Increased Susceptibility to lntramammary Infection Following Removal of Teat Canal Keratin

Abstract

Influence of teat canal keratin on susceptibility to intramammary infection was investigated in lactating Jersey cows. In each of two replicate trials, keratin was removed from the left teats of 20 cows immediately before milking. Immediately after milking, all teats were exposed to bacterial challenge by immersion in a suspension of Streptococcus agalactiae (5 x 10(7) cfu/ml). Bacterial challenge was repeated after the next four milkings. Foremilk samples were obtained for 8 d after keratin removal to determine infection status. A mammary quarter was classified as infected based solely upon the bacteriological criteria outlined by the National Mastitis Council. The rate of infection in quarters from which keratin was removed was greater than that in control quarters. Infection rates were 26.3% for keratin-removed quarters and 8.3% for control quarters in trial 1 and 13.5 and 0%, respectively, in trial 2. When more stringent criteria (recovery of greater than 100 cfu of S. agalactiae/ml in three or more successive milk samples and a SCC of greater than 10(6)) were used to identify a subset of infections that were clearly intramammary, infection rates were 9.3% for keratin-removed quarters and 1.4% for control quarters. Thus, partial removal of keratin from the teat canal compromised the ability of the teat to prevent passage of bacterial pathogens from the external environment into the mammary gland.

The effects of inoculation of Mannheimia haemolytica into the teat of lactating ewes

“…In cows, the teat provides important protection for the mammary gland [29]. The keratin of the teat duct inhibits proximal progression of bacteria [6,17,33], subsequent cellular and humoral defence mechanisms occur in the teat cistern, e.g. leucocytes and non-specific antibacterial proteins [1,8,9,28,[30][31][32].…”

Immunohistochemical localization of adhesion molecules (CD62 and CD18) in the mammary gland of dairy cows

“…The teat canal is lined with keratin, which is crucial for the maintenance of the barrier function of the teat end. The removal of keratin was correlated with increased susceptibility to bacterial invasion and colonization (Capuco et al, 1992). 3.17 ± 24.96 34.97 ± 4.50 *P < 0.001 lower from CD18 and CD62L in parenchyma and Fürstenberg's rosette; P < 0.001 lower from CD18 in the central teat transverse section **P < 0.001 lower from CD18 and CD62L in parenchyma and Fürstenberg's rosette ***P < 0.05 lower from CD18 Fürstenberg's rosette and parenchyma…”

Melhoramento genético visando à resistência a mastite em bovinos leiteiros

“…Além disso, as proteí-nas catiônicas tem um efeito inibidor contra alguns agentes patogênicos como S. aureus e S. agalactiae (Hibbitt e Benians, 1971), semelhante à de proteínas que foram isoladas a partir de neutrófilos bovinos (Gennaro et al, 1983). No entanto, a eficácia antimicrobiana de queratina é limitada (Capuco et al, 1992), apesar da forte proteção física e química no canal do teto, existem várias maneiras pelas quais as bactérias podem penetrar no mesmo e causar infecção, por exemplo, a terapia incorreta de infusão intramamária ou por falhas de regulagem da ordenhadeira (Nickerson, 1990). Durante a ordenha, é comum que a queratina seja lavada com distensão do canal do teto (Garcia-Penarrubia, 1989).…”

“…Além disso, durante a ordenha mecânica, os microrganismos presentes na extremidade do teto são impelidos para a cisterna através do ducto do teto. Este mecanismo é considerado o principal mecanismo de propagação de agentes patogênicos da mastite contagiosa (Capuco et al, 1992;Sordillo et al, 1997). Fatores que afetam a integridade da camada de queratina podem, portanto, afetar a suscetibilidade à mastite.…”