Date Full Report Received06/02/2003
Date Abstract Report Received06/02/2003
InvestigationInstitution: Michigan State University
Primary Investigator: Nathalie L. Trottier
Co-Investigators: Gyles Randall
Funded ByNational Pork Board
Reducing dietary crude protein concentration leads to a significant reduction in nitrogen losses in the urine, in turn reducing ammonium concentration and ammonia emission. Amino acids, the building blocks of protein, can be supplemented in crystalline form in diets where crude protein concentration is decreased, to make-up for deficiencies in essential amino acids. Amino acids in crystalline form have the advantage over those found bound in protein, in that they do not require digestion, and are rapidly absorbed intact. Previous research has shown that dietary crude protein can be reduced when amino acids in crystalline form are added in diets fed to growing pigs. However, the extent to which crystalline amino acids can be supplemented in place of protein-bound form is limited as growth performance of the pig and its ability to retain protein is compromised when the reduction in dietary crude protein exceeds 4 to 5%. Our study was designed at addressing whether the ability of the pig to retain protein when fed such diets is related a decrease in the integrity of gut cell morphology and activity. The gut possesses the highest rate of protein turnover (i.e., synthesis and degradation) of all organs in the body, and it now recognized as being an active “scavenger” of amino acids. Thus, the gut not only serves the important function of providing nutrients to the rest of the body, but also requires nutrients and amino acids to develop normally. We hypothesized that amino acids bound to protein may be preferentially utilized by the gut compared to amino acid in crystalline form. The results of our study demonstrate that the height and width of intestinal cells was reduced, which could impact the absorption of amino acids themselves and other nutrients. Our study also found that gut cells synthetic activity decreased, suggesting that reducing dietary crude protein may decrease gut functions. However, this translated into a decrease in growth performances in pigs fed 6 to 9% lower protein as intact protein source (corn and soybean meal). In pigs fed 3 to 6% lower protein, growth performance was not affected, despite some changes in intestinal cell morphology and synthetic activity. Thus, it is recommended that diets containing at least 3% less protein as intact protein with supplemental crystalline amino acids be fed to growing pigs.