1.1. Learning Objectives

• Be familiar with the reproductive disease conditions that commonly affect the production laying hen
• Understand the reasons for the development of egg-binding in pet birds and poultry and be able to recognize, diagnose and recommend treatment options for this condition in pet birds.
• Be familiar with the management options for chronic egg-laying in cockatiels

1.2. Review

Please review Reproductive Physiology notes on avian reproduction.

2.1. Estrogen osteomyelosclerosis

(Polyostotic hyperostosis)

This is a normal physiologic event that occurs in ovulating birds resulting in the formation of new bone within the medullary cavity of long bones. The new bone may fill the entire marrow cavity. This condition coincides with ovarian follicular maturation and the calcium stored in the new bone is used for egg-shell production. The reabsorption of this calcium occurs by osteolysis but the exact mechanism of induction is unknown. Cortical long bone is not resorbed during egg production in birds if dietary calcium is optimal.

3.1. Salpingitis

Salpingitis is usually seen as a sporadic problem in poultry flocks where Mycoplasma gallisepticum infection is present. Infections affecting the left greater abdominal air sac or the peritoneal cavity have potential for extension into the oviduct. It also occurs in pet birds, especially those with persistent egg laying problems. In many instances oviductal infections appear to originate from ascending cloacal infections. In the early stages of disease small erosions/ulcers and mucosal edema are present with or without fibrinopurulent exudate. Later the amount of exudate increases dramatically and ultimately the oviduct becomes distended with a mass of yellow or white caseous material.

It is also possible that some of the material in these oviducts represents impacted egg yolk components. Culture of the luminal contents of an impacted oviduct usually reveals a wide array of bacteria and even fungi.

The oviduct becomes non-functional early in the course of disease and the ovaries of affected hens are usually atrophied.

3.2. Impacted Oviduct

This condition is often seen in older hens and occasionally in pullets that come into production before there is complete body development and sometimes in extremely obese laying hens. The oviduct is impacted with a mass of broken shells, shell membranes, or aggregates of coagulated albumin and yolk. Eggs enclosed in shell membranes are sometimes found in the abdominal cavity. This obviously indicates that eggs were formed normally but then retropulsed back into the peritoneal cavity. Hens with many eggs within the abdominal cavity are said to walk with a penguin-like posture.

3.3. Chronic Egg Laying

Chronic egg laying is a common problem in several species of companion birds, especially the cockatiel. It is characterized by an individual hen laying repeated clutches, or continuing to lay beyond the normal clutch size, often without end! It occurs without the presence of a mate. Causes are likely hormonal and environmental, however attempts to manipulate environmental conditions often fail in controlling this problem. Consequences of chronic egg-laying are exhaustion, calcium depletion, egg-binding (see below), coelomitis, salpingitis, etc. Occasionally a bird will spontaneously stop laying, but will usually start up again with a prolonged egg-laying period in the following winter or spring.

Treatment for chronic egg-laying should include attempts to manipulate the environment: altering the photoperiod, removing nest sites, perceived mates, etc. Hormonal treatments have included medroxyprogesterone acetate (Depo-provera), levonorgestrel, HCG and most recently leuprolide acetate (Lupron) a synthetic analog of GnRH. Lupron has been the most effective and the safest therapy to date. To prevent seasonal recurrence and avoid repeated hormonal therapy surgical hysterectomy is recommended as a permanent cure. This surgical procedure can be quite risky.

3.4. Egg binding

Egg binding in pet birds is most often a result of hypocalcemia resulting from either a nutritional deficiency or protracted egg-laying and an excessive drain of calcium for egg shell production. The lack of available calcium during the laying process results in primary uterine inertia and the birds inability to contract and expel the egg.

Other causes include chronic egg-laying, vitamin A deficiency, environmental stresses, poor physical condition on the hen, young hen (first clutch), large egg, or an anatomical abnormality. There may also be a genetic predisposition for egg-binding. This condition is most commonly seen in budgies, cockatiels, and finches, but can be seen in any female laying bird.

3.5. Oviductal Prolapse

Prolapse or eversion of the terminal oviduct can occur to a high degree in some laying flocks. In the process of oviposition, there is a normal eversion of the uterus as the egg is delivered. In poorly developed, obese birds the everted mucosa may be slow to retract. In there is any tendency towards cannibalism in the flock, cage or pen mates will peck at the everted mucosa causing trauma and edema which further slows or prevents retraction. Continued irritation may promote further straining and overt prolapse of the oviduct.

The lesion can range from a barely perceptible eversion of the cloaca which protrudes from the vent to an elongated segment of the oviduct which protrudes for several centimeters.

Some of the most common causes for this condition are:

• Young, poorly developed pullets just coming into production.
• Flocks with higher than recommended population densities.
• Increased obesity
• Flocks that are poorly de-beaked
• Persistent egglaying in pet birds (cockatiels)

Cloacal prolapse in a cockatoo

4.1. Readings