Influence de la température ambiante sur l'utilisation métabolique de l'énergie et de l'azote alimentaires chez le rat en croissance

Abstract

Summary. Effect of ambient temperature on the metabolic use of dietary energy and nitrogen in growing rat.Sixty-seven male rats of the Wistar CF strain were used in two trials to study the effect of ambient temperature on nitrogen and energy balances (experiment 1 ) and on the variations of certain biochemical parameters of metabolism (experiment 2). In both cases, the rats, housed individually in metal cages and fed ad libitum, were kept under three different temperatures : 21 °C (control), 3 °C (cold), 31 °C (hot).Compared to the controls, the rats at 3 °C showed a significant increase (P < 0.01) in food intake and a significant decrease (P < 0.01) in daily growth rate and feed efficiency ratio ; body fat content was unchanged. Compared to the controls, the rats at 31 °C showed a decrease (P < 0.01) in food intake and growth rate, a better feed efficiency ratio (P < 0.01) and a significant increase in carcass lipid content.When compared to rats at 21 °C, those at 3 °C had a much lower nitrogen retention ; at 31 °C this retention was only slightly lower. The urinary nitrogen excretion, increased by the cold temperature, reflected higher nitrogen catabolism, while its increase at a high temperature was probably due to a decrease in protein synthesis, and a subsequent degradation of excess ingested nitrogen. Energy retention increased (P < 0.01) as the ambient temperature increased from 3 to 31 °C, and wide variations in the amounts of fixed energy in the form of proteins or lipids were observed.The balance results obtained have been discussed in relation to the variations of some biochemical parameters of metabolism such as free fatty acids, free glycerol, lipoproteinlipase activity and in vitro utilization of labelled glucose.Introduction.

The Effect of Tropical Ambient Temperature on Growth and Metabolism in Pigs

“…Moreover, the N balance differences (Table 8) obtained in the same pigs, though not significant, had trends similar to those reported by Holmes (1973) and suggest a negative effect of T climate on protein deposition. In addition, the increase in urinary N of pigs in the T environment supports our previous data in rats (Christon, 1979) and might be related to amino acid degradation. In AL-fed finishing pigs in the T environment, the reduced intake of amino acids, and particularly of lysine, during the last half of Exp.…”

“…This might contribute to the elevated plasma concentration of these metabolites found in pigs reared in a T environment, especially when they are allowed to con-sume feed ad libitum (Table 7). In addition, adipose tissue lipoprotein-lipase activity increased in growing pigs kept in a hot environment; this agrees with prior results with rats (Christon, 1979). This could partly explain the increase and redistribution of fat depots in pigs kept in a hot environment.…”

“…Plasma glucose, protein, urea, free fatty acids (FFA) (Bergrneyer, 1974) and tissue lipo. protein lipase (LPL) activity as well as urinar} and creatinine concentrations were determinec as described previously (Christon et al, 1984) Total cholesterol and triglyceride concentra. tions were assessed by enzymatic techniques, using commercial kits 2.…”