Equine Health Update Issue 1 Volume 16 - Page 20

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 •