounsaturated FA (C18:1 t11, vaccenic acid, VA) and polyunsaturated FA (omega 3 and conjugated linoleic acid, CLA) and lower concentrations of hypercholesterolaemic FA (HFA; C12:0 + C14:0 + C16:0). Regardless of the botanical composition of the pasture, milk fat of unsupplemented grazed goats had the lowest proportion of HFA, as well as the highest proportions of C18:1 c9, VA, RA (rumenic acid, C18:2 c9,t11), and total n-3 FA compared to the Cs groups (supplemented with concentrate). Concentrate supplementation increased short-chain FA and saturated FA content. In contrast, percentages of the nutritionally desirable FA (C18:3 c9, c12, c15; C18:2 c9, t11, C18:1 t11; C20:5n-3; C22:5n-3, and total n-3 FA) were substantially lower, whereas levels of total n-6 FA, n-6:n-3 ratio, atherogenicity index (AI), and thrombogenicity index (TI) were substantially higher in milk from Cs groups. No interactions occurred between pasture type and concentrate supplementation for milk FA composition. It is concluded that the milk from goats kept unsupplemented on the natural pasture were better in terms of nutraceutical parameters advantageous to human nutrition than the milk produced by concentrate supplementation.