Prevalence of teat end hyperkeratosis in lactating dairy cattle and their association with animal variables
Abstract
Short and long -term changes in teat condition mainly caused by machine milking may affect the udder health of lactating dairy cattle. The objective was to investigate the prevalence of teat end hyperkeratosis scores in lactating dairy cattle in Germany and to determine associations between animal variables and teat end hyperkeratosis. The study was conducted in 15 German high -yielding dairy herds. On dairy farms teat size, teat shape, teat end shape and changes in teat condition (edema, t eat skin colour, teat end hyperkeratosis) were recorded. In total, 4,022 animals of the breed German Holstein were included into the present study. For both front and rear teats associations between teat end hyperkeratosis and lactation number, teat length , teat diameter and teat end shape were found. Further research is needed to reduce the prevalence of teat end hyperkeratosis in high -yielding dairy herds and to improve the teat condition.
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Introduction
Udder health problems cause huge economic loss in dairy milk production. Estimates put the amount of lost milk caused by raised somatic cell counts at 3 to 18% for cows with an average somatic cell count of 500,000 cells/ml [1]. Clinical mastitis is even more costly through discarded milk and treatment costs [2].
Poor teat condition is identified to be a risk factor for udder health problems in modern dairy herds. Authors categorize changes in teat end condition in three major groups: sho rt term, medium term, and long term changes in teat condition [3].
Short and medium term changes like congestion, edema, swelling of the teat base and petechia are clinical signs of an impaired circulation of blood and lymph. Teat end hyperkeratosis is a s o called long term change of the teat tissue [3]. In general, teat tissue changes are a result of mechanical stress affecting the tissue during machine milking [4]. Main risk factors for changes in teat condition are long machine -on times [4, 5, 6] , high v acuum levels [7, 8, 9] and overmilking [10, 11, 12].Additionally cow individual risk factors are described by several authors for extreme teat end hyperkeratosis. These factors are teat size [13] and teat end shape [14, 15] . Teat end hyperkeratosis may inf luence the prevalence of intramammary infections [16, 17] .
Mein et al. (2001) also tried to confirm thresholds for the interpretation of the teat end condition found in dairy herds [3].They recommend that less than 20 % animals have teats with teat end hyp erkeratosis exceeding the severity of a smooth white ring around the teat orifice.
The aim of this study was to describe the prevalence of teat end conformation traits including cow individual variables like teat size and teat end shape and milking induced teat tissue changes, especially teat end hyperkeratosis in high -yielding German dairy herds. Associations between cow individual variables and teat end hyperkeratosis were examined.
Conclusion
The development of hyperkeratosis has been described as a natural process of adaption to milking. There are some cow individual factors that influence their severity beside the mechanical forces of the milking process. These are especially te at end shape, teat length and diameter and lactation stage. Teat end condition was poor in the population involved in the present study and may affect udder health. The population examined in this survey was uniform regarding teat end shape and teat size. Breeding selection should continue to prefer animals without extreme teat sizes (too short as well as too long). Also pointed teat tips are not desirable .
