Abstract
: A series of in vitro and in vivo experiments were conducted to investigate the effects of the mixture of Tween 80 and cellulolytic enzymes (xylanase and cellulase) on total tract nutrient digestibility and rumen cellulolytic bacterial adhesion rates in Holstein steers. Ground timothy hay sprayed with various levels of Tween 80 and cellulolytic enzymes was used as substrates in an in vitro experiment to find out the best combinations for DM degradation. The application level of 2.5% (v/w) Tween 80 and the combination of 5 U xylanase and 2.5 U cellulase per gram of ground timothy hay (DM basis) resulted in the highest in vitro dry matter degradation rate (p<0.05). Feeding the same timothy hay to Holstein steers also improved in vivo nutrient (DM, CP, CF, NDF and ADF) digesibilities compared to non-treated hay (p<0.05). Moreover, Tween 80 and enzyme combination treatment increased total ruminal VFA and concentrations of propionic acid and isovaleric acid with decreased acetate to propionate ratio (p<0.001). However, adhesion rates of Fibrobacter succinogenes and Ruminococcus flavefaciens determined by Real Time PCR were not influenced by the treatment while that of Ruminococcus albus was decreased (p<0.05). The present results indicate that a mixture of Tween 80 and cellulolytic enzymes can improve rumen environment and feed digestibility with variable influence on cellulolytic bacterial adhesion on feed.
Highlights
Non ionic surfactant, Tween 80, has been used as a feed additive to improve rumen environment and animal productivity
Previous studies indicate that Tween 80 may provide some positive effects on exo- and endogenous enzyme activity of rumen bacteria, total bacterial growth
Responses by ruminant animals to exogenous enzymes have been variable in the literature
Summary
Tween 80, has been used as a feed additive to improve rumen environment and animal productivity. Beauchemin and Rode (1996) suggested that exogenous enzymes could enhance fibrolytic enzyme activity by less than 15%, and DM disappearance and bacterial colonization of lucerne hay treated with exogenous enzymes prior to feeding (Yang et al, 1999). Wang et al (2001) reported that addition of exogenous enzymes improved bacterial adhesion rates to feed particles. Hristov et al (1998b) suggested that when enzymes were treated to feed or administrated into the abomasum, intestinal viscosity was reduced, which resulted in 1.2-1.5% increase in total tract DM digestibility. There have been some attempts to determine effects of the mixtures of Tween 80 and cellulolytic enzymes on ruminal fermentation and feed digestion with inconsistent results. Baah et al (2005) suggested that the mixture of Tween 80 and cellulolytic enzymes increased propionate production, slowly disappearing fraction of orchardgrass and degradation rate of barley grain. Present study was conducted to investigate effects of combinations of Tween 80 and cellulolytic enzymes on nutrient digestion and to see if the combination has any effects on cellulolytic bacterial adhesion
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