Effect of feeding isolates of anaerobic fungus Neocallimastix sp. CF 17 on growth rate and fibre digestion in buffalo calves

In this investigation, the effects of feeding encapsulated cells (rhizomycelia and zoospores) of a fibrolytic isolate from an anaerobic fungus (Neocallimastix sp. CF 17) on nutrient digestion, ruminal fermentation, microbial populations, enzyme profile and growth performance were evaluated in buffaloes. In three in vitro studies, the true digestibility of wheat straw was increased after addition of CF 17 to buffalo rumen fluid (p < 0.05). In Exp. 1, three groups of six buffaloes each (initial BW body weight] 148 +/- 12.0 kg) were allotted to three dosing regimes: Group 1 received 200 ml of liquid culture of Neocallimastix sp. CF 17 (about 10(6) TFU thallus-forming units]/ml); Group 2 received an encapsulated culture of the same fungi prepared from 200 ml liquid culture; Group 3: received 200 ml of autoclaved culture (Control). The supplementations were given weekly for four weeks (on days 1,7, 14 and 21). During the dosing period, the average daily gain of Group 2 was higher than in the Control group (444 g/d compared with 264 g/d; p < 0.05). Furthermore, the digestibility of organic matter increased in Group 1 and 2 compared with the Control (64.8, 64.0 and 60.4% respectively; p < 0.05), resulting in an increase in the total digestible nutrient (TDN) percent of ration (p < 0.05). But these effects disappeared post-dosing. There were also an increase in concentration of volatile fatty acids, trichloroacetic acid precipitable N and number of fibrolytic microbes in the rumen during the dosing period (p < 0.05), but these effects declined post-dosing. Results of Exp 2., where the encapsulated culture was applied at intervals of 4 d or 8 d for 120 d, showed that a shorter dosing frequency did not improve growth performance or feed intake. However, independent of the dosing frequency the growth rate of both groups fed the encapsulated culture were about 20% higher than in the Control group (p < 0.05). The present study showed that encapsulated fungi have a high potential to be used as feed additive at the farmers' level and that weekly dosing can increase growth performance of wheat straw based diets.