Influence of milk flow rate and streak canal length on new intramammary infection in dairy cows

Abstract

Eighteen cows with a wide range of quarter peak flow rates (O35-2-22 kg/min) were inoculated with Streptococcus agalactiae and Str. dysgalactiae 4 mm into each streak canal every 3 d for 12 d. Thirty of the 72 quarters developed intramammary infection. Mean peak flow rate and length of streak canal of those quarters that became infected were 1-26 + 0-08 kg/min (mean + SEM) and 11-47±0-41 mm respectively, compared with 101 + 0 0 5 kg/min and 1205±035 mm for those that remained uninfected. Logistic regression analysis showed that the probability of infection increased significantly with the increase in peak flow rate (P = 0-01). The influence of streak canal length on new infection, after allowing for the effect of peak flow rate, was not significant at the 5 % level (P = 0'07), suggesting that there may be an inverse relationship between teat duct length and infection, but that it is of secondary importance to peak flow rate. If increased mass of milk distends the teat duct by raising intramammary pressure, then quarter susceptibility to infection is further compromised. These results strongly suggest that the benefits of reduced infection from mastitis control, achieved despite dramatic increases in milk flow rate and milk yield, are significantly underestimated. Some attention has been paid in the past to the relationship between teat patency, measured as ease of milking, and the incidence of intramammary disease. Little (1937) emphasized the importance of an intact teat duct sphincter as a barrier to invasion and suggested that sphincters of older cows are less efficient, rendering such cows more susceptible to infection. Dodd & Neave (1951) identified a significant relationship between fast flow and new intramammary infection. Recently Grindal & Hillerton (1991) confirmed these findings and identified the enhanced risk from mastitis of pulsationless milking and impaction of milk droplets on the teat end to fast flow rate quarters. McDonald (1971), in a histological study, showed a marked difference in the cross section between streak canals from susceptible and resistant glands. The teat canals from the susceptible quarters had a larger diameter and thinner stratum corneum than the canals from resistant quarters. Hibbitt et al. (1969) identified the antibacterial properties of keratin and emphasized its importance in the defence of the mammary gland. This supported the observations of Murphy (1959), who showed that partial removal of the keratin by a reaming process produced a temporary decrease in resistance of the canal to invading pathogens.

Ultrasonographic measurement of the bovine teat: breed differences, and the significance of the measurements for udder health

“…Mean values of the parameters are different from those reported earlier (McDonald, 1968a ;Grindal et al 1991;Hamana et al 1994) especially in the longer teat canal. These outcomes are explained by the use of different kinds of methods and mechanical manipulation of the teats to be examined.…”

“…Natural defence mechanisms against udder pathogens are the teat and teat connective tissue. The influence of teat canal length and diameter on the occurrence of mastitis by bacterial pathogens has been examined (McDonald, 1975;Grindal et al 1991;Scherzer, 1992;Seyfried, 1992;Hamana et al 1994 ;Lacy-Hulbert & Hillerton, 1995). Grindal et al (1991) could find no significant influence of teat canal length on new infection McDonald (1975) and Hamana et al (1994) but, additionally, they found significant differences in teat canal diameter between healthy and infected udder quarters.…”

“…The influence of teat canal length and diameter on the occurrence of mastitis by bacterial pathogens has been examined (McDonald, 1975;Grindal et al 1991;Scherzer, 1992;Seyfried, 1992;Hamana et al 1994 ;Lacy-Hulbert & Hillerton, 1995). Grindal et al (1991) could find no significant influence of teat canal length on new infection McDonald (1975) and Hamana et al (1994) but, additionally, they found significant differences in teat canal diameter between healthy and infected udder quarters. Scherzer (1992) postulated that length of teat canal is not associated with acute mastitis, but that a relatively longer teat canal gives rise to more udder pathogens and may be related to chronic or subclinical mastitis.…”

Relationship between California Mastitis Test score and ultrasonographic teat measurements in dairy cows

“…One study showed that CL was longer (1.74 cm) in healthy udders than in infected udders (1.58 cm), and that CL and the number of lactations were related to the CMT score of the cows 10 . Others reported the CL as 1.14 ± 0.41 cm in infected teats and 1.20 ± 0.35 cm in non‐infected teats, 20 and Gulyas and Ivancsics found a positive correlation between CL and somatic cell count 28…”

“…Other advantages of ultrasonography for evaluating intramammary tissues are its ease of use and being non‐invasive 8,12,16–18 . Ultrasonographic techniques can be used to determine the intramammary factors that may lead to the development of mastitis and these factors should be taken into consideration in the control and prevention of mastitis 13,16,19–22 …”