Whole tract and post ruminal digestibility determined by in situ ruminal, intestinal mobile nylon bag and whole tract nylon capsule methods

Whole tract and post ruminal digestibility of crude protein (CP) and dry matter (DM) in ryegrass, alfalfa hay (high and medium quality) and maize silage were determined by means of a rumen in situ nylon bag, a mobile nylon bag and a nylon capsule method as well as by calculations that combined the methods. Calculation of whole tract digestibility was from results of rumen in situ nylon bag and mobile nylon bag methods and calculation of post ruminal digestibility was from results of the nylon capsule and rumen in situ nylon bag methods. Three dry cows (Red Holstein × Black Friesian) fitted with ruminal and duodenal cannulas were used for testing the nylon bag and mobile bag methods, whereas the nylon capsule method utilised three dairy cows (Red Holstein × Black Friesian). Differences between determined and calculated values for whole tract digestibility of CP and DM ranged from −3.3 to +2.9%, and from −0.1 to −8.5%, respectively. Differences between determined and calculated values of intestinal digestibility of undegraded CP were higher and ranged from −10.6 to +13.8%, and from +0.4 to +17.5% for CP and DM, respectively.