Caloric Uptake and Cold Resistance in Cold-Acclimated Rats Fed Commercial Chow or Semipurified Diet

Abstract

DESLAURIERS, R., ZOAMI, J., MGCULLOUSH, R. S., and H~ROUX, 0. 1941. Caloric uptake and cold resistance in cold-acclimated rats fed commercial chow or semipurified diet. Can. J. Physiol. Pharmacol. 49,[707][708][709][710][711][712] Sprague-Bawley male rats fed Master Lab cubes (MLC) or a semipurified diet (T4F) were kept for periods of 1-2 weeks at six subsequent temperatures: 28 "C, 22 "C, 6 "C, 0 "C, -10 "C, and -20 "C. Caloric balance, growth, body temperature, and survival were measured. As previously observed under outdoor winter conditions, with constant laboratory conditions T$ diet was still found to be superior to MLC in allowing a greater degree of cold resistance. At temperatures below 0 "C, in spite of a lower gross energy uptake, T4F-fed rats maintained a faster growth and a higher body temperature than MLC-fed rats, which suggests a greater heat conservation in these animals. Failure of MLC-fed rats to raise their gross energy uptake at -10 "C to a higher level than at 0 "C, and death of most of these animals at -28 "C within the first 3 days strongly suggest a physical limitation in the quantity of high bulk RlLC diet which can be consumed every day, hence a limitation in energy uptake increase. The ability of T,F-fed rats, on the other hand, to raise energy uptake in a continuous linear fashion as temperature is reduced, and their capacity to draw on energy reserves and to survive longer at -20 "C reflect greater metabolic potentials in this group than in MI,C rats. DESLAURIERS, R., ZOAMI, J., MCCWLLOUGH, R. S., et HB~owx, 0. 1941. Caloric uptake and cold resistance in cold-acclimated rats fed commercial chow or semipurified diet. Can. J. Physiol. Pharmacol. 49, 707-712.Des rats m3es Sprague-Dawley nourris avec des cubes '"aster Lab" (MLC) ou soumis au rtgirne semi-purifit (TaF) ont ttk maintenus de 1 B 2 semaines B des temptratures substquentes de 28 "C, 6 "C, 22 "C, 0 "C, -10 "C, et -20 "C. L'appsrt calorique, la croissance, la temptrature du corps et la survie ont Ctt mesurCs. Comme on avait dkj8 pu l'observer l'hiver B IYext6rieur, dans des conditions de laboratoire constantes, le rtgime (T4F) s5est encore montrt suptrieur aux cubes (MLC) pour la rtsistance des rats au froid. Pour les temperatures inftrieures B 0 "C, malgrt la quantitk plus faible d'knergie brute utiliste, ou emmagasinte? par le corps, la croissance des rats soumis au rtgime (T4F) a t t t plus rapide et la tempkrature de leur corps plus tlevte que dans le cas des rats nourris aux cubes (MLC) ce qui conduit penser que ces derniers conservent moins bien leur chaleur. Le fait que les rats nourris avec des cubes (MLC) n'ont pas pu augmenter la quantitt d'knergie brute utiliste, ou emmagasinte, pas leur corps B -10 "C par rapport B celIe correspondant B 0 "C et le fait que ces rats sont pour la plupart morts i i -20 "C en moins de 3 jours induisent B penser que ces rats ont deg difficultts pour consommer le volume nkcessaire de cubes (MLC), caracttrists par un grand volume pour une tnergie donnke et, de ce fait, ne peuvent disposer ...

Winter Ecology of Small Mammals

“…A lack of response to hyperphagy by digestive processes has also been reported in laboratory rats (Deslauriers et al, 1971), and it appears that the uptake of energy in the digestive tract is dependent on the inherent digestibility of the food item and is not adjustable by the individual.…”

Seasonal Changes in Catecholamine Content and Composition of Interscapular Brown Fat in Rats Fed a Commercial Chow or a Semipurified Diet

“…In spite of an apparently normal thyroid activity, T4F-fed rats show, however, a significantly greater degree of cold resistance than MLC-fed rats (Hdroux 1969 ;Deslauriers et al 1971). After cold acclimation, T4Ffed rats exposed to severe cold conditions maintained homeothermy and had no peripheral cold injury whereas MLC-fed rats became hypothermic and suffered from severe frostbite (Deslauriers et a/.…”