by Douglas R. Mader, Carl. M. Palazzolo, William Ridgeway,
Gregg Perrault and Thomas Greek
The following questions were asked in relation to egg binding in chelonians. The answers reflect opinions based on current veterinary medical literature and personal experience in clinical practice. Please keep in mind that the causes of egg binding may be multifactorial, and that each individual case should be evaluated as an isolated condition. This is best left to individuals experienced with chelonian reproduction.
What is egg binding and why should it be treated?
Egg binding refers to the condition where a female oviparous animal is due to lay eggs, but because of some complication, is unable to do so. The result is that the eggs are retained within the body. This can be brought about by a number of factors.
One of the more common causes is where the egg is too large to pass through the pelvic canal. This can happen due to the internal development of an abnormally large egg, or in a condition where the pelvis has been damaged and because of this damage even normal sized eggs are unable to pass.
A second common cause of egg retention is related to behavioral stress. Many chelonians will not deposit their eggs if their habitat is not correct for oviposition (egg laying). Quite often incorrect housing, substrates and temperatures will inhibit animals from building nests and subsequently prevent egg laying. Many times, once these deficits are corrected the animal will readily build a nest and deposit the eggs without further problems.
Other factors involved with egg retention include improper nutrition, disease of the reproductive tract (e.g.. cancer, infection), prior damage to the reproductive tract (e.g.. scar tissue from previous surgery), imbalances of various reproductive hormones and general poor health of the animal.
Retained eggs must be removed because if left they can cause serious disease, and ultimately death to the affected female. Retained eggs put excessive pressure on the internal organs of the body such as the liver and stomach. This can make it difficult for the animal to eat thus adding nutritional stress to an already compromised animal.
The retained eggs may cut or otherwise injure the internal structures of the animal, and the free egg material within the body cavity can potentially cause a lethal condition called egg peritonitis.
If eggs are left inside the female too long before removal there may be irreversible damage done to the reproductive tract which will affect future reproduction by that animal.
These are just a few of the concerns regarding egg retention. The important point is that egg binding is a serious medical condition and should be attended to immediately.
Editor's note (MJC): From my experiences of using oxytocin on tortoises and turtles, the time at which successful egg laying commences following the administration of the hormone can vary from 15 minutes to 2-4 hours. If you take an animal to a veterinarian who recommends oxytocin administration remember that the time to onset of egg laying can be quite rapid. Discuss this with the veterinarian. Take the oxytocin home and administer it yourself or leave the animal with the veterinarian. Either way avoids the risk of your animal laying her eggs in the back seat of your car on the way home!
What is oxytocin, and how does it work?
Oxytocin is a hormone produced from the posterior pituitary gland. It has many effects, ranging from stimulating the "milk ejection reflex", to transport of male sperm in the uterus, to simulating contraction of the smooth muscle of the uterus and thus inducing labor. Although few studies have been done using oxytocin in chelonians, there have been a number of reports documenting its efficiency in relieving egg binding.
In mammals, oxytocin is used to induce labor in pregnant females. In order for oxytocin to be effective many factors have to be just right. For instance, the uterus must be primed with the hormone estrogen before it can work. The hormones progesterone and epinephrine both inhibit the effects of oxytocin. If all of the variables are not just right the oxytocin will not stimulate egg laying.
It should be pointed out that if a female is egg bound there must be a reason for it. That is, it is not normal for an animal to retain its eggs. Treating it with oxytocin may resolve the symptom (egg retention) but it is not curing the problem. The fundamental cause of the egg retention must still be identified and corrected or the problem will persist. People with inadequate husbandry practices may find that they may have more than one female egg bound each season for that reason.
Improper use of oxytocin can result in death of the animal if the underlying problem is not identified and corrected. For instance, if oxytocin is given to an animal with existing pelvic damage and large eggs, the intense smooth muscle contraction may cause the gland to rupture internally, thus resulting in a serious life-threatening condition.
What are some other methods for removing eggs from an egg bound tortoise?
Warm water enemas, soaking the animal in a warm water bath, or placing the animal in a warm room will sometimes help stimulate an animal to deliver its eggs. If nutritional factors are a consideration, sometimes merely correcting the deficiencies will result in a cure. Often, it is a lack of calcium in the diet which causes reproductive failure. Administration of calcium either by injection or orally calcium and a warm environment may stimulate oviposition.
If enemas are tried, either simple warm water, or a sterile water soluble jelly should be used. Petroleum based jellies or lubricants can seal the pores on the eggs and kill them.
There have been reports of using a long hypodermic needle to pierce the eggs through the body wall in front of the rear legs. The idea is that it would allow the eggs to collapse to facilitate their passage through the pelvic canal. This will work, but there are disadvantages. Firstly, it destroys the eggs. Secondly, if any of the egg yolk leaks out into the body cavity there is the potential for egg yoke peritonitis. Thirdly, if the procedure is not performed in a sterile fashion the actual insertion of the needle may cause internal infection within the animal.
The best method for treating egg binding is to prevent it from happening. This is accomplished through a thorough understanding of the animal that you are working with, a sound knowledge of its nutritional needs and an awareness of the fundamental concepts of its reproductive biology.
Originally published in the Tortuga Gazette 30(5): 8-9, May 1994