the digestibility of sugarcane tops silage by rumen bacteria or microorganisms of holstein cows and buffaloes of khuzestan

introduction: sugarcane (saccharum officinarum) is widely cultivated in south west of iran for production of sugar. after harvest, a lot of sugarcane tops remain on the farm that can be used to feed ruminants. the total digestible nutrients (tdn) and crude fiber of sugarcane top is about 72% and 39%, respectively. the digestibility of dry matter (54%) and crude protein (39%) of sugarcane top is low. large amount of sugarcane top is wasted or burned annually. the sugarcane tops is important as forage for feeding of livestock. preparation of sugarcane tops silage is a useful method to store and using it in whole seasons, prevent from wasting at the harvesting season and rich it using additives. due to the low fermentable carbohydrate, and fibrous nature of sugarcane top, its durability of silage is short and quality of silage is inappropriate. therefore, different methods can be used to enrich and enhance durability. the digestible protein of sugarcane top is low, so a proper nitrogen source is useful to improve the nutritional value of the sugarcane top. using urea and molasses individually, is not suitable method for long term storage of sugarcane tops silage. the acids prevents from degradation of proteins in the silage, and decrease the ph rapidly. the bacteria have the most important role in digestion and degradation of starch, protein and plant cell wall. the aim of present experiment was to study the effect of sulfuric acid added to sugarcane top silage on digestion activity of rumen bacteria and whole rumen microorganisms, and followed by to compare the digestibility of sugarcane silage treated with urea + molasses and sulfuric acid between holstein cattle and khuzestan water buffalos. materials and methods: the experimental treatments were ensiled sugarcane top by some additives included: 1) untreated (no additive) 2) urea (1%) + molasses (3%), 3) sulfuric acid (2.4% dry matter weight), 4) both, urea+molasses and sulfuric acid. rumen fluid was taken from buffalo and holstein cow through rumen fistula. results and discussion: the in vitro digestibility of dry matter (dm) of sugarcane top silage by total rumen microorganisms of cow was more than buffalo. regardless of the type of animal, digestibility of dm by whole rumen microorganisms for urea+molassses and acid, and digestibility neutral detergent fiber for acid was highest amount (p<0.05). by using two-stage digestion method and specific rumen bacteria culture medium method, digestibility of dm and neutral detergent fiber (ndf) was highest in treatment containing 2.4% acid sulfuric. the digestibility of dm by buffalo rumen bacteria was more than cow. regardless of the type of animal in specific rumen bacteria culture medium, digestibility of dm and ndf by rumen bacteria for acid treatment was highest amount (p<0.05). therefore acid had no negative effect on microorganisms, particularly bacteria. even possibly because of sulfur in acid had a positive effect on growth of microorganisms and follow that digestibility of the nutrients. therefore, sulfuric acid may be used for sugarcane top silage making. conclusion: the results of present experiment shown that using sulfuric acid not only had a negative effect on microorganisms, particularly bacteria, but also probably due to the presence of sulfur in its structure, had positive effect on their growing and thereupon digestion of nutrients. according to the results of this research, the digestibility of nutrients by whole rumen microorganisms of holstein cow was more than river buffalo of khuzestan. while, digestibility of nutrients by bacteria in the two-stage digestion and specific rumen bacteria culture medium methods, in buffalo was more than cattle. in general, in this study regardless of the type of animal, digestibility of dm ndf, in treatment containing sulfuric acid was more than other treatments. probably at this level of sulfuric acid (2.4%), there was no decrease in the number of bacteria, or using 2.4% of commercial sulfuric acid had no negative effect on the bacteria or whole rumen microorganisms. therefore, sulfuric acid can be exploited in the making of sugarcane silage.