Nutritive Value of Feed Evaluated by Net Flux of Nutrient in Portal-Drained Viscera

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The objective of this study was to evaluate the nutritive value of feed with net flux of nutrient by portal-drained viscera in ruminants. Five calves implanted catheters into the portal vein, the messenteric vein and the artery was used, and two of them had the duodenal cannula. They were fed seven diets: a basal diet (10% CP) consisted of 30%. hay and 70%, concentrate, and others were supplemented fish meal (FM) or soybean meal (SBM) at three levels, isonitrogenously. The calves (BW : 83 to 281 kg) were given the maintenance requirement of energy every 12 h. The samples of duodenal contents and bloods were taken 6 times and 12 times daily, respectively. As an indicator, chromic oxide was used for the duodenal flow, and p-aminohippurate was for blood flow. The obtained results by regression analysis were as follows. 1. α-amino nitrogen (AAN) release by PDV for all diets averaged 35.1% of nonammonia N entered the duodenum. 2. Ammonia N release by PDV of N intake was 34.8% for FM and 29.9% for SBM, and urea N uptake was 18.2% and 7.5%, respectively. 3. AAN release in response to the dietary N content conformed to quadratic regression (R2=0.99), and the peak value for FM compared with SBM was greater at a higher dietary N content. 4. Glucose absorption tended to be greater for SBM than for FM. These new knowledge imply that the usual concept on ruminant protein nutrition must be changed, and that the evaluation for feed nutritive values based on net nutrient flux by PDV is probably more reliable than on the digestion.