Post on 21-Aug-2015
Mismating also known as misalliance refers to situations in which an animal is bred in contrast to the wishes of the owner.
Unwanted mating or mismating is a common clinical problem in veterinary practice which may arise because dog owners are not aware that their pet is “in heat” or the owner may be aware of estrus but underestimated the will of a stud or bitch that wants to encounter the opposite sex. Therefore, even the best educated and most careful owners will end up with mismating problems in their bitches.
To determine whether mating has indeed occurred is to examine a vaginal smear.
If the dog was bred , one can almost always find sperm on the smear without much difficulty.
We can have the bitch ultra-sound scanned 35-40days after mating.
04/18/23
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MEDICINAL TERMINATION OF PREGNANCY
Modification of estrogen-progesterone ratio by administration of estrogen/synthetic estrogen derivatives /glucocorticoids.
Induction of functional luteal arrest or luteolysis by substances that act directly (prostaglandins) or indirectly on the CL by inhibiting luteotrophic support.
Blockage of progesterone secretion by inhibiting steroidogenesis (epostane)
Blockage of progesterone action at the receptor levels (anti progesterone (mifipristone / algepristone).
Stage 1: Canine Fertilization to Implantation
Occurs 18 days from the LH
Changes in estrogen:progesterone ratio or decline in corpus luteum progesterone secretion can lead to impaired implantation or abortion.
Drugs used to terminate pregnancy at this stage include:
estrogens: Estradiol benzoate, estradiol valerate
prostaglandins: inhibitors of progesterone secretion (epostane)
progesterone antagonists (mifeprestone, aglepristone).
Stage 2: Implantation to Fetal Ossification
Fetal ossification occurs at 40 to 42 days from the LH peak
Drugs used to terminate pregnancy at this stage include:
prostaglandins,
dopamine agonists/antiprolactinic agents (bromocriptine, cabergoline), antiserotoninergic (methergoline),
steroids (dexamethasone),
progesterone-secretion inhibitors (epostane)
progesterone antagonists (mifeprestone, aglepristone),
Stage 3: Fetal Ossification to Parturition
Prostaglandins reduce corpus luteum blood supply and luteal steroidogenesis. Abortion induction at this stage is likely to result in premature parturition and delivery of live pups.
Administration of Estrogen
• Estrogens exert their action by causing
• closure of the uterotubal junction,
• alter the transport time of zygotes
• exert direct embryotoxic effect resulting in implantation failure or embryonic death.
• Estradiol benzoate
• 0.5-3 mg/kg for one injection within 4 days of mating
• Estradiol valerate@3.0-7 mg once for 3-4 days
Estradiol benzoate @ 0.5 - 3.0 mg every other day for a total of three injections beginning 4 - 10 days after misalliance.
Estradiol valerate @ 3.0 - 7.0 mg administered once 4 to 10 days after mismating.
Contd
Risk after administration of estrogen
Pyometra
Metritis
Ovarian cysts
Aplastic anemia, bone marrow suppression
Alopecia,skin hyperpigmentation
Prolongation of estrus Clinically, > 60% bitches after an unwanted mating are not
pregnant
Prostagladins
Prostaglandins cause lysis of corpora lutea and decrease in plasma concentrations of progesterone.
Prostaglandins also produce contraction of smooth muscle having an ecbolic effect thereby inducing abortion
The bitches must be healthy and less than 7 years of age. Pregnancy must be confirmed using ultrasonography
Corpus luteum of the bitch are highly resistant to prostaglandins than those of other species.
Repeated therapy is necessary to achieve complete regression of the corpus luteum
Dinoprost ( lutalyse) :20-30µg/kg b.i.d for 4-7 day
Cloprostenol@2.5µg/kg for 4-7 days at alternate days
Given after 30 days of pregnancy
Contd:
Side effects
vomiting, diarrhea, pupil dilation, hyperpnoea, salivation, urination, anxiety and ataxia
Side effects can be reduced by concurrent
administration of anticholinergic drugs like atropine @ 0.5 mg/kg SC or IM, 15 minutes before prostaglandin administration
. Walking the animal for 30 minutes following PGF2 α injections would help to reduced intensity of side effects
Dopamine agonist
Prolactin is the major luteotropic hormone throughout the luteal phase in both pregnant and non pregnant bitches
Antiprolactin agents, with strong dopamine D 2 receptor agonist activity, have been used to induce abortion, from 30-40 days after LH surge.
Contd
Bromocriptine@20µg/kg b.i.d for 6 days
Cabergoline(cabgolin , camforte)@5µg/kg once daily for 5 days
PGF2 + Dopamine agonist
A combination therapy of oral cabergoline at 5 µg/kg per day and low dose of cloprostenol (PGF 2 α analogues) injection of 1 µg/kg SC every other day for upto 9 days terminated pregnancy in dogs when administered starting around day 28 of pregnancy.
The regression of the CL is achieved by double mechanism of action, Direct local effect of PG on CL steroidogenesis Indirect effect due to withdrawal of pituitary prolactin
Advantage: safe for the bitch
terminating pregnancy by resorption rather than by abortion
effective as early as 25 days after the 1st mating
All the treated bitches returned in heat and become pregnant and had normal litters. Thus, this treatment did not compromise the fertility of the treated animals.
Progesterone receptor antagonist
Mifepristone@2.5 mg/kg, sc, bid for 5 days after 32 daysMifepristone@2.5 mg/kg, sc, bid for 5 days after 32 daysAglepristone@10 mg/kg, sc, for 2 days 30 days after ovulationAglepristone@10 mg/kg, sc, for 2 days 30 days after ovulation
abortion within 4-7 daysabortion within 4-7 days
CORTICOSTEROIDS:
Dexamethasone when administered beginning at mid gestation can terminate pregnancy in dogs by activating endogenous mechanisms similar to those involved in parturition.
Injectable Dexamethasone (5 mg twice daily IM for 10 days)
oral Dexamethasone (0.1 to 0.2 mg twice daily at a decreasing dose for 5 to 10 days
Side effects: polydipsia , polyuria , vaginal discharge, restlessness, anorexia or vomition
Miscellaneous drugs…
Epostane :
A steroid molecule that inhibits steroid synthesis at the level of the hydroxy steroid – dehydrogenase isomerase enzyme system, thereby inhibiting the formation of progesterone from pregnanolone .
It terminates pregnancy when given orally at 2.5 to 5 mg/kg for 7 days starting any time after diestrus