EFFECTS OF VOLATILE FATTY ACID TREATMENT ON THE PROTECTION OF PROTEIN IN THE RUMEN

Abstract

The increase of ammonia in rumen fluid in response to a single dose of protein supplement was used to assess microbial degradation of proteins in the rumen of sheep and cattle held without feed for about 16 h. The administration of 300 g of soybean meal and promine (50:50) pellets (9.4-mm diam) via the rumen fistula of sheep resulted in a rectilinear increase in ammonia concentration in rumen fluid over a 5-h period. The rates of increase of rumen ammonia from isonitrogenous amounts of untreated and 20% volatile fatty acid (VFA)-treated protein pellets were 9.4 and 1.5 mM/h, respectively. The decrease in the rate of protein degradation was proportional to the amount of VFA incorporated and the size of particles in the supplement. When a protein supplement containing common feed ingredients (soybean meal, herring meal and ground barley) was treated with 15% VFA and fed in meal form or as pellets to sheep and cows, the rumen ammonia was maintained for about 10 h at a lower concentration than that after feeding untreated preparations. Treatment of proteins with VFA may be useful in protecting proteins from microbial degradation in the rumen and allowing provision of supplemental protein to the lower digestive tract.