Radiographic method for anatomic study of the teat canal: characteristics related to resistance to new intramammary infection during lactation and the early dry period.

An in vivo radiographic method to determine teat canal anatomy has shown that resistant quarters had teat canals with a smaller diameter than that of susceptible quarters. The length of the teat canal did not appear to be related to resistance to new intramammary infections. These findings relate to new infection caused by Aerobacter aerogenes, Streptococcus agalactiae, and Staphylococcus aureus. Quarters guarded by teat canals with larger diameter were less resistent to new infection during both lactation and the early dry period compared with quarters guarded by teat canals with small diameter.