Summer diet selection of dairy goats grazing in a Mediterranean shrubland and the quality of secreted fat

This study aims to evaluate the preferences and nutritive value of dairy goats summer diet selection in a Mediterranean shrubland and its effect on milk yield and quality, with specific reference to fatty acid (FA) composition. A commercial flock of the indigenous Payoya goat was used in the present study, carried out from August to October of 2008. The goats were divided into two groups: a free-range grazing group (goats had free access to pasture, (G) n = 100) and an indoor group (goats were housed in a stable, and received 1.5-2 kg/goat/day of alfalfa hay and pea straw mixture, (I) n = 60). A supplementary concentrate was fed to both groups at 0.5 kg/goat/d, during milking. Diet composition of the grazing goats was estimated through in situ observations. Chemical composition and nutritive value of selected diets, hay and concentrate samples were analyzed. Milk samples were taken from pooled milk of all animals in each group the day after diet observations, and basic chemical composition and FA profile were performed. Myrtus communis and Pistacia lentiscus were the most frequently ingested species. Milk yield and basic chemical composition were greater in group I than in group G for most of the studied parameters. The percentages of the nutritionally desirable FA (α-linolenic acid, C20:5 n-3, total n-3 PUFA) were significantly higher in milk from the G group, while the C18:2 n-6 cis, total n-6 PUFA and n6:n3 ratio were significantly lower than in I group. Total conjugate linoleic acid and its isomers were not affected by feeding-type group. In conclusion, the pastures selected could be considered to be of low to intermediate nutritional quality (4 MJ/kg DM of net energy for lactation). In addition, small but significant differences were found on milk yield and milk FA composition according to feeding treatment (grazing vs. concentrate-forage diet). Particularly, grazing goats showed higher levels of FA recognized as having beneficial effects on human health.