Effect of ambient temperature and daylength on hoof growth in sheep

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Abstract
SUMMARY: In Southdown sheep, which grazed and were fed during the day to maintain body weight and were housed at night, there was no clear effect of ambient temperature on hoof growth. In these sheep, equatorial or reversed photoperiods did not influence hoof growth.In an indoor experiment over 19 months on Merino sheep, with natural light and temperature, fleece accumulated normally between spring shearings. Hoof growth in winter was low at a low level of nutrition but was not reduced in sheep at a higher nutritional level. It fell dramatically at both levels of nutrition in the first month after shearing.Hoof growth was measured in Merino and Southdown sheep exposed to equatorial daylength in two climate-room experiments in which ambient temperature was varied. Fleece length was kept short and nearly constant by clipping. Hoof growth was greatly reduced by low temperature. At a given ambient temperature it was more rapid when ambient temperature was rising from month to month than when it was falling. The low hoof growth observed in the cold was associated with low hoof temperature and there was some evidence suggestive of reduced blood flow to the skin of the lower legs.These temperature effects would complicate the use of hoof growth as an index of nutrition.