EFFECTS OF FEEDING A HIGH LEVEL OF TOWER RAPESEED MEAL IN DAIRY RATIONS ON FEED INTAKE AND MILK PRODUCTION

In experiment 1, 12 cows were used to compare the two (0–0) rapeseed meal (1788 and Tower) varieties with the commercial rapeseed meal (CRSM) and soybean meal (SBM). Feed intake, milk yield and fat content were not different (P > 0.05) among the four treatments; however, protein content was higher (P < 0.05) for the cows fed CRSM and SBM diets than for those fed the 1788–RSM diet. But more (P < 0.05) milk fat was produced by the cows fed 1788–RSM than by those fed CRSM and SBM diets. In experiment 2, eight cows were used to determine the effects of replacing SBM with Tower and also replacing a portion of Tower with urea (TU) in a mixed or extruded (TUE) form on feed intake, milk yield and nitrogen (N) retention. No differences were observed in feed consumption, milk yield or composition among the treatments. Serum thyroxine (T 4 ) level was higher (P < 0.05) for the cows fed SBM than for those fed the 1788–SBM and was similar to levels for cows fed CRSM and Tower in the first experiment. However, no differences were found in thyroxine level in the second experiment. Extrusion of Tower–urea mixture increased (P < 0.05) the N retention compared with other treatments. These short-term studies suggest that up to 25% Tower RSM can be used in dairy rations without adverse effect on performance.