Formaldehyde treatment of concentrate diets for sheep. I. Partition of the digestion of organic matter and nitrogen between the stomach and intestines

Abstract

The effect of formaldehyde treatment of barley/soybean meal diets was studied in fistulated crossbred sheep at four protein levels. The overall digestion of organic matter was similar for all diets; the small differences in the partition of organic matter digestion in response to treatment were not significant. Dietary starch was completely digested. The partition of starch digestion was variable but was not affected by protein level or treatment. The relationship between nitrogen intake and the amount of non-ammonia nitrogen (NAN) digested in the intestines was curvilinear; NAN digested was calculated to reach a maximum when 17.4% of the dietary organic matter was crude protein. Formaldehyde treatment substantially increased the amount of NAN digested in the intestines; a treated diet in which 12.6% of the organic matter was crude protein would provide the same amount of NAN digested as the 17.4% untreated diet. The apparent digestibility of NAN in the intestines was not affected by protein level or treatment; treatment at the highest protein level appeared to cause a reduction in true digestibility to 0.75 from the mean of 0.80 obtained for the other diets. Treatment appeared to have no consistent effect on the efficiency of bacterial protein synthesis. The flows of water and of digesta from the rumen and abomasum were not affected by protein level or treatment; differences between sheep were responsible for much of the variance in these parameters. The treatment reduced rumen ammonia and volatile fatty acid levels and plasma urea levels. Neither the amount and composition of the long-chain fatty acids reaching the intestine nor their digestion there were affected by the treatment.