HEAD AND MOUTH SOUNDNESS ANATOMY OF THE MOUTH
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A sound mouth enables a sheep to grasp feedstuffs efficiently with minimal effort. A thin sheep can be the result of a very unsound or broken mouth. When lower incisors do not optimally meet with the dental pad, less feed can be consumed with each bite and possibly less feed consumed in total that results in body condition issues. A sound mature mouth will contain eight permanent incisors and twenty-four molars (six per side both top and bottom). Sheep have no upper incisor teeth, rather the lower incisor teeth align with the dental pad above them in order to allow the sheep to bite. A sheep’s incisor teeth develop with age, a new set each year for four years that replace the milk teeth, starting middle front and moving toward the molars. A lamb’s mouth will have only milk teeth. A yearling sheep will replace the middle pair of milk teeth with a set of adult incisors.
A two-year-old will replace the next pair and so forth for each additional year up to five years. Beyond four years the teeth will begin to show wear with age as all teeth are now permanent.
ENTROPION A genetic defect
observed in newborn lambs where the eyelid folds inward causing eye irritation. The lid should be rolled out to eliminate the abrasion. Sometimes it must be stitched open. Keeping notes on what animals or bloodlines within the flock produce lambs with this condition may help eliminate the problem due to its presumed genetic heritability. Treatment of sheep presenting entropion include applying manual eversion (gently pulling the eyelid back) or clipping the eyelid. BOTTLE JAW Bottle jaw is one sign that a sheep is severely infected with internal parasites (worms). The FAMACHA chart can also be used to determine severity of a worm infestation. Comparing the eye color to that in the chart will give an indication of severity. The color is the result of anemia in the sheep caused by the worm load. A fecal sample can be taken and analyzed for recommendations as to the proper wormer to use. Sheep with bottle jaw should be dewormed to address the particular parasite in question.
SOUND MOUTH The lower incisor teeth ideally meet the dental pad above. This alignment allows the sheep to bite and tear maximum mouthfuls of forage as it grazes. The upper and lower lips meet when the sheep is viewed in profile.
OVERBITE Lower incisors align behind the upper dental pad. Also known as parrot mouth or undershot jaw. Overbite is a genetic issue to avoid and a consideration for culling. It impairs the sheep’s ability to graze optimally, and this can result in a lower body condition score over time. Like a set of pincers the teeth and pad should meet to grasp and tear forage when grazing. The more severe this misalignment is the more problematic this issue can become.
UNDERBITE Lower incisor teeth extend forward past the dental pad. Also referred to as monkey mouth or over-shot jaw. Underbite is a genetic issue to avoid and a consideration for culling. It impairs the sheep’s ability to graze optimally, and this can result in a lower body condition score over time. Like a set of pincers, the teeth and pad should meet to grasp and tear forage when grazing. The more severe this misalignment is the more problematic this issue can become.
Illustrations by Cali Roberson
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