Changes in fatty acid profile and iodine content in milk as influenced by the inclusion of extruded rapeseed cake in the diet of dairy cows

The aim of the study was to evaluate the effect of extruded rapeseed cake in diets of dairy cows on changes in milk fatty acid profile and iodine content and on the thyroid gland status. Four Holstein cows were divided into 2 groups _ experimental (R) fed a diet based on extruded rapeseed cake and control (S) fed a diet based on extruded full-fat soya. The experiment was divided into 4 periods of 42 days (21 days of preliminary period and 21 days of experimental period). Samples of milk and blood were taken three times a week during the experimental period. DMI was not affected by the treatment. Milk yield and 4% FCM were lower in R than in S (P less than 0.05). Percentages of milk fat and protein were higher in R than in S (P less than 0.05). The total concentration of SFA and UFA was not affected by the treatment. However, the concentration of MUFA in R was higher (34.71 g/100 g) and the concentration of PUFA was lower (4.00 g/100 g) than in S (32.14 and 5.54 g/100 g, respectively (P less than 0.05). The concentrations of C18:2 and C18:3 isomers and metabolites in R were lower than in S (P less than 0.05). The concentrations of cis-9, trans-11 CLA and trans-10, cis-12 CLA was lower in R (0.71 and 0.016 g/100 g) compared to S (0.97 and 0.022 g/100 g, respectively, P less than 0.05). The index of atherogenicity and peroxidisability was lower in R than in S (P less than 0.05). The index of desaturation was not affected. The mean daily intake of glucosinolates (Gls) in R was 50.14 mmol and resulted in a significant decrease in iodine concentration in milk in R in comparison with S resulting in the lower daily iodine output in milk in R compared to S. Concentrations of T3 and T4 in blood plasma were not affected by the treatment.