Intrauterine Marbles Fail to Alter Estrous Cycles or Related Behavior

Intrauterine placement of marbles in pony mares did not change reproductive physiology or normal sexual or social behavior, according to a study conducted by researchers from the University of Liverpool.

The nine maiden mares used in the study were divided into two groups, a control group and a marble-implanted group. Researchers tracked hormone levels (luteinizing hormone, estradiol, progesterone, and testosterone), ovarian and uterine function, and behaviors generally associated with the estrous cycle.

Fifty complete ovarian cycles were evaluated, with 26 ovarian cycles monitored for the nine mares prior to treatment and a further 12 cycles were evaluated for mares in each of the groups post-treatment.

While the mares did not show any adverse side effects of marble implantation, no changes in reproductive physiology or behavior were noted.

Veterinary Journal published the original article, “The effect of intra-uterine devices on the reproductive physiology and behaviour of pony mares,” in August, 2009.