Mean serum progesterone concentrations from
samples collected on 6 January, 20 January and 10
February were compared between mares classified
as cycling or anoestrus across all groups using the
Mann–Whitney t test for nonparametric data. The
hair loss scores from Group 1 were compared with
the hair loss scores from 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.
Figure 1
progesterone concentrations were determined using
a competitive binding enzyme-linked immunosorbent
assay as previously described [21]. All reagents were
purchased from Sigma-Aldrichf. Inter- and intraassay coefficients of variation were 16.1% and 12.8%,
respectively.
Data analysis
Mares from each group were classified as either
cycling, transitional or anoestrus on 20 November
and 10 February (the beginning and end of the
study period). Pairwise comparisons were conducted
using a Chi-squared and Fisher’s exact test. The
number of mares within each group determined to
have ovulated by 20 January and 10 February was
calculated and pairwise comparisons were conducted
using a Chi-squared and Fisher’s exact test.
20
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.
• Equine Health Update •