46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
61
Group 2 using an unpaired t test. Significance was defined as P<0.05 and data are
presented as mean °” s.e. All statistical analyses were conducted using GraphPad
Prism Version 5.0 for Macg.
Results
The proportion of mares determined to be cycling, transitional or anoestrus was not
different between Group 1 and Group 2 (P = 0.314), Group 1 and Group 3 (P = 0.11),
or between Group 2 and Group 3 (P = 0.532) in mid November (Fig 2). At the end of
the trial there was a difference in the proportion of mares exhibiting oestrous
cyclicity between Group 1 and Group 3 (87.5% vs. 21%, respectively; P<0.0001) and
also between Group 2 and Group 3 (80% vs. 21%, respectively; P<0.0003). There was
no difference in oestrous cyclicity between Group 1 and Group 2 (87.5% vs. 80%,
respectively; P = 0.335). Figure 3 illustrates the reproductive status of each group on
10 February.
The number of mares determined to have ovulated was not different between Group
1 and Group 2, or between Group 1 and Group 3, on 20 January. However, a
difference was observed between Group 2 and Group 3 (P = 0.014) indicating that
more mares wearing light masks had ovulated than in the nonlight exposed control
group at this time. On 6 February, there was no difference in number of mares that
had ovulated between Group 1 and Group 2 but significant differences existed
between Group 1 and Group 3 (P<0.001) and between Group 2 and Group 3 (P<0.001,
Fig 4).
Mean serum progesterone levels were significantly higher in mares classified as
‘cycling’ (n = 38) compared with ‘noncycling’ mares (n = 16) in samples collected
after 1 January (P<0.0001). There was no significant difference in mean hair loss
scores between Group 1 and Group 2 (3.06 °” 0.17 vs. 2.95 °” 0.195, respectively; P =
0.665), with moderate hair loss observed in both. Ophthalmic examinations prior to
and after the study revealed no effect of treatment on eye health.
Discussion
Artificial advancement of the equine breeding season has become standard
management practice for Thoroughbred breeders.
This study shows that the reproductively active period of a nonpregnant mare can be
advanced using low-level blue light to one eye fromhead-worn light masks and that
this method is as effective as maintaining mares indoors under artificial lighting.
While it was expected that a high proportion of mares in the barn-lit and light mask
wearing groups would be cycling by the end of our study, what was surprising was
the large proportion of mares from these groups that were still reproductively active
at the beginning of the study in mid November. As reproductive examinations are
not commonly carried out at this time of year, it is often assumed that mares enter
winter anoestrus earlier in the year. However, we observed a transition to
anoestrus that occurred between late December and early January in the mares that
were still expressing cyclicity at the start of the study in our control group. Of
interest is that a lower proportion of mares from Group 3, the control group, were
still expressing oestrous cyclicity at this time. It is believed that the maintenance
history of each of the experimental groups contributed to their reproductive status
at the beginning of the study. Due to the size of the study, it was not possible to
randomly allocate mares into 3 groups from a homogeneous population. The control
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