Predicting Breeding Soundness in Pre-, Peri- and Postpubertal Colts

Background:

  • The study aimed to identify parameters for predicting breeding soundness in colts at the youngest possible age
  • Rearing colts for breeding is costly; early prediction of future fertility has significant economic value

Study Design:

Predicting Breeding Soundness in Colts - Pre-, peri- and post-pubertal colts standing in a field with descriptors

  • 46 Warmblood colts examined at approximately 6 months, 20 months, and 30 months of age
  • Assessments included: body condition scoring, weight, and testicular palpation, ultrasound and volume measurement
  • Blood sampling before and after human chorionic gonadotropin stimulation (5,000 IU intravenously)
  • Hormones measured: anti-Müllerian hormone (basal) and testosterone (at 0, 2, 24, and 72 hours post-stimulation)
  • 12 stallions at 2.5 years were evaluated for sperm quality; grouped by testicular volume and palpation findings

Key Results:

  • No significant difference in morphologically normal or progressively motile spermatozoa between groups
  • Stallions with small testes showed lower membrane-intact spermatozoa and higher acrosome reaction rates
  • Body condition score positively correlated with progressively motile spermatozoa (r=0.765, p<0.05)
  • Anti-Müllerian hormone was highest in peripubertal colts; did not differentiate abnormal from normal testes
  • Human chorionic gonadotropin stimulation increased testosterone most strongly in postpubertal stallions at 72 hours

Conclusions:

  • Early predicting breeding soundness in colts from pre- or peripubertal parameters is not currently possible
  • Palpatory findings and testicular size are inconsistent in young colts, except in cases of cryptorchism
  • Body condition score meaningfully influences sperm quality in postpubertal stallions and warrants monitoring

(Köhne M, von Rintelen-Feldmann A, Papkalla M, Tönissen A, Martinsson G, Schmicke M, Sieme H. 2025. Prediction of breeding soundness in pre-, peri- and postpubertal colts. JEVS 145:1052958 – Presented in Association with and by Permission of the International Society for Equine Reproduction)