Investigations on teat canal length in teats with milk flow disturbances

The objective of this study was to evaluate teat canal length as a test for ruptures in the teat canal area in teats with milk flow disturbances (Medl 's test). 144 dairy cows affected with covered milk flow disturbances in on e teat were used for this study. In affected teats the change in teat canal length was determined in comparison to the lateral neighbouring teat. The reasons of milk flow disturbances were diagnosed using endoscopy; they were categorized into ruptures in the area of the teat canal and other reasons (narrowing of the teat canal, free foreign bodies in the teat cistern). In teats with milk flow disturbances the teat canal was often lengthened. Unaf fected teat canal length and shortened teat canals were also observed. Leng thening of the teat canal by (2 mm may indicate ruptures in the teat canal area (79 % true positive results). When the teat canal was lengthened by (2 mm, however, other reasons may responsible for milk flow disturbances as w ell (47 % false positive results). Unaffected teat canal length may predict other reasons only to a limited extent (47 % true positive results). Howev er, when teat canal length is unaffected ruptures in the teat canal area ma y be excluded (7 % false positive results). We conclude, that Medl's test m ay be useful to differentiate between reasons of milk flow disturbances. Ho wever, teat endoscopy gives a more accurate diagnosis.