2. Induction of oestrus in the bitch and queens

What are the indications for inducing oestrus in bitches and queens?

1. Pathological anoestrus (primary or secondary)

2. Hunting or show dogs with altered body fat and decreased gonadotropin secretion

3. Cushing's (cycle failure) or hypothyroidism (rare cycle)

What must be done before inducing oestrus in a bitch or queen?

1. Complete examination including reproductive history, uterine evaluation, mammary gland palpation, vaginal cytology

2. Routine blood work

3. History of management and activity level

What non-pharmacological method can be used to induce oestrus in a bitch?

Dormitory effect – housing with bitches in oestrus (pheromones induce oestrus)

What is a risk associated with using pharmacological methods to induce oestrus in bitches?

Risk of small litter size

What are examples of pharmacological methods to induce oestrus in bitches?

1. GnRH agonists

2. Gonadotropins

3. Oestrogens

4. Dopamine agonists

How do GnRH agonists induce oestrus in bitches?

They cause pituitary release of LH and FSH, followed by fertile oestrus and spontaneous ovulation

What is the success rate of pregnancy in bitches treated with GnRH agonists?

50-100% of cases

What is an example of a GnRH agonist used to induce oestrus in bitches?

Deslorelin implants

How are deslorelin implants administered in bitches?

Near the umbilicus

When does oestrus typically occur after deslorelin implant application in bitches?

2-15 days

When does ovulation typically occur after deslorelin implant application in bitches?

12 days

What action should be taken if ovulation does not occur within 20 days of deslorelin implant application in bitches?

Remove the implant

What is the maximum duration a deslorelin implant should be left in a bitch?

40 days

What is the risk of leaving a deslorelin implant in a bitch for longer than 40 days?

Risk of prolonged oestrus

What are examples of gonadotropins used to induce oestrus in bitches?

FSH, LH, eCG, and hCG

What do gonadotropins such as FSH, LH, eCG, and hCG do in bitches?

Stimulate ovarian response followed by fertile oestrus and either spontaneous or induced ovulation (ovulation often fails)

What does equine chorionic gonadotropin act like in bitches?

FSH, stimulating follicular growth

How do oestrogens induce ovulation in bitches?

Positive feedback on GnRH, causing an LH surge

What are examples of dopamine agonists used to induce oestrus in bitches?

Anti-prolactin (Cabergoline/Bromocriptine)

How do dopamine agonists induce oestrus in bitches?

They decrease prolactin, provoking hypothalamic or pituitary hormone responses → luteolytic effect, leading to premature pro-oestrus and fertile oestrus

What is the standard dose of dopamine agonists used in bitches?

5 μg/kg/day until pro-oestrus or for 30-40 days

What is the success rate of inducing pro-oestrus and pregnancy using dopamine agonists in bitches?

Pro-oestrus 80-100%, pregnancy 60-100%

Why is artificial induction of oestrus rarely indicated in queens?

Risk of hyperstimulation and natural methods are preferable

What non-pharmacological methods are preferable for inducing oestrus in queens?

Increase daylight and housing with other cycling females or a tomcat

When can hormones be administered to queens?

Only during inter-oestrus or anoestrus

Why should hormones not be given to prepubertal queens?

Risk of cystic follicles