The effect of heat on amino acids for growing pigs. 4. Nitrogen balance and urine, serum and plasma composition of growing pigs fed on raw or heat-treated field peas (Pisum sativum).

Experiments were conducted to determine the effect of heating field peas (Pisum sativum) on the N balance and urine, serum and plasma composition of growing pigs. In the first experiment, four diets containing raw field peas (cv. Wirrega) or field peas heated to 150 degrees (cv. Wirrega), 165 degrees (cv. Wirrega) or 150 degrees (cv. Dundale) for 15 min respectively were formulated to contain 1.15 g ileal digestible N/MJ digestible energy (DE) and 0.36 g ileal digestible lysine/MJ DE in a sugar-based diet. Digestibility estimates were based on those for the Dundale cultivar of field peas used in previous experiments. Total urine and faeces collection from eight pigs was conducted over two 7 d collection periods with a 7 d diet change-over period. Serial blood sampling from the external jugular vein was conducted on the final day of each collection period. There was no significant difference (P > 0.05) in the N balance or apparent biological value of the field-pea treatments. Pigs fed on diets containing peas heated to 150 degrees (cv. Wirrega) or 165 degrees (cv. Wirrega) had a significantly lower (P < 0.01) daily output of urea and uric acid in the urine, and depressed serum protein and serum urea concentrations. Plasma lysine concentration and daily urine lysine output were not significantly different (P > 0.05) in pigs fed on heated peas. Protein excretion in the urine of pigs fed on diets containing peas heated to 165 degrees increased 3-7 times (depending on estimation technique) the level observed in pigs fed on diets containing raw peas. A second experiment was conducted to determine the apparent ileal digestibility of N and amino acids in cv. Wirrega field peas. This study revealed that N digestibility (0.44) and lysine digestibility (0.35) in peas heated to 165 degrees were significantly lower than the cv. Dundale estimates (0.57 and 0.62 respectively) used in diet formulations. The depressed serum and urine variables in pigs fed on heated peas were attributed to overestimation of digestibility. The results exemplify the fact that it is not possible to draw general conclusions as to the effects of heat on any particular protein concentrate. Variability in N balance experiments and problems associated with urine analysis are suggested as likely reasons for the current study not reflecting poor utilization of ileal digestible lysine from heat-treated field peas.(ABSTRACT TRUNCATED AT 400 WORDS)