Individual housing influences certain biochemical parameters in the rat.

Individual housing has been reported to modify animal behaviour. The present study compares the plasma levels of glucose, triglycerides and total cholesterol, weight, and food and water intake in two groups of female rats. Group A: 10 rats who remained grouped in two cages for 21 days; and Group B: 10 rats housed in two cages for 7 days, then isolated in individual cages from day 8 to day 15, and finally grouped together again for the last 7 days of the study. The results showed that the plasma values of glucose declined (P < 0.05) in the Group B rats when they had been returned to group condition (4.79 +/- 0.72 mM) than when they had been isolated (5.45 +/- 0.94 mM). Plasma triglyceride levels were lower (P < 0.05) in isolated rats (0.70 +/- 0.26 mM) than in any determination of the grouped rats. Group B: 1st week 1.21 +/- 0.21 mM, 3rd week 0.88 +/- 0.20 mM; and Group A: 1.22 +/- 0.20, 0.96 +/- 0.16, and 0.96 +/- 0.36 mM, in the first, second, and third week, respectively. There were no statistically significant differences in total cholesterol values as a function of the individual housing of animals. While there was no weight difference between the two groups of rats that could be ascribed to individual housing, there was a statistically significant increase (P < 0.05) in the food intake of isolated rats (17.5 +/- 3.2 g) with respect to values in the same Group B animals when they were housed together (1st week, 16.6 +/- 2.8 g; 3rd week, 16.8 +/- 3.1 g). These results therefore confirm that individual housing of female rats provoke variations in certain biochemical parameters, and that if this is not taken into account in performing different scientific studies, it could give rise to unreliable or even dubious results.