Most feeding systems recognize that intestinal digestibility of rumen undegradable protein varies among feeds and different samples of the same feed (mainly in heat processed feeds). In spite of the evidence that intestinal digestibility of individual AA varies within feed, the difficulty in its determination results in the assumption that digestibility of each individual AA is constant and equal to the digestibility of total protein. Measuring intestinal digestion of proteins and AA in vivo is difficult, expensive and time consuming. Therefore, alternative methods have been developed for routine analysis of intestinal digestibility of protein and AA. The mobile bag technique was developed to estimate intestinal digestion of protein and AA in ruminants. While it has proven useful in identifying differences in intestinal digestibility of protein and AA between and within feeds, the collection of bags in the feces should be challenged, and a full independent validation against in vivo models is needed. A modified three-step in vitro procedure has been recently proposed and validated against an in vivo animal model to be used in the determination of intestinal digestion of protein and AA in ruminants. While results on few samples are promising, validation with a larger set of samples is required. The availability of an easy, cheap and reliable method to determine intestinal digestion of protein and AA in ruminants may help in improving diet formulation and the efficiency of N utilization in ruminants.
|Journal||EAAP Scientific Series|
|Publication status||Published - 1 Dec 2010|