Abstract: Studies on the grazing rate of rumen protozoa were carried out under laboratory conditions using a technique of fluorescence-labeled bacteria, in Nov. 2006. Four Xuhuai goats were used in this experiment to provide rumen protozoa and bacteria. Two groups were designed as follows: one group was the whole bacteria which were marked using fluorescence through removing free bacteria from rumen fluid (WFLB); the other group was bacteria which were marked using fluorescence without removing free bacteria from rumen fluid (FLB). The result showed that, The grazing rates of rumen protozoa was 398.4cells/ (cell H) for the group with (WFLB), 230.4cells/ (cell H) for the group with (FLB); Conversed into bacteria-N, they were: 2.15pg N/ (cell H) for the group with (WFLB) and 1.24pgN/ (cell H) for the group with (FLB) respectively. Extrapolating the assimilation quantity of Nitrogen by ciliates on bacteria of Xuhuai goat, were 103.2 mg N/ (d capita) for the group with (WFLB), 59.5mg N/ (d capita) for the group with (FLB) respectively; It also could be estimated as protein loss, the protein micro-cycling were 0.645g Pr/ (d capita) for the group with (WFLB) and 0.372g Pr/ (d capita) for the group with (FLB) respectively, and finally fluorescence-labeled technique has a potential for research on the grazing rate of rumen protozoa.

Key words: rumen protozoa, grazing rate, bacteria-N, fluorescence-labeled technique