EFFECTS OF TREATING RAPESEED MEAL AND CASEIN WITH FORMALDEHYDE ON THE FLOW OF NUTRIENTS THROUGH THE GASTROINTESTINAL TRACT OF FISTULATED HOLSTEIN STEERS
Four Holstein steers fitted with T-type soft plastic cannulae in the rumen, abomasum and terminal ileum were fed four semipurified pelleted diets containing 19% rapeseed meal (RSM) or 7.5% casein, both untreated or treated with formaldehyde (FA), during the four experimental periods. The diets were fed from an automatic belt feeder device. FA treatment of casein increased (P < 0.01) the flow of total N and non-ammonia-N (NAN) as a percentage of intake through the abomasum of steers. Significantly more (P < 0.05) bacterial N passed through the abomasum of steers fed RSM diets than those receiving the casein diets. FA treatment caused a nonsignificant (P > 0.05) depression in the apparent digestibility of dry matter (DM) in the small intestine of steers receiving the treated diets. Significantly greater (P < 0.05) quantities of total N and NAN passed through the terminal ileum of steers consuming the RSM diets compared to those fed casein diets. Total determined amino acids in the abomasum as a percentage of amino acid intake were lower (P < 0.01) for untreated casein diet compared to the other three treatments. FA treatment increased (P < 0.05) the flow of lysine, histidine, valine, isoleucine, leucine and tyrosine in the abomasum of steers receiving FA casein compared with untreated casein, but had no effect in the case of treated RSM. FA treatment increased the absorption of most of the essential amino acids in the small intestine of steers receiving the FA casein compared to casein diet. Treatment of RSM resulted in reduced (P < 0.05) fecal excretion of threonine, valine, isoleucine, leucine, phenylalanine and tyrosine.