IN-VIVO AND IN-VITRO INVESTIGATIONS FOR N UTRIENT DIGESTIBILITY AND HEAT-PRODUCTION OF RUMINANTS UNDER HEAT-STRESS AND DIFFERENT NUTRITIONAL LEVELS .5. COMPARISON OF IN-VIVO AND IN-VITRO INVESTIGATIONS WITH RESPECT TO ENERGY-METABOLISM AND ENERGY CONTENT OF THE RATIONS

V. Comparison of in vivo and in vitro investigations with respect to e nergy metabolism and energy content of the rations. The in vivo and in vitro investigations were conducted to examine if the effect of diffe rent nutritional levels and increasing environmental temperature on th e digestibility of nutrients and heat production in ruminants leads to some changes in the composition of the digesta and the energy transfo rmation in rumen and if these effects can be reproduced in vitro (Comm unications 1-4). Despite of basic differences between the in vitro sys tem and the natural ruminal system in vivo, similar trends in relation to the changes in environmental temperature were observed in both the systems with respect to energy transformation, i.e. in incubation of the concentrate inoculum (in vitro) as well as in feeding of ration 3. It has to be presumed that feeding of a ration with high concentrate energy levels under heat stress leads to physiolgical conditions simil ar to symptoms of chronic tympany and results in to a reduction in the efficiency of the process of microbial synthesis. This could be the p ossible explanantion of at least a part of the discrepancies found in the nitrogen and energy balances under high environmental temperatures . This investigation has demonstrated that under heat stress the energ y metabolism of adult wethers is highly effected by the changes in the fermentation process. Almost all of the important in vivo effects of the increase in environmental temperature could be reproduced in vitro both in terms of their qualifies as well as magnitudes. Thus, this ex periment provides a methodological foundation which opens up the possi bilities of conducting the investigations of similar problems directly in the laboratory. The applicability of the results obtained to tropi cal field conditions, individuals with different production, managemen t or feeding levels, or to different species, remains yet to be invest igated.