Preliminary study on the effect of exposure to low temperature on the viability of both mixed and monocultures of rumen protozoa

Abstract

The effect of low temperatures on the viability of rumen protozoa was studied. In Trial 1, samples of mixed rumen contents were diluted and cultured at 38, 15 and 5°C for 2, 4 and 6 h, respectively. Viability of Isotrichidae was not affected by either the length of incubation or the temperature (P < 0.10). Incubation at low temperatures negatively affected the viability of Entodinium, Diplodiniinae and Ophryoscolex. Differences between 15 and 5°C were not significant except for Entodinium spp. (P = 0.07). The reduction of viability increased with time, this effect being noticeable (P < 0.10) for Entodinium (after 4 and 6 h), Diplodiniinae (at 6 h) and Ophryoscolex (at 2 and 6 h). Preservation of mixed rumen protozoa for at least 4 h at 15 or 5°C did not markedly affect viability, suggesting that cultures can be recovered after short-term refrigeration. In Trial 2, monocultures of Entodinium caudatum and Diploplastron (Metadinium) affine were cultured at 5°C for 4, 8 and 24 h with or without milk powder/egg yolk solution as a membrane protector. For both species, viability was not affected after 4 h at 5°C, but decreased from 8 h onwards (P < 0.01). The use of a membrane protector improved viability of D. affine at all time periods (P < 0.05), but only at 24 h for E. caudatum (P = 0.07), showing that the use of membrane protector may be positive at medium or long exposure to low temperatures, depending on the species.

This work has been financed by the Project AGL 2004-02910 (CICYT, España). Dr. Manuel Pérez Quintana was supported by a MAE fellowship. Thanks are given to Prof. B. A. Dehority for his critical review of the manuscript.