title: The influence of mare numbers, ejaculation frequency and month on the fertility of Thoroughbred stallions.
abstract: OBJECTIVE
  Although considerable variation in per cycle pregnancy rates exists between Thoroughbred (TB) stallions, there is little information on factors that may influence this figure.
  
  
  OBJECTIVE
  To assess the influence of month, mare numbers and mating frequency on the fertility of TB stallions standing on studfarms in East Anglia, England.
  
  
  METHODS
  The daily breeding records of 31 TB stallions mating 3034 mares on 4851 occasions during the 2010 season were surveyed and related to first scan pregnancy rates. The influences of mare book size, month, number of matings per day and mating frequency or abstinence on per mating pregnancy rates were analysed.
  
  
  RESULTS
  The overall per mating pregnancy rate for all the stallions was 59.6%, but for individual stallions the figures ranged from 19.0% to 80.1%. The first mating occurred on 9 February and the last on 24 July and the per mating pregnancy rate per month was significantly reduced in June and July. The number of mares mated by individual stallions ranged from 15 to 161, giving a mean overall workload of 160 matings per 100 mares. The per mating pregnancy rate was not related to book size, the number of matings in the season or the mating frequency per day. However, some stallions showed differences in per mating pregnancy rate related to month or the number of ejaculations in the preceding 3 days.
  
  
  CONCLUSIONS
  The majority of TB stallions are able to maintain good fertility despite large books of mares. However, 5 of the 31 stallions surveyed showed a per mating pregnancy rate of ≤50%.
  
  
  CONCLUSIONS
  This survey has identified wide differences between the per mating pregnancy rate in TB stallions. Identification of the factors involved through more comprehensive surveys would provide useful information for mare and stallion owners.
authors.affiliation: The Paul Mellon Laboratory of Equine Reproduction, Brunswick, Newmarket, Suffolk, UK. pml@btinternet.com
authors.forename: W R
authors.initials: WR
authors.lastname: Allen
authors.forename: S
authors.initials: S
authors.lastname: Wilsher
mesh_terms: D000818:Animals; D001947:Breeding; D004542:Ejaculation / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D012621:Seasons; D013997:Time Factors; D006113:United Kingdom