Effects of full-time v . part-time grazing on seasonal changes in milk coagulation properties and fatty acid composition

For this research communication our objective was to investigate to what extent milk coagu-lation properties and milk fatty acid (FA) composition were affected by different feeding sys-tems, season and their interaction. Eighteen cows in total were subjected to one of threedifferent feeding system treatments: full-time grazing or part-time grazing combined withindoor feeding of fresh grass with low or high concentrate supplementation. Milk was sampledin spring, summer and autumn. Milk coagulation time was 15.0, 19.0 and 17.7 min, coagula-tion dynamics 1.67, 3.41 and 1.79 min, and curd firmness 52.7, 32.4 and 47.0 mm in spring,summer and autumn, respectively. Thus, milk coagulation properties of the milk were lowerduring summer. There were strong seasonal effects on milk FA proportions, but there were notalways changes with progressing season, or changes were different with respect to the impactof the feeding systems (system × season interaction). The milk fat was favourably rich in oleicacid, conjugated linoleic acid andα-linolenic acid and had a lown-6/n-3 fatty acid ratio in allsystems. Factors like seasonal variations in grass composition and the energy balance of thecows were considered relevant for the milk FA composition. Overall, seasonal variations inmilk quality were less pronounced with part-time grazing with fresh grass indoors as com-pared to full-time grazing without concentrate.