EFFECTS ON UREA CONCENTRATIONS IN BLOOD OF SWINE

Normal urea concentrations in the blood of clinically intact pigs are between 4 mmol/l serum and 7 mmol/l serum, with 90 per cent of the urea originating from deaminated amino acids and some ten per cent from microbial digestive processes via NH3. Urea concentrations in the blood can be influenced by many factors. Piglet experiments have shown concentrations to be reduced by twelve to 18 per cent by addition of 0.5 to 1.5 per cent formic or fumaric acid. Improved initiation of proteolysis has been discussed as a causative factor, as pepsin can come to stronger effectiveness due to lower gastric pH, when applied just after feeding. Gastric fermentations were reduced in parallel with significance by an order between 50 and 60 per cent, while feed uptake was increased by nine per cent and body weight by eleven to 13 per cent. Wheat bran and alfalfa meal were conducive to lowering urea concentrations by two per cent relative to every one per cent of crude fibre increase, provided that crude protein levels in the ration accounted for 13 or 18 per cent. No crude fibre effect at all was recordable, when the crude protein level amounted to 24 per cent. The modes of action of the two dietary factors are separately attributed to the diurnal course of gastric digestion (acids) and to colonic digestion (crude fibre).