Effect of Reduced Crude Protein Level on Fecal Nitrogen Excretion and Blood Profile in Finishing Pigs

The purpose of this experiment was to evaluate the effects of a low-protein diet on the selected variables of protein and energy metabolism in the blood serum as well as on the indicators of fermentation in the faeces (fecal crude protein, ammonia, pH, volatile fatty acids, and dry matter). Twelve finishing pigs (initial body weight: 64.6 ±  3.35 kg) were randomly divided into two groups and fed basal diets with crude protein (CP) levels of 13.6% and 15.4%, respectively. The Lysine, Methionine, Threonine, and Tryptophan levels in the 13.6% CP group were the same as those in the 15.4% CP group after the addition of four crystalline amino acids—Lysine, Methionine, Threonine, and Tryptophan to the diet. The blood and faeces samples were taken from the cranial vena cava and from the rectum at the end of the study period (44 days). The results showed that with the decrease in dietary CP level from 15.4% to 13.6% (a decrease of 1.8%), the fecal crude protein, the fecal ammonia, as well as the blood urea level decreased in the experimental group compared to the control group (P< 0.05 and 0.01, respectively).