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

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Abstract
In experiment 1, 12 cows were used to compare the 2 (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 4 treatments; 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, 8 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 N retention. No differences were observed in feed consumption, milk yield or composition among the treatments. Serum thyroxine (T4) 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 1st experiment. No differences were found in thyroxine level in the 2nd 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.