Diurnal variations in number of ciliate protozoa in the rumen of sheep fed once and twice daily

SUMMARY Diurnal changes in number of protozoa were examined in two wethers fed once and twice daily with 0·4 kg of concentrate and 0·4 kg of hay per day. The number of protozoa varied from 4·8 × 105 to 12·5 × 105 cells/ml of rumen fluid, depending on the feeding frequency and time of the day.Entodiniaformed 96·3%,Holotricha2·0%,Diplodinia1·3%, andOphryoscolex0·4% of the total counts. All taxonomic groups of protozoa reached maximum concentration immediately before feeding and decreased by about 60·80% during 4·12 h after feeding. Larger decreases occurred in animals fed once daily. Rumen fluid volume varied from 3·12 to 4·47 l but in different ways due to feeding frequency. Diurnal patterns of dilution rate of rumen fluid were the same in animals fed once and twice daily, showing the decrease from 0·98 1/h at 09·00 h to 0·311/h at 01·00 h. It is suggested that some factors other than dilution rate may be responsible for the decrease of protozoa after feeding.