Effects of cross-inoculation from elk and feeding pine needles on the protozoan fauna of pregnant cows: occurrence of Parentodinium africanum in domestic U.S. cattle (Bos taurus).

Consumption of pine needles tends to cause abortion in domestic cattle but not in elk. The present study was undertaken to determine whether this difference was associated with the rumen microbial population. After emptying the rumen, pregnant cattle were inoculated with either elk or cattle rumen contents. For those cows fed the pine needle diet, there was no difference in abortion rate between those inoculated with rumen contents from either elk or cattle. Protozoal concentrations and number of genera were observed to decrease markedly in all cows fed the diet containing pine needles. The cycloposthiid ciliate Parentodinium africanum was observed in rumen contents from several of the domestic cattle (Bos taurus). Concentrations ranged from 1.4 to 130.6 x 10(4) per ml of rumen contents, which comprised 4.6 to 80.3% of the total ciliate population. Mean dimensions of this species were: length, 33.4 microns; width, 19.7 microns; length/width ratio, 1.70, which were similar to those previously reported for this species from Bos indicus in Brazil. This is the first observation of P. africanum, originally observed and described in stomach contents of the hippopotamus, either in Bos taurus or in any host in the northern hemisphere.