From the Merk Veterinary Manual (@good2016 )
"Star-gazing" is the "wry neck"
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"Star-gazing" is the "wry neck"
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Thiamine deficiency is most common when poorly processed fish meals are used, because they contain thiaminase enzyme. In such situations, adding extra thiamine may be ineffective. There is no good evidence suggesting that, unlike in some mammalian species, certain Fusarium mycotoxins can increase the need for supplemental thiamine. In otherwise adequate diets, deficiency is prevented by supplements of thiamine up to 4 mg/kg.Polyneuritis may be seen in mature birds ~3 wk after they are fed a thiamine-deficient diet. As the deficiency progresses, birds may sit on flexed legs and draw back their heads in a star-gazing position. Retraction of the head is due to paralysis of the anterior neck muscles. Soon after this stage, chickens lose the ability to stand or sit upright and topple to the floor, where they may lie with heads still retracted. Thiamine deficiency may also lead to a decrease in body temperature and respiratory rate. Testicular degeneration may be noted, and the heart may show slight atrophy. Birds consuming a thiamine-deficient diet soon show severe anorexia. They lose all interest in feed and will not resume eating unless given thiamine. If a severe deficiency has developed, thiamine must be force-fed or injected to induce the chickens to resume eating.
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