Medycyna Wet. 65 (5), 310-314, 2009

full text

pdf
Joanna Barłowska, Zygmunt Litwińczuk
Genetic and environmental conditioning of milk fatty acids profile
Fat content and its composition in milk are mainly determined by the animals’ genotype and their feeding system. A similar fat content characterizes cow and goat milk; however, in buffalo and sheep milk it is almost twice as high. The fatty acids profile of cow milk is the most similar to buffalo milk. In comparison to cow milk, the fat of sheep and the goat milk contains more caproic, caprylic as well capric acid and in sheep milk also lauric, myristic and linoleic acid. The presence of linoleic acid in goat milk was not confirmed; however, a lower content of the stearic and oleic acid was noticed in sheep milk. Numerous authors indicate breed as a decisive factor in milk fat content and fatty acids profile. They claim that in milk with a higher fat content the proportion of short and medium chain fatty acids increases, and in relation to that the biggest differences in that range between Jersey (with the highest fat content) and Holstein breed (with the lowest) were demonstrated. The differences in milk fat composition between breeds are connected with metabolic processes of fatty acids synthesis, mainly with the activity of enzyme ∆9-desaturase. High positive genetic correlations among the acids with a short and medium chain, i.e. to C14:0 (r = 0.48 – 0.93) as well as a little lower between the polyunsaturated and monounsaturated acids (r = 0.11 – 0.84) were noticed. Feeding has a significant impact on milk fatty acids profile. Providing vegetable oils usually leads to the growth of an unsaturated fatty acids proportion at the cost of saturated ones. Similarly, providing fish oils as a source of C20:5 and C22:6 acids can enlarge of their share in cow and goat milk fat. It is thought that pasture feeding leads to the rise of the proportion of unsaturated fatty acids, particularly PUFA, in this CLA. It was demonstrated that the level of polyunsaturated fatty acids was higher in milk of cows pastured in mountain regions in comparison with lowland ones. It was related to the positive influence of plants from among the Compositae, Rosaceae and Plantaginaceae families, which are presented in larger quantities in the growth of natural meadows. Moreover, the year time, lactation stage, and size of fat globules has an influence on certain milk fatty acid contents.
Key words: fat of milk, fatty acids, genetic factors, environmental factors