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Comparison of in Vivo and in Vitro Techniques in Ruminology Studies¹

Departments of Dairy Husbandry and Microbiology, University of Maryland, College Park

ABSTRACT

This paper is concerned with the comparison of in vivo and in vitro rumen bacterial dissimilations of some carbohydrates, amino acids, and organic acids of metabolic importance. It was observed that succinate, DL-aspartate, glucose, and maltose were readily fermented by rumen microorganisms, and that volatile fatty acids (VFA) were produced. The amino acids DL-lysine, DL-alanine, and glycine were not degraded to an appreciable extent to VFA by rumen bacteria. In general, qualitative agreement between in vivo and in vitro washed cell suspension (WCS) experiments was obtained with DL-lysine, DL-alanine, and glycine, while the in vivo studies using DL-aspartate and succinate agreed with the WCS in vitro studies of Sirotnak et al. (17, 18). With the substrates glucose and maltose, in vitro WCS experiments were both variable and in disagreement with the in vivo studies. Thus, the WCS technique appears most useful for studying short one- or two-step reactions presumed to occur in the rumen. This technique loses significance when studying niultistep metabolic reactions and, in such cases, the results should be interpreted with caution until they are verified by in vivo experiments, or until further studies concerning the limitations of the WCS technique are available.

¹ Scientific Article No. A641, Contribution No. 2824 of the Maryland Agricultural Experiment Station.