STUDIES ON THE USE OF PROTECTED SOYBEAN-MEAL IN RATIONS FOR LACTATING COWS

Three experiments with lactating Friesian cows were conducted. The concentrates (KF) which were fed contained 12 % or 9 % unprotected soyabean meal (KFA or KFC) or 9 % SoyPass (KFB). The corresponding crude protein contents amounted to 15.4 %, 11.8 % or 11.2%. A grass silage with 18.9% crude protein in the dry matter was given as roughage. The reduction in protein degradability of soyabean meal, which was determined by the nylon bag technique amounted to 15.3 % U for SoyPass as compared to untreated soyabean meal and to 7.9 % U or 6.6 % U for KF B as compared to KFA or KFC. N-excretion with faeces and milk, as studied in N-balance trials with fistulated cows, were not affected by ration type. But N-excretion with urine was significantly reduced by 32 % or 26 % respectively, when KFB or KFC was fed instead of KFA. Feeding KFA showed also a significantly increased urea content in the milk and a tendency towards a higher N-retention. Iso fatty acids contents and NH3-concentration in the rumen fluid were higher in group A than in the groups B and C. The other rumen parameters did not show any differences. Concerning performance data no significant differences between groups could be detected. The effects as found in the experiments were only due to the protein contents in the concentrates and not to the degradability of the soybean protein.