Abstract
The number of ova ovulated after mating and the change in the ovulated ova were investigated on each of the first 4 days after ovulation in mice fed with three different levels of dietary protein. Adult female mice, ICR-JCL strain, with initial average body weights and ages of 30.3g (28.5-31.5g) and 60-65 days, respectively, were examined. The composition of diets, feeding conditions and protein levels in the diets accord with those in our previous report1). Female mice were mated with male mice of the same strain after a day, 10 days, 20 days and 30 days of feeding with the experimental diets, and the ovulated ova were observed morphologically through a 400×microscope after perfusion of the oviduct and uterine horn. The results obtained in the investigation are summarized as follows. 1) The number of ova ovulated in mice fed with either high or low protein rations decreased markedly as compared with that for the standard protein ration, and this result was independent of the length of feeding periods. 2) Abnormal ova were discovered in the oviducts and uterine horn of the mice in all experimental groups, while the number of abnormal ova in mice fed with either high or low protein rations increased from the 10th day of feeding with the experimental diets. 3) In all experimental groups, the number of abnormal ova in the oviduct over the tested period of 4 days increased with time. However, the trend in the control group was the least of all. 4) In each group, many experi- mental mice retaining abnormal ova were observed, but their numbers tended to increase particularly in mice fed with high or low protein level rations over 10 days. 5) It was observed that all ova were abnormal in some of the mice fed with the high protein ration for 30 days or more, or fed with the low protein ration for 20 days or more, while abnormal ova were observed in any mouse fed with standard rations. From the above results, it is concluded that the decre- ment in the litter size and the prolongation of the delivery interval in the mice fed with high or low protein rations, were caused by a decrement in the number of ovulated ova, by an increment in abnormal ova, and by infertility and failure of implantation resulting from the abnormality of all ova.
