Resumen:
Rumen fluid disposal from slaughterhouses represents a major environmental challenge due to the
presence of high levels of ammonia and phosphorus. The loading of these limiting nutrients into the soil
and aquatic systems triggers eutrophication. Fortunately, the fluid is also rich in fibrolytic and other
enzymes that could, alternatively, be used to enhance feed utilization in animals. Therefore, the aim of
this study was to evaluate rumen fluid as a potential source of exogenous feed enzymes using a variety of
test substrates. Hydrolytic enzyme activities of carboxymethyl cellulase, a-amylase and microcrystalline
cellulase (avicellase) were measured in the rumen fluid to determine its enzymatic capabilities.
Centrifuged and sonicated rumen fluid was used to pre-treat milled corn grain, barley grain, soybean
meal, common vetch grain, bitter vetch grain, chickling vetch grain, alfalfa hay and common vetch straw
substrates at 0, 1, 2, 3, or 4 mL per 100 g dry matter. Rumen fluid-treated substrates were subjected to a
water solubility test and in vitro ruminal fermentation. The activities of carboxymethyl cellulase, avicellase
and amylase were observed to be 377.8, 333.4 and 282 U/mL, respectively. Water solubility of dry
matter in bitter vetch grain, chickling vetch grain, common vetch grain and soybean meal increased
linearly with level of rumen fluid treatment. The highest solubility was observed in substrates treated
with 4 mL rumen fluid per 100 g dry matter (P < 0.05). With the exception of common vetch grain, other
feeds had the highest (P < 0.05) biogas production at 24 and 48 h when pre-treated with 3 and 4 mL
rumen fluid per 100 g dry matter. Pre-treatment of feeds with rumen fluid significantly (P < 0.05)
improved total fermentable fraction of corn grain, bitter vetch grain, chickling vetch grain, alfalfa hay and
common vetch straw. However, digestible organic matter and metabolizable energy of common vetch
grain were not influenced by rumen fluid pre-treatment. These results showed that rumen fluid has the
potential to be used as an environmentally friendly source of exogenous feed enzymes that enhance feed
utilization in ruminants.