LONG-TERM FEEDING OF RAPESEED MEAL AND FULL-FAT RAPESEED OF DOUBLE LOW CULTIVARS TO DAIRY-COWS

Long-term effects on dairy cow performances of feeding different levels of rapeseed meal and heat-treated and crushed full-fate rapeseed, both of double low cultivars, were studied. The study included the first three lactations of 85 dairy cows. Even at the highest inclusion levels of rapeseed products, 2.5 kg DM rapeseed meal plus 0.9 kg DM full-fat rapeseed per day, there were no negative effects on animal health, feed intake, feed conversion, milk production and milk composition. Compared with other protein and fat supplements, i.e. soybean meal, cotton seed meal and tallow, the milk protein content and production tended to increase (P < 0.10), while milk urea content decreased (P< 0.05). Medium (1.2-1.4 kg DM) as well as high levels of rapeseed products resulted in a significant increase in thiocyanate content but a decrease in iodine content of the milk. However, milk from the rapeseed-fed cows did not cause any metabolic disturbances when fed to rats. Milk fatty acid composition was affected by the inclusion of full-fat rapeseed, whereby the concentrations of C18:0 and C18: 1 increased and C16:0 decreased compared to when tallow was fed. Preliminary results from studies on the fertility of the cows indicated minor negative effects on primiparous cows fed the highest amounts of rapeseed products.