Korean Journal of
Veterinary Service

In birds, natural, healthy regurgitation and forceful, violent vomiting is at first unable to spot the difference because all birds have a natural, gentle form of food expulsion that mirrors how a bird would feed its mates and offspring in the wild. Birds’ regurgitation is of no cause for concern. Vomiting in birds, however, is worrisome, and could be a sign of something more serious (Tully Jr, 2018). It is a violent, messy sight, and discharge may wind up spattered around the cage and on the bird. Such a forceful ejection of material or food may indicate an infection, liver or kidney disease or possibly, a serious condition called a “blocked gizzard”. A blocked gizzard is a life-threatening condition that requires immediate veterinary care and treatment. With fast treatment, birds may overcome this dangerous condition. If the condition is prolonged, however, the outcome is typically poor. A blocked gizzard (the second chamber of the stomach) in birds is a life-threatening condition that occurs when a buildup of materials or a foreign body becomes lodged in the gizzard (Reissig and Robles, 2001; Han et al, 2009).

Symptoms of blocked gizzard in birds include vomiting, increased thirst, fluffed-up appearance, loss of appetite, and depression. Stomach ache causes the bird to lean forward on the perch, and droppings are clear and/or white due to no fecal component. Finally, those birds die.

A blocked gizzard may be caused when a bird consumes a foreign object, such as a piece of wire, rope fiber, a particle from a toy, paper, among others (Schlegel and Brash, 2015). Birds may chew on such objects due to playful behavior, inquisitiveness, boredom, or sexual frustration. The bird may also be seeking to fill a mineral deficiency, assuage hunger, avoid contaminated food or equalize any dietary irregularities (Samour, 2015). For some reason, wet weather sends many birds in search of soil, potting soil, sand, or any kind of gritty substances. They will scavenge for these materials in excess, which may cause a blockage in the gizzard. Otherwise, a blocked gizzard may be part of a larger health problem. If untreated, the blockage may become more cumbersome and take on a “cement” consistency, causing the bird pain and in many cases, death (Huang et al, 2019).

To understand the gizzard of a bird requires a basic understanding of avian anatomy. Birds have two-part stomachs. The first part, the proventriculus, receives the undigested food, and begins to break it down by producing acid. Once the food is partially broken down, it moves into the second stomach chamber, the gizzard. The gizzard is a muscular organ that plays a significant role in the bird’s digestive system (King and McLelland, 1984; Fowler, 1991; Samour et al, 2015). Appropriately nicknamed the “gastric mill”, the organ acts by grinding and crushing food in order to enable the next step in the digestive process (Allardyce and Linton, 2010). The gizzard can grind the food with previously swallowed stones and pass it back to the true stomach, and vice versa. In layman’s terms, the gizzard chews the food for the bird because it does not have teeth to chew food the way humans and other mammals do (Ni et al, 2018). The gizzard retains a certain amount of grit and tiny stones that help to grind and pulverize hard food, and also smooth rough particles for safe passage through the intestines (De Francisco et al, 2003; Dunislawska et al, 2022). This case reports that in its simplest terms, a blocked gizzard stopped the digestive process, and impacts the bird leading perforation of duodenum resulting in peritonitis to death.

An adult female yellow-billed spoonbill (Platalea leucorodia) weighing 1.5 kg was found dead while being maintained at the zoo. At necropsy, no specific external findings were observed in gross pathology. However, after dissection, the abdominal cavity showed symptoms of jaundice (Fig. 1), the liver was yellow and slightly enlarged, being suspected as a fatty liver (Fig. 1). In the gastrointestinal tract examination, perforation was observed in the stomach and the descending duodenum, and fish spines that looked like loaches were tightly embedded in the gastric mucosa (Fig. 2). A pseudomembrane was formed over the entire stomach due to severe gastritis. Fish spines were accumulated and stored up to the duodenum, and this mass obstructed the intestinal tract and caused perforation, resulting in peritonitis.

Figure 1. (A) Abdominal cavity with symptoms of jaundice, (B) Yellowish, enlarged liver. Yellow-billed Spoonbill (Platalea leucorodia).

Figure 2. (A) Perforation of the stomach and descending duodenum, (B) Fish spines tightly embedded in the gastric mucosa, (C) After removal of the gastric membrane in which the fish spines were embedded, (D) Fish spines in duodenal perforation. Yellow-billed Spoonbill (Platalea leucorodia).

Gizzard impaction is usually known as a particular problem associated with ranging chickens (Christensen, 1998). This is caused by long grass, or other material such as plastic bags, becoming coiled into a plug in the gizzard (Schlegel and Brash, 2015). Christensen (1998) describes how long ropes of twisted grass of up to 6 cm in length resulted in mortality rates of up to 1% per week in free-range hens. On post-mortem, these ropes of grass were found extending into the duodenum from the gizzard.

Crop impaction can also occur, and is more often the result of problems lower down in the gastrointestinal tract that have created a gizzard malfunction (Samour, 2015). When birds ingest food such as fish, it is stored in the crop, which empties completely overnight, mechanically shredded in the gizzard, digested by enzymes in the proventriculus, the true stomach, and then the digested food is sent to the duodenum (Huang et al, 2019). However, in our case, undigested sharp fish bones were lodged in the gastric mucosa and clumped together, blocking the lumen. Thereafter, the intestinal wall was perforated and peritonitis occurred causing death. The exact cause of the fish spines becoming lodged in the gastrointestinal tract is unknown. However, it can only be assumed that there was a lack of a mechanism to go around and pick up grit or small stones and assist in mechanical crushing in the gizzard.

The provision of grit can significantly aid the functioning of the gizzard. Although most free-ranging hens will pick up small stones and grit, the provision of a supplementary source will be required for birds that are reluctant rangers, or in situations where the soil is lacking stones. Our bird was kept in a zoo and spent most of time on cement floors with no opportunity to pick up small rocks or other hard materials (Christensen, 1998; Huang et al, 2019). It is highly likely that these breeding conditions were not suitable for the normal digestive process of the bird to occur: the toothless bird species swallowed food such as fish with its beak, stored it for a while in the crop, mixed with hard materials such as pre-swallowed stones in the gizzard, ground with muscle force, and then moves to the proventriculus to meet digestive enzymes (Allardyce et al, 2015).

There is little veterinary guidance on the treatment of impaction of poultry. One report said that treatment with 3 g of Epsom salts per 100 birds per day plus 10∼15 ml of liquid molasses per bird fed as a wet mash for four days. Further energy and lubrication can be provided by the addition of vegetable oil (Christensen, 1998). However, this method is obviously a way to ensure that the grass plug produced by ingesting long grass in poultry can easily pass through the gastrointestinal tract, and it far from the treatment applicable to wild birds that consume fish or small amphibian reptiles with bones. Grit might be one of options to help prevent impactions for those birds, although grit has been found to aid only in the breakdown of grass that is already in small or marrow pieces. Natural grit may not be beneficial to help break down consumed materials and not easy for zoo birds to find. Rough in texture and small to have the highest surface area to volume ratio and must be supplemented in enough quantity to allow for an adequate grit to food ratio in the gizzard (Huang et al, 2019). At least for wild birds maintained in zoos, prevention should be prioritized over treatment, so it seems that further consideration should be given to the breeding condition in the future.

This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through Animal Disease Management Technology Advancement Support Program, funded by Ministry of Agriculture, Food and Rural Affairs (MAFRA) (Project No. 122013-2).

No potential conflict of interest relevant to this article was reported.