Methionine requirement of weanling Large White x Landrace pigs and determined by plasma urea concentration, nitrogen retention and some urinary nitrogenous components.

The methionine requirements of weanling Large White x Landrace pigs fed a 20% protein cassava flour-soybean meal diet were evaluated using nitrogen balance, plasma urea concentration, urinary nitrogenous end products and the index--(allantoin/urinary urea) x protein intake (A/U x Ip). Sensitivities of the response criteria to sex differences in methionine requirements were compared. Allantoin excretion consistently and significantly (P less than 0.05) increased with increasing methionine levels to a maximum of 0.55% total methionine. Maximum nitrogen retention was observed in diets containing 0.55, 0.47 and 0.55% total methionine for castrated males, females and the pooled data for both sexes, respectively. Minimum urea concentration in plasma was obtained with the diets containing 0.55% methionine. The index, + A/U x Ip, showed that the diet was better utilized when it contained 0.63, 0.55 and 0.63% total methionine in castrates, females and combination of the two sexes, respectively.