Level of energy intake affects the estrous-cycle in Sundevall's jird (Meriones crassus)

Effects of energy intake on the estrous cycle of the desert gerbillid, Sund evall's jird (Meriones crassus; 80 g; n = 2) were studied. Females were off ered either maintenance or below maintenance levels of millet seeds and ad lib. Atriplex halimus leaves and stems; drinking water was not available. V aginal smears were used to determine sexual stage. We hypothesized that the estrous cycle ceases at low levels of energy intake and commences when suf ficient energy is available. Females lost body mass linearly with a decreas e in metabolizable energy intake. Estrous cycle averaged 4.46 d at maintena nce energy intake but increased to an average of 7.81 d at 70% of maintenan ce energy intake. A cessation of the cycle occurred at an energy intake bel ow 70% of maintenance requirements, which resulted in a body mass loss of m ore than 1% per day. More variability in the length of the different stages of the cycle was found with lower levels of energy intake. When offered ad lib. millet seeds and A. halimus (n = 14), recovery to the normal cycle wa s attained within 10 d by 43% of the females and within 16 d by the rest of the females. Recovery time was longest in females that previously had the lowest energy intake. We concluded that the estrous cycle of M. crassus is sensitive to energy intake. With restricted energy intake, the estrous cycl e and reproductive activities cease but can be restored with provision of a dequate energy. This strategy ensures that reproduction occurs when conditi ons of food availability and body condition of the females are favorable.