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Table 1 Pre-ovulatory follicular growth rates: a comparison between the first ovulation after winter anoestrus and later ovulations in the same mares

From: Growth rate of ovulatory follicles during the first ovulatory oestrus (after seasonal anoestrus) and subsequent oestrous period in Irish Draught mares

  Follicle diameters up to 11 days before ovulation (mm)
Days before ovulation −11 −10 −9 −8 −7 −6 −5 −4 −3 −2 −1 0
First ovulations of the season
Jan 14th to Feb 22nd
No. of observations 15 16 16 16 16 16 16 16 16 16 16 16
Mean diameter 20 23.5 26 27.7 30.1 33.1 34.3 36.2 39.1 41.7 43.5 44.6
Feb 25th to May 22nd
No. of observations 16 16 16 16 16 16 16 16 16 16 16 16
Mean diameter (mm) 20.3 22.3 25 27.5 30.1 33.3 35 38 40.2 42.1 42.7 44.8
Jan 14th to May 22nd
Total no. of observations 31 32 32 32 32 32 32 32 32 32 32 32
Mean diameter (mm) 20.1 22.9 25.5 27.6 30.1 33.2 34.6 37.1 39.6 41.9 43.1 44.7
Range (mm) <10-36 <10-37 10-41 10-43 10-44 12-45 15-48 18-48 20-53 25-55 31-57 35-59
Subsequent ovulations
Jan 15th to Mar 12th
No of observations 2 4 3 4 9 5 11 11 14 15 14 17
Mean diameter (mm) 19 24.8 20.3 25.8 28.2 32.6 34.7 36.6 39.3 41.9 44.8 44.2
Mar 14th to June 16th
No. of observation 3 3 3 5 5 8 7 11 13 14 17 17
Mean diameter (mm) 26 23.6 29.2 28.2 31.4 30.4 33.7 36.5 39 41.5 41.6 42.8
Jan 15th to June 16th
No. of observations 5 7 6 9 14 13 18 22 27 29 31 34
Mean diameter (mm) 23.2 24.3 24.8 27.1 29.3 31.3 34.3 36.5 39.1 41.7 43 43.5
Range (mm) 14 - 32 17 - 34 18 -36 16 -37 15 -41 23- 39 24 - 43 24.5-47 26 - 52 27.5-52 31.5-55 31-57.5
Difference in mean diameters −3.1 −1.4 0.7 0.5 0.8 1.9 0.3 0.6 0.5 0.2 0.1 1.2
Mean growth rate (mm/day) Day −11 to 0   Day −8 to 0   Day −5 to 0        
First ovulations 2.20   2.14   2.02        
Subsequent ovulations 2.19   2.37   1.84        
Difference 0.01   0.23   0.18