The objective was to measure teat canal length and diameter, teat diameter and teat wall thickness by ultrasonographic scanning in order to determine the differences in bovine breeds, and to study the influence of teat canal length and diameter on the occurrence of mastitis. A total of 269 lactating dairy cows of four different breeds (Brown Swiss, Simmental, Simmental crossbred with Red Pied, and Holstein-Friesians) from seven Upper Austrian dairy farms were examined. Average teat canal length of Brown Swiss animals was shortest (15.7 mm) followed by Holstein-Friesians (17.2 mm) and Simmental (18.3 mm). These differences in teat canal length were highly significant (P < or = 0.001). There was no significant difference in teat canal length between pure-bred and crossbred Simmentals. Differences of teat canal diameter between breeds were significant (P < or = 0.05). Brown Swiss animals had the largest diameters (2.0 mm) and Holstein-Friesians the smallest (1.7 mm). Differences in teat diameter between Brown Swiss, Holstein-Friesian and Simmental were also significant. No differences were found between the pure-bred and crossbred Simmental cows. The narrowest teats were in Holstein-Friesians and the widest in Simmental. Holstein-Friesians also exhibited the thinnest teat walls while the Simmental had the thickest ones. Teat canal length and diameter were correlated with udder health. Teat canals of healthy udders tended to be longer (17.4 mm) and narrower (1.8 mm) than teat canals of infected udders (15.8 mm, 2.1 mm; P < or = 0.001). A logistic regression model showed significant effects of teat canal length, teat canal diameter and lactation number on udder health.

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Mycoplasmas possess complex pathogenicity determinants that are largely unknown at the molecular level. Mycoplasma agalactiae serves as a useful model to study the molecular basis of mycoplasma pathogenicity. The generation and in vivo screening of a transposon mutant library of M. agalactiae were employed to unravel its host colonization factors. Tn4001mod mutants were sequenced using a novel sequencing method, and functionally heterogeneous pools containing 15 to 19 selected mutants were screened simultaneously through two successive cycles of sheep intramammary infections. A PCR-based negative selection method was employed to identify mutants that failed to colonize the udders and draining lymph nodes in the animals. A total of 14 different mutants found to be absent from >95% of samples were identified and subsequently verified via a second round of stringent confirmatory screening where 100% absence was considered attenuation. Using this criterion, seven mutants with insertions in genes MAG1050, MAG2540, MAG3390, uhpT, eutD, adhT, and MAG4460 were not recovered from any of the infected animals. Among the attenuated mutants, many contain disruptions in hypothetical genes, implying their previously unknown role in M. agalactiae pathogenicity. These data indicate the putative role of functionally different genes, including hypothetical ones, in the pathogenesis of M. agalactiae. Defining the precise functions of the identified genes is anticipated to increase our understanding of M. agalactiae infections and to develop successful intervention strategies against it.

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