Effect of underfeeding on ovulation and the œstrous rhythm in guinea-pigs

Abstract

Under well-regulated food conditions the œstrous cycle in the guinea-pig is almost uniformly 16 to 17 days in duration.

Underfeeding with a diet of 20 grams of carrots per day produces a prolongation of the diœstrum and, at the same time, a congestion in the ovary and uterus and a degeneration of developing graafian follicles.

The extent of prolongation of the diœstrum depends upon the stage at which an animal is underfed.

Underfeeding during the first 5 to 7 days of the diœstrum has only a slight effect, postponing the next œstrus for one or two days, while underfeeding during the later part of the diœstrum gives much more marked results.

When an animal is underfed for 5 days, from the 12th to the 17th day after an ovulation and œstrus, the next ovulation and œstrus is delayed for about 7 days, being expressed at the 23d to 25th day instead of at the 17th.

Should an animal be underfed for 7 days, from the 10^th day to the 17^th day after estrus, the next ovulation and estrus is postponed for 10 to 11 days, arriving at the 27^th to 28^th day, instead of the 17th day.

This variation in the effect of the underfeeding when applied at different periods of the diaestrum is associated with the fact that the conditions of the ovary differ at the different times.

Shortly after an ovulation the ovary contains almost entirely small primary follicles. These follicles are not so unfavorably affected by food conditions as are the large graafian follicles, which begin their growth and development during later stages of the dimstrum.

A large follicle at the height of its development seems to require much better nutrition than a small primary follicle, and the lack of proper food arrests its progress very readily.