Changes in fatty acid pattern, composition and technological parameters ofmilk in dairy cows fed heat-treated rapeseed cakes in the first stage of lactation

Two groups of 8 dairy cows each (Czech Red-pied x Ayrshire x Red Holstein) were fed basal diet and concentrate mixture with either heat-treated rapese ed cakes (HRC group) or soybean meal (SBM group) within the first hundred d ays of lactation. Milk constituents (solids, fat, solids-non-fat, crude pro tein, casein, whey protein, urea, lactose, calcium, citric acid), fatty aci d pattern of milk fat, and technological traits (freezing point, acidity, h eat stability, rennetability) were determined in milk samples taken on 21st , 42nd and 100th day of lactation. Neither yield of milk and yield of any m ilk constituent, nor the content of fat, total protein, casein, whey protei n and calcium, respectively, differed (P > 0.05) between HRC and SBM groups . On the other hand, solids-non-fat and lactose content was higher (P < 0.0 5) in HRC-milk as compared to SBM-milk. Content of saturated fatty acids wa s lower (P < 0.01) and content of monounsaturated fatty acids (MUFA) and po lyunsaturated fatty acids (PUFA) higher (P < 0.01) in milk of dairy cows fe d the diet with HRC. The ratio of total C16/C18 fatty acids was by 30% lowe r (P < 0.01) in HRC-milk in comparison with SBM-milk. Content of myristic a cid increased (P < 0.01) and content of stearic acid decreased (P < 0.05) i n milk fat with increasing day of lactation irrespective of the feeding int ervention. Content of linoleic acid, total PUFAn6 and PUFA/MUFA ratio incre ased (P < 0.05) with increasing day of lactation within the HRC group. Neit her rennetability nor heat stability of milk was negatively influenced by t he presence of HRC in the diet. It was concluded that inclusion of heat-tre ated rapeseed cakes in the diet for dairy cows instead of SBM did not influ ence negatively either composition or the technological quality of milk, an d on the other hand improved its nutritive value from the viewpoint of more favourable fatty acid spectrum of milk fat.