Estimating teat canal cross-sectional area to determine the effects of teat-end and mouthpiece chamber vacuum on teat congestion.

The primary objective of this experiment was to assess the effect of mouthpiece chamber vacuum on teat-end congestion. The secondary objective was to assess the interactive effects of mouthpiece chamber vacuum with teat-end vacuum and pulsation setting on teat-end congestion. The influence of system vacuum, pulsation settings, mouthpiece chamber vacuum, and teat-end vacuum on teat-end congestion were tested in a 2×2 factorial design. The low-risk conditions for teat-end congestion (TEL) were 40 kPa system vacuum (Vs) and 400-ms pulsation b-phase. The high-risk conditions for teat-end congestion (TEH) were 49 kPa Vs and 700-ms b-phase. The low-risk condition for teat-barrel congestion (TBL) was created by venting the liner mouthpiece chamber to atmosphere. In the high-risk condition for teat-barrel congestion (TBH) the mouthpiece chamber was connected to short milk tube vacuum. Eight cows (32 quarters) were used in the experiment conducted during 0400 h milkings. All cows received all treatments over the entire experimental period. Teatcups were removed after 150 s for all treatments to standardize the exposure period. Calculated teat canal cross-sectional area (CA) was used to assess congestion of teat tissue. The main effect of the teat-end treatment was a reduction in CA of 9.9% between TEL and TEH conditions, for both levels of teat-barrel congestion risk. The main effect of the teat-barrel treatment was remarkably similar, with a decrease of 9.7% in CA between TBL and TBH conditions for both levels of teat-end congestion risk. No interaction between treatments was detected, hence the main effects are additive. The most aggressive of the 4 treatment combinations (TEH plus TBH) had a CA estimate 20% smaller than for the most gentle treatment combination (TEL plus TBL). The conditions designed to impair circulation in the teat barrel also had a deleterious effect on circulation at the teat end. This experiment highlights the importance of elevated mouthpiece chamber vacuum on teat-end congestion and resultant decreases in CA.

Effect of an automated dipping and backflushing system on somatic cell counts.

Postmilking teat disinfection is an effective management practice to prevent transmission of contagious mastitis pathogens from cow to cow. With farms increasing in size and an increase in the number of rotary milking parlors, the need for automation of postmilking teat disinfection is mounting. Automated teat dipping and backflushing (ADB) systems have existed for some years, but their effect on udder health was never examined in a field study on commercial dairy farms. The objectives of this study were, therefore, to evaluate the effect of introducing an ADB system in a herd on (1) bulk milk somatic cell count (SCC), (2) individual cow SCC, and (3) the proportion of newly elevated SCC. Dairy herd improvement data were collected over a 30-mo period on 25 sets of 3 farms. Each set of 3 farms contained a farm that installed an ADB system, one that disinfected teats using dipping after milking, and one that sprayed teats after milking. Data were analyzed using linear mixed models. Bulk milk SCC on farms that sprayed or dipped before installing an ADB system were 16,000 and 30,000 cells/mL lower in the period 6 to 18 mo after installation, respectively, than on farms that continued spraying or dipping the teats after milking. In the same period after installing an ADB system, proportions of cows with elevated SCC were 4.3 and 1.2% lower, respectively, compared with spraying and with dipping. Similarly, proportions of cows that had newly elevated SCC were 1.5% lower and 0.3% higher, respectively, compared with farms that sprayed or dipped. Installing an ADB system had a beneficial effect on bulk milk SCC, individual cow SCC, and the proportion of newly elevated SCC. The effect was most prominent in the period 6 to 18 mo after installation of an ADB system.

Short communication: Effect of automatic postmilking teat disinfection and cluster flushing on the milking work routine.

The importance of a consistent and comprehensive milking routine as a critical component of any mastitis control program is well documented. However, as pressure on time increases, farmers are faced with 3 options: (1) adjust the milking routine to suit the time available, (2) undertake the task less thoroughly, or (3) examine which elements of the milking routine can be automated and substitute capital expenditure for labor. A study was undertaken on 5 farms in the United Kingdom in October and November 2007 to assess the effect on milking time of installing a commercial automatic postmilking teat disinfection and cluster back flushing system (ADF). Two of the farms recruited for the study were intending to purchase the ADF system in the near future and 3 farms had already invested in the technology. The farms ranged in size from 120 to 550 cows and included three 90° rapid exit parlors, a herringbone parlor, and an abreast parlor. All 5 farms were visited for 2 successive milkings before the ADF was installed or disabled, and a detailed time and motion analysis was undertaken. After ADF was installed or the system reactivated, a further 2 milkings were monitored. All monitored farms showed a measurable reduction in milking time after the ADF system was installed. However, the magnitude of the reduction was greater than would be expected by simply removing the elements of postmilking teat disinfection and cluster sanitization. The benefits of ADF are greater than simply disinfecting teats and back flushing clusters and the time saving obtained may allow a more structured milking routine that may have additional benefits in terms of mastitis prevention and control.

An evaluation of raw milk microorganisms as markers of on-farm hygiene practices related to milking.

Dairy farm hygiene audits were undertaken at 24 farms during summer and winter and the results compared with transformed bacterial indicator levels in raw milk samples collected during each audit. The bacterial indicators measured were total viable counts, Escherichia coli, coliforms, Bacillus spp., Bifidobacteria spp., and Pseudomonas spp. The results of initial comparisons using Pearson product-moment correlation coefficients showed presumptive relationships between some bacterial groups and the subjective quantitative audit scores. When investigated further using linear regression, the presumptive relationships were found to be influenced by external factors. Possible reasons for the low correlations between on-farm hygiene and bacterial indicator counts in raw milk were further investigated. Measurements of the uncertainty associated with the bacteriological results were undertaken and revealed geometric relative standard deviations that ranged from 0.019 to 1.05. Toward the higher end of this scale, the uncertainty associated with the laboratory estimations of bacterial numbers may have been large enough to blur hygiene score-marker bacteria relationships. The samples obtained from on-farm raw milk storage tanks were representative of the whole tank contents and not a significant source of error. Although total bacterial counts are widely acknowledged by the milk industry as not always giving a true measure of on-farm hygiene during milking, we were unable to find any marker bacteria that showed consistently higher correlations and were thus better suited as indicators of on-farm hygiene.

Evaluation of measurements of the conductivity of quarter milk samples for the early diagnosis of mastitis.

Measurements of the conductivity of quarter milk samples were made in 31 cows in a 70-cow herd in southeast England, for a period of 15 weeks. Over this period, 42 per cent of cow-weeks and 20 per cent of quarter-weeks had an increase in quarter milk conductivity of 10 per cent of more compared with the mean conductivity of the previous 14 milkings. Fourteen per cent of quarter-weeks had an increase in conductivity of 15 per cent or more. The geometric mean somatic cell count (cell count) was higher in quarter-weeks with a 10 per cent or greater increase in conductivity than in quarter-weeks with a conductivity change of less than 10 per cent. At a conductivity threshold of 10 or 15 per cent and a cell count threshold of 200,000 or 400,000 cells/ml the specificity of this system was estimated to be 85 to 92 per cent, the sensitivity 40 to 54 per cent, the negative predictive value 87 to 93 per cent and the positive predictive value 33 to 55 per cent. The positive predictive value of the individual quarter milk conductivity was insufficiently accurate to be used as the sole criterion for the selection of quarters for early antibiotic treatment.

Changes in cow teat tissue created by two types of milking cluster.

We have investigated the responses of cow teats to machine milking in a study of relatively newly installed commercial milking parlours fitted with one of two types of milking cluster. The first was a common type with a large claw volume (> 200 ml), 15-16 mm i.d. long milk tube, 10 mm short pulse tube, cluster weight < 3-2 kg and used alternate pulsation. The second was a more traditional type with a 150 ml claw bowl volume, 13.5 mm i.d. long milk tube, 8 mm short pulse tube, cluster weight approximately 3.5 kg and used simultaneous pulsation. We scored approximately 50 cows in each of 20 herds, all within 60 s of cluster removal, for changes from the premilking teat condition: teat colour (creation of reddening or blueness), firmness, thickening at the base of the teat associated with the position of the liner mouthpiece, and whether the teat duct orifice was open. There were statistically significant differences in the proportion of cows displaying these four alterations in teat condition between herds using the two types of cluster. The more common type of cluster was always associated with better teat condition. The cause and effect of poorer teat condition have not been fully established and are likely to be multifactorial. The principal risk factors may be cluster weight, overmilking, vacuum applied during the overmilking phase and the design of the liner mouthpiece.