Teresa L. Lightfoot D.V.M., Diplomate ABVP - Avian
Chronic egg laying is defined as the laying of eggs in excess of what would be normal for a particular species, or the production of a number of eggs that is detrimental to the health of the hen.
Species most prone to chronic egg-laying in the pet bird population include cockatiels, lovebirds, budgies, and some Aratinga sp. (small/medium conures). These species also seem to be the most prone to excessive egg laying without the presence of a mate.
When a relatively healthy hen is presented for chronic egg laying, it is critical to collect a thorough history including a thorough discussion the environment. The presence or absence of conspecific (especially males), sexual or bonding behavior with the owner or inanimate objects, the presence in the cage of nest boxes or locations that the bird considers nesting areas, and the light/dark cycle must all be addressed before a remedy is attempted. Often the changing of environment and light cycle are sufficient to (at least temporarily) stop the ovulation.
Light cycle regulation entails reducing the daylight to only 8 to 10 hours per day initially. This is often difficult for owners to achieve, leaving them only an hour or less with their bird after work prior to putting the bird "to bed". Also the mere covering of their cage unless moved to a dark, quiet room, does not deceive many birds. If they overhear the normal family routine, they are generally wide awake under their blanket, and their hormonal axis does not receive the necessary signals that it is no longer the season for breeding. These birds must be moved to a dark and quiet area of the house. Reassure the owners that the limited daylight and isolation are temporary measures. After three weeks, most of these birds can be brought back out to enjoy the family's normal schedule for a period of four to six weeks. Observant owners will begin to recognize the signs of broodiness or increased sexual activity and can return the bird to the decreased day length when they observe these signs.
The use of exogenous hormones to manipulate the bird's sexual status has been used successfully for many years. The standard treatment with long acting progesterone, (medroxyprogesterone acetate, Depo-Provera, Upjohn Co., Kalamazoo, MI, at 5 - 25 mg/kg IM) was used in the late 1970's through the early 1990's. Although this drug was successful in halting egg-laying, it has many potential side effects. Minimally, hens treated with this drug will generally gain weight, develop some degree of polydipsia and polyuria (PU/PD) and may become lethargic, sleeping for extended periods of time. The susceptibility of any individual bird to side effects is unpredictable, and the same dose that in one bird will only produce a temporary moderate weight gain and PU/PD, could cause the next bird to develop severe hepatopathy, diabetes mellitus, and even death. Currently, this drug is seldom used for these reasons. Occasionally in a bird with severe and repeated egg-binding episodes that are potentially life threatening, the risk of a Depo-Provera injection may be warranted. The owner must be warned of potential side effects. The lowest possible dose should be used, and preliminary serum chemistries, including bile acids, should be conducted. Subsequent weight checks should be done, and the owner should be questioned as to the severity of side effects noted at home. Attempts to environmentally manipulate the bird to avoid the need to repeat this injection should be incorporated into the treatment protocol.
The more recent use of human chorionic gonadotropin (hCG, Pregnyl, Organon, Inc., West Orange, NJ, USA) to stop chronic egg-laying has met with good success in many circumstances. This hormone has primarily luteinizing hormone (LH) alpha sub-unit activity. LH causes an increase in progesterone (and some increase of estrogen and testosterone) in female birds. The fact that hCG increases the endogenous production and release of progesterone would seem contraindicated in egg-laying, since progesterone is present at high levels during ovulation. However, the level of progesterone, and its distribution and reception by the developing follicles, is critical to their continued development. Excessive progesterone supplied to the smaller ovarian follicles (whether directly by progesterone, or indirectly by LH administration) causes atresia of these developing follicles. Therefore, a typical sequence with the administration of hCG is that the hen will often lay one or even two more eggs, before an extended quiescent period is achieved. The dosages that have been used, and the dosage protocols are all empirical. A fairly standard and effective regimen is to administer 500 - 1,000 units/kg of hCG upon presentation of the chronic egg-layer, repeating this dose on day three and day seven. Generally, several months will elapse prior to a recurrence of egg-laying. Once again, every attempt should be made to manipulate the environment to prevent the recurrence of egg-laying. Although to date, hCG appears extremely safe (as noted by serial serum chemistries, weight checks, and lack of clinical problems following repeated administration), the efficacy of this drug may diminish over time. This is proposed to be due to the development of antibodies to hCG. This phenomenon of resistance to the hCG, requiring more frequent and higher doses, is most often noted when it is used for feather plucking, since the frequency of administration in generally higher when this syndrome is being treated.
One notable situation where this regimen tends to either fail, or be successful for a much shorter interval, is with a female cockatiel in the presence of a male cockatiel ("presence" being defined as either in the same cage, same room, or within calling distance). The owner should be cautioned that all the environmental and chemical manipulation available might not be sufficient to overcome the natural hormonal response to the male. If the owner is unwilling to separate the male from the female, then the environmental and hormonal treatments may decrease the frequency of egg-laying, but generally will not prevent it altogether. In these cases, serum chemistries, a complete blood count, and radiographs should be taken to determine whether the bird is maintaining homeostasis with the increased demands of frequent egg production. Supplemental calcium should be supplied, such as oral calcium glubionate (Neo-Calglucon , Sandoz Pharmaceuticals, East Hanover, NY) at 1.0 ml/kg BID, a calcium enriched antacid (Tums ), or judicious use of a calcium/Vitamin D3 powder, such as Osteoform. A total dietary percentage of 0.3% for egg-laying birds is generally sufficient to prevent calcium deficiency. Note that many formulated diet labels contain only 0.05% calcium. Cuttlebones are often provided by the owner as a source of calcium, when in actuality the birds generally use these for chewing and beak sharpening, not ingestion.
The GnRh agonist, Depo-Lupron12 functions to increase in release of LH and FSH. Its efficacy is probably also based on the bird's response to LH, either by the initial production of progesterone or the subsequent negative feedback and decreased production of sex hormones. The role of FSH in birds in not well understood. The disadvantage to this medication is that it is extremely expensive. The advantage is that there may not be antibody production to GnRh. In this author's experience, birds that have responded to hCG initially and subsequently develop a tolerance (antibodies?) to this medication, often respond to Depo-LupronR. Birds that have not responded to hCG to date have not responded to Depo-LupronR. Administration of hCG and Depo-Lupron simultaneously may have a pharmokinetic basis (producing an initial increase in progesterone that causes follicular atresia and subsequent negative feedback from Depo-Lupron stimulating multiple sex hormones, thereby halting ovulation. This has empirically worked well in a clinical setting, and conforms with the principles as outlined by Nico Shomaker in his thesis on GnRh agonists (personal communication, January, 2001).
Allowing a female cockatiel to incubate a clutch may provide a method to decrease total egg production. Cockatiels, being determinate layers, will often stop laying when they "feel" a full clutch under them as they brood. Some practitioners have reported being able to decrease the number of eggs in a clutch by adding artificial eggs under the hen after she has laid the first egg, creating a total perceived clutch size of five to six eggs. Some females will still continue to lay eggs, often up to 10 or 12 in sequence. The danger of hypocalcemia causing soft-shelled eggs and uterine inertia and potential for ectopic ovulation with subsequent peritonitis, rises with the number of eggs laid.
There is no single answer to excessive egg production. Client education and compliance, and ensuring the health and proper nutrition of the hen, can reduce the frequency and/or severity of the problem, giving the hen the maximum quality of life under the prevailing circumstances.
Egg bound birds
If the bird presents with rear end paresis or paralysis, thin, markedly depressed or with labored respiration, your prognosis must be guarded. Be sure to provide supportive care before attempting extraction of the egg. Hydrate the bird with fluids, give injectable calcium, and warmth. Some veterinarians elect to give an injection of a short acting glucocorticoid (for potential renal and cloacal swelling as well as shock ) and an antibiotic for potential sepsis. An ideal drug for inducing oviposition, if one emerges, is yet to be determined. Oxytocin and the avian equivalent, arginine vasotocin both cause uterine contractions. The prostaglandins, f2 alpha prostaglandin, (Lutalyse , dinoprost tromethamine, Upjohn , Kalamazoo, Michigan) prostaglandin E2 (Prostin E2 suppository, dinoprostone, Upjohn, Kalamazoo, Michigan, may also be administered for inducing egg laying. If the egg is adherent to the uterine wall or unable to descend (often due to soft tissue swelling or collection of urates and stool), the administration of any of these drugs could theoretically lead to uterine rupture. However, these medications, especially oxytocin and the prostaglandins that are available to the average practitioner, have been administered by experienced avian veterinarians successfully for many years. If the egg doesn't pass with early medical management, I prefer to use Isofluorane and manual extraction. In my hands, the decreased stress (due to decreased pain) and increased muscle relaxation warrant the slight anesthetic risk. Monitor respiration continuously - it WILL be labored if the bird is kept sufficiently light. The head should be held elevated to aid respiration. Barring adherence of the egg to the uterus, the administration of steady, unchanging digital pressure between the end of the sternum and the egg will cause the slow descent of the egg. At this point, the uterus will often evert, (don't let this alarm you) and then gradually reveal the white pinhole where the uterine opening is located. This opening will gradually dilate. Very seldom will any additional pressure or manipulation need to be done. The entire procedure generally takes less than two minutes under Isofluorane. After the egg is delivered, the uterus gradually "sucks" itself back up into position. A small amount of antibiotic/cortisone ointment in the vent (Panalog on a Q-tip) - seems to aid in reducing swelling, and allowing the bird to pass normal stool and urine more quickly. If any hemorrhage has occurred, and it often will as the uterus overstretches, antibiotics are definitely indicated to prevent cloacal and or uterine infection. Post-operatively the hen will continue to be depressed and have some labored breathing for a period of minutes to hours. Generally, by the next day, she has returned to normal, barring any complications (including a second egg - so don't forget to palpate her again, and warn the owner of that possibility).
References and Recommended Reading
1) Joyner, KL, Theriogenology. In Ritchie BW, Harrison GJ, Harrison LR (eds). Avian Medicine: Principles and Application. Lake Worth, FL, USA, Wingers Publishing Inc., 1994: 772-776.
2) Rosskopf WJ, Psittacine Conditions and Syndromes. Proc Annu Conf Assoc Avian Vet 1990: 432-450.
3) Speer BL, Diseases of the Urogenital System. In Altman RB, Clubb, SL Dorrestein, GM, and Quesenberry K (eds.) Avian Medicine and Surgery, WB Saunders, 1997: p 635 - 636.
4) Lightfoot, T. Clinical Use and Preliminary Data of Chorionic Gonadotropin Administration in Psittacines. Proc Annu Conf Assoc Avian Vet . 1996: p 303-307.
5) Sturkie PD. Avian Physiology. (fourth edition). Springer-Verlag, New York, NY, USA, 1988, p 415 - 416.
6) Plumb DC, Veterinary Drug Handbook (second edition). Iowa State University Press, Ames, Iowa, USA, 1995: 130 - 131.
7) Rosenthal K, Diagnosis in the Feather Picking Pet Bird, Proc of the N. Amer. Vet. Conf., 1996; p 741.
8) Cooper JE, Harrison GJ, in Avian Medicine: Principles and Application, Ritchie BW, Harrison GJ, Harrison LR, (eds), Wingers Publishing, Lake Worth, FL USA, 1994; 607-639.
9) Oglesbee BL, in Avian Medicine and Surgery, Altman RB, Clubb SL, Dorrestein GM, Quesenberry K, (eds) W. B. Saunders, Philadelphia, PA, USA, 1997; p 229 - 230.
10) Wilson L, Proc of the AAV Annual Conf, 1996; p 3 - 9.
11) Carpenter JW, Mashima TY, Rupiper DJ, Exotic Animal Formulary, Greystone Publications, Manhattan, KS, USA, 1996; p 130 - 141.
12) Lightfoot TL, hCG Preliminary Studies, Proc of the AAV Annu Conf, 1996; 303-306.
13) Van Sant F, Proc of Annu Conf of AAV, 1997; 383-391.
14) Ritchie BW, Avian Viruses: Function and Control.
References for Computer Wizards
1) Zen Publishing on CD for both IBM and the Mac is the Exotic Medical Library. Contains ALL the material in three major texts: 1) The monolithic work: Avian Medicine: Principles and Application, (Ritchie, Harrison & Harrison) 2) Avian Viruses: Function and Control, (Ritchie, BW) and 3) The Exotic Companion Medicine Handbook (Johnson- Delaney, C), with the ability to search all three at once for any given subject!! It is a great C/D reference.
2) Veterinary Information Network (VIN) - Nowhere have I found the scope and volume of interaction in veterinary medicine that is available through this service. You can "consult" with experts each day, and have answers the next. The exchanges with colleagues are often just as rewarding, especially when you have a "gee whiz" case. The academicians may not have seen it, but someone else out there may. Textbooks are necessary for in depth reviews, but to keep pace with the wealth of new information, VIN on-line can't be beat!