Protein and Amino Acid Digestibility in Dairy Cows Measured with Mobile Nylon Bags Recovered in Ileum or in Faeces

Abstract

Digestibility of protein and amino acids in dairy cows was measured using the mobile nylon bag technique and collection of bags in ileum and in faeces. The feeds studied were untreated and expander treated barley and oats, solvent extracted rapeseed meal (RSM) and soybean meal (SBM), lignosulfonate treated SBM (SoyPass) and fish meal (FM). The nylon bags were recovered in ileum by trapping the bags with a magnet. The functionality of the technique was considered good although a metallic slice in the bags increased intestinal retention time. Compared to intact feed, pre-incubation 16 hours in the rumen increased digestibility of dietary protein and amino acids. The indigestible residues were in general lower in bags recovered in faeces than in ileum. In addition, some variation in digestibility among amino acids within feedstuffs seems to exist. The general conclusion was that the procedure of collecting bags in ileum can be skipped when digestibility of protein and amino acid is determined on rumen pre-incubated feed, but not when intact feed is used. Except for increased digestibility in intact barley, no major effect of expander treatment or lignosulfonate treatment on digestibility of protein and amino acids was found.