Disorders of Reproductive Systems

Cystic Right Oviduct

Fluid accumulation in the vestigial right oviduct is a common finding in hens. The abdominal cyst is filled with clear fluid and is attached to the right side of the cloacal wall. The cyst may vary in size from barely perceptible to 15-20 cm in diameter. An increased incidence has been observed in flocks after infectious bronchitis virus outbreaks. Oviductal cysts are a necropsy finding that rarely, if ever, affect flock performance.

Defective or Abnormal Eggs

Most “ridged,” “sunburst,” “slab-sided,” soft-shelled, or double-shelled eggs are the result of eggs colliding in the shell gland when an ovum (yolk) is released too soon after the previous one. Necropsy examinations have demonstrated that 2 full-sized eggs can be found in the shell gland pouch. As the second egg comes in contact with the first, pressure is exerted, disrupting the pattern of mineralization. The first egg acquires a white band and chalky appearance, while the second egg is flattened on its contiguous surface (ie, slab-sided). Pimpled or rough eggs may have been retained too long in the shell gland. Blood spots result when a follicle vessel along the stigma ruptures as the ovum is being released. Meat spots occur when a piece of follicle membrane or residual albumen from the previous day is incorporated into the developing egg.

Many abnormalities occur as “accidents” (no specific cause), but the incidence is much higher in hens subjected to stressful management conditions, rough handling, or vaccination during production. A significant increase in the number of soft-shelled eggs is also common as a result of viral disease such as infectious bronchitis, egg drop syndrome, and exotic Newcastle disease.

Small eggs with no yolk form around a nidus of material (residual albumen) in the magnum of the oviduct. Small eggs with reduced albumen and eggs with defective shells may be the result of damage to the epithelium of the magnum or shell gland.

Very rarely, foreign material that enters the oviduct through the vagina (eg, a roundworm) may be incorporated into an egg.

Egg-bound or Impacted Oviducts

A fully formed egg may get stuck in the shell gland or vagina because the egg is too big (eg, double-yolked) or because of hypocalcaemia, calcium tetany, or previous trauma (pecking) to the vent and/or vagina. This condition may be more prevalent in pullets that start production before body development is sufficient or in hens that are extremely obese. It occurs more often during spring and summer months due to over-stimulation of birds by increasing light intensity and day length. When impaction occurs, eggs that continue to form create layers of albumen and yolk material, and the oviduct becomes very large. Some eggs are refluxed to the abdominal cavity, and affected hens assume a penguin-like posture.

Egg Peritonitis
(Egg yolk peritonitis)

Egg peritonitis is characterized by fibrin or albumen-like material with a cooked appearance among the abdominal viscera. It is a common cause of sporadic death in layers, but in some flocks may become the major cause of death and give the appearance of a contagious disease. It is diagnosed at necropsy. Peritonitis follows reverse movement of albumen and Escherichia coli bacteria from the oviduct into the abdomen. If the incidence is high, culture should be done to differentiate between Pasteurella (fowl cholera) or Salmonella infection.

When hens have too many large ovarian follicles, a problem described as erratic oviposition and defective egg syndrome (EODES) is seen in broiler breeders. This condition is accompanied by a high incidence of double-yolked eggs, prolapses of the oviduct, internal ovulation, and/or internal laying that often results in egg peritonitis and mortality. EODES is prevented by avoiding light stimulation of underweight pullets too early and following body weight and lighting recommendations for each breeder strain. Overweight hens may also have a higher incidence of erratic ovulations and mortality associated with egg peritonitis.

False Layer

These hens ovulate normally, but the yolk is dropped into the abdominal cavity rather than being collected by the oviduct because of obstruction of the oviduct after infection with E coli or Mycoplasma gallisepticum . The yolk is absorbed from the abdominal cavity. The hen looks like a normal layer but does not produce eggs. Hypoplasia of the ovary and oviduct has been associated with infectious bronchitis virus infections (Infectious Bronchitis) at an early age (1-2 wk). Atresia or even atrophy of the ovary are caused by severe stress, chronic infections, and feed refusal due to mycotoxins in the feed.

Hypocalcemia, Sudden Death, Osteoporosis, or Cage Layer Fatigue

Pullets or hens with insufficient dietary calcium, phosphorus, or vitamin D3 may die suddenly or be found paralyzed from hypocalcemia while shelling an egg. This may be associated with high production and withdrawal of calcium from bones for egg shell production, in which case the main lesion may be osteoporosis. At necropsy, there is an egg in the shell gland and the ova are not regressed. There are no other lesions, although medullary bone may be lacking. Paralyzed hens respond to calcium IV, and this response may be useful in diagnosis.

Hens with osteoporosis may show similar signs at necropsy, or the ova may be regressing with no egg in the oviduct. The femur is always fragile, and medullary bone is always absent in osteoporosis. These hens may also respond to calcium IV if there are no fractures of the legs or vertebrae. Osteoporosis is a major cause of death in high-production flocks. The use of large particle size calcium (limestone, oyster shell) in the diet may be beneficial. High rates of mortality due to fractures are common in birds affected with osteoporosis. This situation is more common in birds in wood-slatted houses due to the trauma caused by jumping on and off the slats. Ruptured egg follicles indicating trauma can be found during necropsy examination of these birds.

In recent years, a condition known as hypocalcemia or calcium tetany (paralysis) has been seen in high-yielding broiler breeders. Careful postmortem examination reveals a fully active ovary and the presence of a partially or fully formed egg in the shell gland in the absence of other lesions. This indicates that the hen used all available calcium from the bloodstream in an effort to complete the egg shell. The condition is common in flocks with poor body weight uniformity that are fed high-calcium diets in the weeks prior to the onset of lay and brought into production by drastic increases in day length and feed allocation. Hypocalcemia can be prevented by management practices that promote body weight uniformity and avoid excessive/premature allocation of high-calcium diets and light stimulation. Mortality can be reduced by the administration (“topping of the feed”) of 5 g of oyster shell per hen for 3 consecutive days, and addition of vitamin D3 to the drinking water. This treatment should be suspended for 3 days and then repeated. Severe cases will require continual treatment for 2-3 wk (3 days of treatment, followed by 3 days without).

Mortality and the presence of an egg in the shell gland also can be caused by a condition referred as to sudden death syndrome, first reported in Australia. This is believed to be caused by marginal levels of potassium and phosphorus in the diet, resulting in cardiomyopathy.

Internal Layer

In these hens, partially or fully formed eggs are found in the abdominal cavity. Such eggs reach the cavity by reverse peristalsis of the oviduct. If they have no shell, they are often misshapen due to partial or complete absorption of the contents. Frequently, only empty shell membranes are present. No control or treatment is known. This condition is related to erratic ovulation and defective eggs (see Defective or Abnormal Eggs).

Infertility

Because males may have a harem of females that they defend from other males, infertility is more important in the male than in females. However, obese females may be less efficient in transporting sperm to the infundibulum resulting in reduced fertilization of the ovum as it is released from the ovary. The male must be dominant to the females or mating will not occur. Commercial turkey hens are inseminated artificially with semen collected from the stags and used the same day. (See artificial insemination, Artificial Insemination: Introduction). Parthenogenesis is responsible for some infertility in turkeys. There are host sperm glands in the oviduct of females, and live sperm can be retained for 3-4 wk. Waterfowl have a rudimentary penis, and prolapse of the penis is occasionally reported in drakes. There is no treatment.

Neoplasia

The most frequent tumor of the reproductive system is carcinoma of the oviduct. Neoplastic cells are shed from tumors in the oviduct into the abdominal cavity. They implant on the ovary, pancreas, and other viscera and produce multiple, hard, yellow nodules. They may block lymph return and result in ascites. The incidence increases with age, and this tumor may be a frequent cause of death after 2 yr. Affected hens are condemned at processing.

Leiomyoma of the broad ligament is an estrogen-induced hypertrophy of the smooth muscle of the broad ligament. It is benign and is an incidental finding at necropsy or processing.

A variety of ovarian and testicular tumors has been described. Marek’s disease (Newcastle Disease) is also found frequently in the ovary.

Oophoritis and Ovary Regression

Regression of the ovary may result in leakage of free yolk into the abdomen (yolk peritonitis); this rarely causes death except when yolk material migrates through the air sacs to the lung and causes foreign body pneumonia. Free yolk occurs in many cases of acute illness, injury, or forced molt. Regression of the ovary is frequently caused by low body weight, deliberate reduction of feed, overcrowding, or lack of feeder space. Infectious diseases such as exotic Newcastle disease, fowl cholera, pullorum disease, and avian influenza are known to cause this condition. It can also result from severe stress, which is often accompanied by feather molt, emaciation, and dehydration.

Prolapse of the Oviduct

When an egg is laid, the vagina everts through the cloaca to deliver the egg. If there has been injury to the vagina, such as from a large egg, or if the hen is fat, the vagina may not retract immediately. This may result in cannibalism ( Cannibalism). When the protruding organ is pecked by others in the flock, the complete oviduct and parts of the adjacent intestinal tract may be pulled from the abdominal cavity (“peckout”). Alternatively, the vagina swells, cannot retract, and remains prolapsed (“blowout”). The hen dies from shock. A high incidence has been associated with excessive/premature photostimulation, early laying (inadequate body size), large eggs, double-yolked eggs, and obesity. Cannibalism may be prevented by beak trimming, maintaining appropriate stocking density, and avoiding nutritional deficiencies.

Salpingitis

Salpingitis is an inflammation of the oviduct, which may contain liquid or caseous exudate. In young pullets, it is often due to Mycoplasma gallisepticum , E coli , Salmonella spp , or Pasteurella multocida (fowl cholera) infection and can result in reduced egg production. It is a frequent lesion in female broilers and ducks at processing. On gross examination, salpingitis may be difficult to differentiate from impacted oviduct in adults. As the oviduct becomes nonfunctional, the ovaries are usually atrophied. Unless associated with an infectious problem, this condition tends to be found sporadically during necropsy of cull hens.

Sex Reversal

If the normal left ovary of a hen is destroyed by infection, the vestigial right organ may develop as a testicle and the hen may develop male characteristics. Neoplasia in the adrenal glands or ovary that result in the production of testosterone could also cause the development of male secondary sexual characteristics (comb and wattles) in affected females.
Reference :- Merck Veterinary Manual
 
Web Site Designed by SAG IT Solutions
Copyright © 2009-2012 Regenbiocorps. All rights reserved.