Relation of Temperature to Nutrition and Resistance.

Abstract

With our studies on the effect of external environment on susceptibility and resistance of animals to infection, we are also studying the indirect effect through the influence on the nutrition. We 1 found that rats fed high fat-containing diets (20-35% of the calory requirements) in the form of vegetable oil or cocose, showed marked loss in weight and other unfavorable symptoms as well as decreased resistance to infection. These effects appeared to be more marked during the summer than during the fall season of the year. We, therefore, undertook a more systematic study of the relation of external environment to nutritive requirements, namely the relation of temperature to the metabolism of vegetable fats.

The procedure consisted in observing parallel groups of rats kept at different temperatures and maintained on identical diets. The animals were about 6 weeks old at the start of the experiment and received a daily ration of 22 to 25 calories. The following is a typical experiment:

Four groups of rats, 3 males and 3 females per group, were used. Two of the groups were kept at a temperature range of 17-20°C. and the other two at 28-30° C. The diets were as follows:

The rats of cage I (animal house) and cage III (incubator) received daily:

The rats of cage II (animal house) and cage IV (incubator) received daily:

The results of average weight at 13 weekly intervals shows that while at 20°C. there is relatively little difference in the growth curves of the 2 sets of rats, at 28°C. the difference is quite marked.

At the end of the experiment these rats were infected with Tr. evansi. The results, summarized in Table I show that the duration of the infection parallels the growth curves.