Effects of Polyethylene Glycol (PEG) on In Vitro Dry Matter and Nitrogen Digestibility of Leucaena Species and Signal Grass (Brachiaria decumbens)

Abstract

The tropical legume Leucaena contains condensed tannin (CT) that binds protein and other components of feed. In fact, Leucaena reduces digestibility of nutrients and depending on tannin content and astringency. Polyethylene glycol (PEG) has ability to neutralize CT by displacing proteintannin complexes, as a consequence of CTs interact more strongly with PEG than they do with protein. In vitro studies were conducted to investigate the effect of polyethylene glycol (PEG) on in vitro digestibility of Leucaena species and grass. In vitro studies were conducted in two stages as described by Tilley and Terry (1963) and Jones et al. (1998).The results indicated that the digestibility vary depending on the nutrients content of forages and its CT content. Low tannin content of forages had a high digestibility of dry matter and nitrogen, and the rate of ammonia-N production. PEG consistently improved the digestibility of nitrogen and to some extent of dry matter, and the rate of ammonia-N production of tannin-containing forages but not non-tannin-containing of grass. The maximum values were 60.6%, 71.2% and 93.6 mg/d for corrected dry matter digestibility, nitrogen digestibility and the rate of ammonia-N production respectively, when PEG was included at rate of 200 mg/g samples of forages. High tannin content of forages required more PEG to neutralize the effect of tannin to the same extent of low tannin content forages. PEG, on the other hand, had no effect on digestibility and the rate of ammonia-N production on non tannin-containing grass.