Efficient breeding management of a stallion requires attention not only to reproductive parameters but to more general issues of health, nutrition and psychological well-being.
Each of these can have an impact on a stallion’s stud career. For example, orthopedic problems can negatively impact the stallion’s ability to mount a dummy or mare whilst mis-handling of the stallion can result in psychogenic loss of libido.
Efficient breeding management of stallions also requires careful management of broodmares, including choice of mares, and consideration of the technique of breeding and management so that a stallion is not being over-worked at any point during the stud season since this can result in reductions both in fertility and in libido.
Subfertility (reduced fertility) or infertility (absolute lack of fertility) in the stallion has many potential causes.
All stallions should be screened at the start of each breeding season for venereal diseases, which are a potential cause of subfertility.
Treatment will depend on the cause.
An accurate diagnosis of the cause of subfertility or infertility is therefore necessary.
Infertility is by definition absolute and not treatable. Subfertility may be treatable so that fertility can be restored to a commercially viable level or allow specific management procedures for a reduced but acceptable level of breeding.
The basis of efficient reproductive management of a stallion is to ensure that he is able to deliver ‘good quality semen to the right place at the right time’.
The detail of the management of a stallion for reproductive efficiency will vary depending on whether he is being used in a ‘natural cover’ or artificial insemination system Reproduction: artificial insemination.
An artificial insemination system Reproduction: artificial insemination puts less physiological demands upon a stallion as a single ejaculate from a single collection can be split to be used on multiple mares. In a natural cover program, each individual mare has to be mounted and mated.
Busy stallions in ‘natural cover’ systems, eg popular Thoroughbred stallions Thoroughbred, may be required to cover mares routinely 2-3 times a day for many weeks. However, at busy times this may increase to higher levels (4-6 covers/day). This can make ‘natural cover’ stallion management difficult as the demands can vary during the breeding season and at short notice depending on the mares coming through, eg as foaling mares come forward for covering on top of the barren and maiden mares there is a surge in numbers queuing for the available covering slots.
Clinical suspicion of infertility or subfertility may be historical or may become apparent in the course of a breeding season when more mares than expected are diagnosed not pregnant at a first ultrasonographic pregnancy examination, or if mares start exhibiting signs of venereally transmitted disease shortly after covering Female: bacterial venereal disease screening.
When assessing and managing a stallion’s fertility, it is important to take account of non-stallion factors, eg the fertility of the mares being bred to the stallion and management factors such as whether the timing of breeding is optimal in relation to when the mare ovulates.
Some causes of subfertility are obvious, eg kicks to the external genitalia resulting in inflammation and trauma Scrotum: trauma, failure to breed mares due to lack of libido Male: lack of libido or other clinical disease.
Some causes are easier to detect in some management systems than in others, eg a failure to ejaculate Male: ejaculatory dysfunction will be more apparent when semen is being collected using an artificial vagina than when ‘natural cover’ is being used Semen: collection.
Other causes are only explained following extensive work-up.
Diagnosis of infertility/subfertility
A wide range of diagnostic tests are available in equine reproduction, including:
de Oliveira R A & Aurich C (2021) Aspects of breeding stallion management with specific focus on animal welfare.J Equine Vet Sci107, 103773 PubMed.
Turner R M (2019) Declining testicular function in the aging stallion: management options and future therapies. Anim Repro Sci207, 171-179 PubMed.
Other sources of information
Blanchard T L (2011) Management of Subfertile Stallions under Natural-Mating Conditions. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley Blackwell, UK. pp 1240-1249.
Conboy H S (2011) Management of Stallions in Artificial Insemination. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley Blackwell, UK. pp 1198-1208.
McKinnon A O, Squires E L, Vaala W E & Varner D D (2011) Stallion Management. In: Equine Reproduction. Wiley Blackwell, UK. pp 1175-1261.