|Abstract or Summary
- The objective of the thesis was to determine the effects of
isolated coumestrol on the growth, carcass characteristics and
certain organs of wether lambs. The first of two trials was conducted
over an eight week period with two groups of heavy wether
lambs. Trial two was conducted over an 11 week period with two
groups of four light wether lambs. Ration coumestrol contents were
112 ppm in the first trial and 145 ppm in the second trial. Due to
the difficulties and expense involved in preparing a large quantity
of coumestrol, only a small number of animals could be used.
The treated lambs in trial one gained slightly more than the
controls. In trial two, the treated lambs gained virtually the same
as the controls. Statistical analysis showed that in neither case
were the growth, feed conversion, carcass and organoleptic differences
Marked evidence of an estrogenic effect was apparent when the organ weights were compared. The liver weights of the control
and treated groups within each trial were similar. Although not
significant, the pituitary weights were consistently greater for the
treated lambs. In trial two, the seminal vesicle weights and teat
lengths of the treated lambs were significantly greater than the controls.
Measurements of these organs were not taken in trial one.
When compared to other studies, the increase in the weights of the
seminal vesicles is greater than that which occurs when lambs
are implanted with 3 mg of diethylstilbestrol.
The apparent anomaly between the lack of a consistent growth
response and the marked increase in seminal vesicle weight and teat
length is difficult to explain. Realizing that only a limited amount of
data was taken, speculation based on this data and data presented by
other workers indicated that coumestrol may not necessarily affect
an animal's system in the same order or at the same rate as diethytstilbestrol.
Since the levels of coumestrol fed were equivalent to low
levels of diethylstilbestrol (less than 0.15 mg), one would have expected
only small changes in the weights of the seminal vesicles. If
coumestrol was fed at levels which approach the equivalent of 2 mg. of
diethylstilbestrol, it is quite possible that an animal would be adversely affected. A rectal prolapse which occurred in the tast trial substantiates
this possibility to some extent.
That coumestrol at the administered levels can produce a slight growth response is probable, but the limited number of animals
used precludes a conclusive statement. Past experiments at the
Oregon Station, particularly the earlier ones, support this probability.
In evaluating the activity of coumestrol, the influence of inhibitors,
potentiators, additional estrogens, storage conditions, metabolic
estrogenic changes, pathogens and a variety of unknown factors
should not be overlooked. Evidence that such factors may have partially
obscured the results of the trials reported herein and past experiments