Effects of low-digestible crude protein feed supplemented with amino acids on nitrogen excretion and ammonium gas generation from feces and urine of pigs

In this experiment, we examined the effects of low-digestible crude protein (DCP) feed supplemented with amino acids on nitrogen excretion from feces and urine of growing-fattening pigs during the pre-fattening period (30-70kg) and fattening period (70-110kg) and on the density of ammonium gas from feces and urine in pigs at a body weight 110 kg. Eight hogs (crossbred) were used in this study and were divided into two groups having the same mean body weight. Feed was prepared as follows ; standard feed containing DCP of 12.5% and 10.5% for the pre-fattening and fattening periods, respectively, and low-DCP feed containing DCP of 8.5% and 6.5% (a 4% reduction of DCP from the Japanese Feeding Standard for Swine) supplemented with amino acids (1ysine, methionine, tryptophan, threonine and isoleucine). The total digestible nutrient ratio was nearly the same. Feed intake, water intake, feces amount, urine volume, nitrogen and mineral contents during the test period and ammonium gas generation density from the feces and urine of 110 kg pigs were determined in this study. There was no significant difference in feed intake during the test period, but water intake was less in the low-DCP feed with amino acids group. The amount of feces showed no significant difference, but the urine volume in the low-DCP feed with amino acids group was less than that of the standard feed group as was the decrease in water intake. Although feces from both groups had similar nitrogen values, for urine nitrogen content, nitrogen intake decreased by two-thirds in the low-DCP feed with amino acids group. Mineral content excretion from feces and urine during the fattening period tended to increase in comparison with that during the pre-fattening period. The density of ammonium gas generation from feces and urine was reduced by the intake of low-DCP feed with amino acids. The peak of ammonium gas generation in the low-DCP feed with amino acids group occurred later than that in the standard feed group. These results suggest that low-DCP feed supplemented with amino acids is a valuable method for increasing the nitrogen utilization ratio and reducing nitrogen excretion, however changes in the mineral content of urine and feces must be further examined, Jpn. J Swine Science, 41, 1 : 1-10