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The following may be noticed by the owner:
Normal gonadal development occurs at about embryonic days 10-12 in the rat as primordial germ cells migrate from the endoderm of the yolk sac through the dorsal mesentery to the coelomic epithelium of the gonadal ridge. The gonadal transformation into testes occurs once the the germ cells have associated with the sex cords within the gonadal ridge at about embryonic day 14. At this time fetal testes protrude into the peritoneal cavity (space within the abdomen) and appear as distinct organs.
Testicular migration, the process by which the testes descend into the scrotum, is a complex process in the rat. It is thought that the testes in rats descend passively as a result of the growth of the trunk and pelvis, but little or no growth of the connection of the testis to the scrotum (genitoinguinal ligament or gubernaculums). (1)
In rats, the testes normally lose their position in the abdomen and descend into the scrotum at approximately 15 days (1),(2) following birth. Testes that have not or do not descend may be retained in the abdominal cavity or the inguinal canal. It is important to note that throughout life male rats normally have open inguinal canals with a functional cremaster muscle that allows the testes (testicles) to migrate easily in and out of the abdominal cavity for both protection and temperature control.
Experimental fertility studies done with young male rats have shown no impaired fertility in in the presence of a developed undescended testis; but may be reduced in older male rats. However, spontaneously occurring undescended testes have the potential to be both underdeveloped and non-functional. In addition, undescended testes pose an increased risk of developing testicular tumors as well as testicular torsion and infarction and inguinal hernias. For these reasons castration (neutering) is recommended for cryptorchid rats.
*Note: Pet owners are advised not to place the male back in with a female cage-mate immediately after surgery due to the presence of viable sperm. References citing the timeline for post operative viable sperm, in rats, vary greatly from 8 days to 8 weeks post-op. Anecdotally, waiting 2-4 weeks post-op before placing a neutered male with an intact female has not resulted in any known pregnancies. However, a time frame of 6 weeks post neuter prior to placing a male rat with an intact female rat is most commonly practiced by pet rat owners.
It is important for pet owners to take this information into account when choosing to place the male back in with a female cage-mate, thus preventing unplanned litters.
Palpate for presence or absence of testes in scrotum.
Palpate abdomen for presence of undescended testis (testicle).
Note the following when surgery is considered:
Preanaesthetic fasting of rats is not necessary since vomiting does not occur in this species. Free access to both food and water should be provided until just prior to anesthesia (Flecknell, 1991).
Rats do experience pain with surgical procedures. The type of pain medication used post-op should be determined based on extent of procedure and the anticipated severity of pain.
For mild to moderate pain: Banamine (flunixin meglumine), Metacam (meloxicam), or carprofen. Do not use if a corticosteroid has already been prescribed. .
Consideration should be given to including a broad spectrum antibiotic post op, as prophylaxis, when performing an orchiectomy.
For information regarding medications refer to the Rat Medication Guide.
*Note: a juicy type of fruit also provides an additional fluid source in the diet.
Posted on August 27, 2005, 16:38,
Last updated on November 17, 2014, 16:42