Wpływ grupy rasowej kóz i sezonu żywienia na właściwości fizykochemiczne tłuszczu mleka

Abstract

The aim of the study was to evaluate the effect of goat breed and the feeding season combined with the lactation stage on basic chemical composition, fat dispersion, fatty acid profile and cholesterol content in milk. The subject of the study included 480 milk samples collected from two groups of goats, i.e. improved with a known origin on the father’s side (203) and various crossbreeds of unknown origin – breedless (277), in three production seasons (lactation stages): winter (beginning of lactation) – 166, spring-summer (middle of lactation) – 161 and autumn (end of lactation) – 153. The following parameters were determined in milk samples: basic chemical composition (content of protein, fat, lactose and dry matter), fat dispersion, fatty acid profile and cholesterol content. It was shown that despite a lower daily milk yield, crossbreeds of goats of unknown origin produced milk both with favourable chemical composition, significantly higher fat dispersion and higher cholesterol content compared to the improved crossbreeds. The highest concentration of dry matter components, including fat and protein, was characteristic of milk collected in the autumn feeding period, at the same time with the lowest daily milk yield. Along with the course of lactation the dispersion state of fat was increasing and so was the concentration of cholesterol. The breed group of goats had an impact on milk fatty acid profile. A significantly lower concentration of saturated fatty acids and higher mono- and polyunsaturated fatty acids was found in the milk of goats of unknown origin, and that was generally observed in each season of production. Improved goats produced milk with a significantly higher concentration of odd-chain fatty acids and branched-chain fatty acids. A higher concentration of beneficial fatty acids, including CLA, was found in milk in the spring-summer season (lactation stage II), i.e. when goats were grazing fresh green pasture.