Importance of feeding time in pair-fed, ovariectomized rats

The present investigation was designed to determine the effects of feeding time on body weight gain in ovariectomized (OVX) rats pair-fed with sham operated control rats. In pair feeding, a test and a control rat were each fed the same amount of food. In the first experiment, OVX rats and controls were pair-fed at 1900, just before the dark phase of the light-dark cycle. Body weight gain was observed for 36 days. There was no significant difference in weight gain between the two groups. In the second experiment, when rats were pair-fed chow, starting from 1200, there was a significant increase in the body weight of the OVX group compared to the sham operated control group. Observation continued for 56 days. In the third experiment, the OVX group in the pair-fed condition and the sham control group were pair-fed at 1900 for 56 days and feeding was then switched to 0500 (just before the beginning of the light cycle) for 28 days. The body weight gain in the OVX pair-fed group was quite similar to that of the sham control group when feeding started at 1900, but a significant increase in body weight gain of the OVX group was observed after switching the starting time of feeding to 0500. In conclusion, the results suggest that the time of daily feeding may be important for body weight gain during the dynamic phase after ovariectomy.