Effects of pelleting and expanding of vegetable feeds on in situ protein and starch digestion in dairy cows

Abstract

In situ digestion of protein and starch in barley, oats, wheat, wheat bran, maize, sorghum, peas, and soyabeans was evaluated in dairy cows after milling (untreated), pelleting (ca. 81°C) and expander processing at two different temperatures (110 or 130°C). Effective degradation of crude protein (EPD) and starch (ESD) in the rumen, as well as total tract indigested protein (IP) and starch (IS) fractions, were determined by in situ methods. Pelleting significantly decreased EPD of wheat and wheat bran by 14 and 10 percentage units, respectively, and increased ESD in maize by 10 percentage units. Expander treatment efficiently protected protein from rumen degradation in all feeds evaluated, except maize. The ESD of maize, sorghum, peas and oats increased with 31, 18, 22 and 5 percentage units, respectively, after expander treatment at 130°C. The IP fraction of sorghum and peas increased after expander treatment. In maize, sorghum and peas the IS fraction decreased by heat treatment. It is concluded that protein and starch digestion of vegetable feeds in dairy cows can be modified by different heat treatment.