CHAPTER 25: UPPER GASTROINTESTINAL TRACT DISORDERS
Introduction The upper gastrointestinal tract is considered to include the oral cavity, the teeth, the tongue, the salivary glands, the esophagus and the stomach. Abnormalities in the oral cavity or in dentition prohibit the normal ingestion, mastication and deglutition of food. They may also impair the horse’s ability to work with a bit in its mouth. Dysfunction or obstruction of the esophagus prevents the movement of food from the oral cavity to the stomach.
Dysfunction of the stomach prevents the chemical digestion of food from occurring normally.
Dental Disorders
Brachynathism Brachynathism is a congenital conformational abnormality that is commonly called “ ______________”. Brachynathism is an inheritable genetic trait and is seen to run in families. Horses with brachynathism have an abnormally short ______________ , while the maxilla and incisive bones are of normal length, which causes abnormal occlusion of the incisors. In extreme cases the upper and lower incisors may have no contact whatsoever. This causes difficulty in the prehension, ingestion and mastication of food, and causes abnormal wear of the incisors.
Brachynathism is the most common dental anomaly and is usually mild enough to be considered a conformational flaw rather than a pathology.
Brachynathism is best viewed form the ______________ , and is seen as the length of the upper jaw exceeding that of the lower jaw. If the lips are retracted it is visible that the upper incisors are positioned rostral to the lower incisors, and that there is abnormal occlusion of the incisors. Depending on the severity of the abnormality the horse may have difficulty ____________ , and may be unable to tear the grass blades with its incisors. In severe cases foals have difficulty suckling from their mothers, or may be unable to suckle, and mature horses may not be able to eat well from a bucket. Difficulty gaining weight and quidding are indications that the animal is having difficulty eating. Over time the abnormal occlusion of the teeth will change the function of the ______________ leading to temporomandibular joint dysfunction. Therefore, some horses with brachynathism may be reluctant to be bridled or may be resistant to bit pressure. The structure of the hard palate may also change over time in horses whose incisors do not contact.
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