Nitrogen transactions in the rumen of sheep given a barley straw diet supplemented with untreated or formaldehyde-treated sunflower seed meal

Abstract

The effect of formaldehyde treatment of the sunflower seed meal in a barley straw based diet on rumen N transactions was studied in two fistulated crossbred sheep using 15N-ammonia and 15N- and 14C-urea. Treatment decreased organic matter and N digestibility to a small extent, but substantially decreased urine N excretion so that N retention increased. Treatment resulted in decreases in ammonia and urea synthesis which were reflected in reduced rumen ammonia and plasma urea levels; the net flow of N from the rumen ammonia pool to the plasma urea pool was reduced by 50%. 56-65% of the bacterial N was derived from ammonia. The contribution of bacterial N to N in the protozoal fraction decrease..