EQUINE BEHAVIOR AND WELFARE: THE PMU CONTROVERSY
Katherine Houpt, Kevin Kunkel, Jennifer Johnson, Virgilla Tegiacchi and
Allen Bregman. College of Veterinary Medicine, Cornell University, Ithaca,
US.
Tens of thousands of pregnant mares each year are used to produce urine
for use as an estrogen source (Pregnant Mare Urine or PMU) for post-menopausal
women. The conditions under which these mares are kept has been criticized
by some animal rights groups who have brought the situation to the attention
of the public. The most controversial aspects of the production system
are water restriction, straight stall confinement and lack of exercise.
In order to determine objectively if any or all of these were stressful
or physically harmful to the horses, we compared the behavior and fluid
balance of mares when water restricted and when confined and exercise restricted.
In the first experiment, six mares were water restricted from ad libitum
(6.9 L/100 kg body weight) to 5, 4 and 3 L/100 kg body weight. Each level
of restriction was imposed for a week. When restricted, the mares were
clinically dehydrated based on skin turgor, and their plasma osmolality
rose from 283 + 1 mosmol/kg to 293 + 3 mosmol/kg. The mares ate less and
lost weight, but plasma cortisol did not increase. In the second experiment,
8 mares were confined for 6 months in straight stalls. Four were exercised
by release in a paddock as a group daily for 30 min. The other four mares
were exercised once every 14 days. Weekly 24 hr videorecording was used
to compare the behavior of the two groups. While stalled the exercised
mares spent less time standing than the non-exercised horses (44 vs 53.1%).
When released in the paddock after two weeks of confinement the mares trotted
more (12.4 vs 2.7%) and grazed less (8.4 vs 18.5%) than those who were
exercised daily. There was no difference in cortisol levels between the
groups. The most interesting finding was that only two of 8 mares lay down,
and then for less than 0.1% of the time. The horses would apparently enter
REM sleep on their feet and catch themselves or fall to their knees. Supported
by 96-35204-3673 NRI Competitive Grants Program/USDA