Page 559 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

534 CHAPTER 2

VetBooks.ir Table 2.5 Pharmacological agents used to alter sexual function in the stallion

DRUG DOSAGE THERAPEUTIC EFFECT ADVERSE EFFECTS
Testosterone 50 mg s/c every 2nd day for 7 days Increases libido Decreased semen quality; decreased
endogenous testosterone
production; increased aggression
GnRH 50 μg s/c 2 hours and 1 hour before Increases libido by increasing Frequent use or overdosage may
breeding endogenous testosterone decrease semen quality
Imipramine 0.5–2.5 mg/kg p/o 2 hours before Lowers ejaculatory threshold Mild sedation; dark coloured urine
breeding
Diazepam 0.05 mg/kg (up to 20 mg max.) slow Reduces anxiety Sedation and ataxia; disinhibition of
i/v 5 minutes before breeding aggressive behaviour
Phenylbutazone 6 mg/kg i/v 1 hour before breeding or Relieves pain Gastrointestinal and renal damage
2 mg/kg p/o q12 h on an ongoing with chronic administration
basis
GnRH vaccine Not documented Temporary sterility; dosage, Does not eliminate sexual or
efficacy and reversibility not aggressive behaviour in mature
evaluated in stallions stallions; repeated dosing may
result in vaccine reactions

Table 2.6 Performance-altering drugs with potentially negative effects on male fertility

DRUG COMMON USE EFFICACY ADVERSE EFFECTS
Progestagens (altrenogest) Decrease sexual behaviour Poor Temporarily decreases testicular size,
libido, testosterone levels and semen
quality. May cause permanent decreased
fertility if used in immature stallions
Phenothiazines Tranquillisation, Undocumented Priapism, loss of erectile function
(acepromazine, fluphenazine) control unruly behaviour
Reserpine Control unruly behaviour Undocumented Penile paralysis, loss of erectile function
Anabolic steroids (boldenone Improve athletic Undocumented Severe decline in testicular mass and
undecylenate, nandrolone decanoate) performance semen quality

AGGRESSIVE BEHAVIOUR is heritable, and some breeds and lineages are more
challenging to handle than others. Psychological
Definition/overview causes of aggression are often based on frustra-
In many cases of owner reported aggression, the stal- tion due to inappropriate management conditions.
lion is exhibiting normal equine behaviour; however, Unruly stallions tend to be handled as little as pos-
the handling of the animal or the available facilities sible and may spend a large amount of time isolated
are poor. In other cases, behaviour may have esca- from equine and human contact, further increasing
lated to unruliness because of inappropriate man- aggression. Overuse of stallions and semen collec-
agement. Stallions can be dangerous and evaluation tion during the non-breeding season may result in
should be carried out by experienced personnel in a increased aggression.
controlled environment.
Clinical presentation
Aetiology/pathophysiology Veterinary evaluation of an aggressive stallion is
Aggression in stallions can be caused by a number often precipitated by an injury to a person or horse.
of physical and psychological factors. Temperament Usually, stallions presented for aggression are