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

Three experiments with lactating Friesian cows were conducted. The con centrates (KF) which were fed contained 12 % or 9 % unprotected soyabe an meal (KFA or KFC) or 9 % SoyPass (KFB). The corresponding crude pro tein 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 redu ction in protein degradability of soyabean meal, which was determined by the nylon bag technique amounted to 15.3 % U for SoyPass as compare d to untreated soyabean meal and to 7.9 % U or 6.6 % U for KF B as com pared 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 sho wed also a significantly increased urea content in the milk and a tend ency towards a higher N-retention. Iso fatty acids contents and NH3-co ncentration in the rumen fluid were higher in group A than in the grou ps B and C. The other rumen parameters did not show any differences. C oncerning performance data no significant differences between groups c ould be detected. The effects as found in the experiments were only du e to the protein contents in the concentrates and not to the degradabi lity of the soybean protein.