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.

Development of protocols to evaluate in-line mastitis-detection systems.

This paper proposes and discusses a methodology to evaluate the performance of automated mastitis-detection systems with respect to their practical value on farm. The protocols are based on 3 on-farm requirements: (1) to detect cows with clinical mastitis promptly and accurately to enable timely and appropriate treatment, (2) to identify cows with high somatic cell count to manage bulk milk SCC levels, and (3) to report the mastitis infection status of cows at the end of lactation to support decisions on individual cow dry-cow therapy. Separate protocols for each requirement are proposed and discussed, including gold standards, evaluation tests, performance indicators, and performance targets. Aspects that require further research or clarification are identified. Actual field data are used as examples. Further debate is invited, the aim being to achieve international agreement on how to evaluate and report performance of different mastitis-detection technologies. Better performance information will allow farmers to compare different mastitis-detection systems sensibly and fairly before investing. Also, the use of evaluation protocols should help technology providers to refine current, or develop new, automated mastitis-detection systems. Such developments are likely to accelerate adoption of these systems, potentially leading to improved animal health, milk quality, and labor productivity.

An automated in-line clinical mastitis detection system using measurement of conductivity from foremilk of individual udder quarters.

AIM: To assess a novel method for automatic in-line detection of clinical mastitis. METHODS: For a brief period at the start of milking for each cow, electrical conductivity of foremilk was measured for each quarter in turn, using a single sensor installed in the long milk tube (LMT) about 1.5 m downstream from the milking-machine claw. Sequential separation of flow between udder quarters was achieved by control of pulsation to individual teat cups within a conventional cluster. The ratio of conductivity values between quarters was used as an indicator of mastitis status. The concept was evaluated initially in a pilot trial in a 200-cow herd milked in a 23-stall swing-over herringbone milking parlour. It was then tested rigorously in a field trial in a 640-cow herd milked in a 50-stall rotary milking parlour. Both trials were conducted in the Waikato region of New Zealand. In the latter trial, sensor results were compared with visual inspection of a commercial in-line mastitis filter fitted to each milking unit. These filters were inspected for clots immediately after every cow's milking, for 3 weeks. The dataset of approximately 27,000 individual milkings was tested against several published or potential alternative 'gold standards' for diagnosing clinical mastitis. RESULTS: In the pilot trial, 12-14 clinical events were detected out of 19 true clinical quarters, with a false-alert rate of between three and five false electrical-conductivity alerts per 1,000 individual milkings. In the more rigorous field trial, sensitivity ranged from 68 to 88%, and the false-alert rate (false-alert episodes per 1,000 individual milkings) ranged from 2.3 to 7.0. CONCLUSION: The novel clinical mastitis detection system, based on separation of the flow and measurement of electrical conductivity from foremilk of individual udder quarters, has the potential to provide a new tool for helping farmers to monitor clinical mastitis in herds milked with conventional clusters.

Automatic detection of clinical mastitis is improved by in-line monitoring of somatic cell count.

This study explored the potential value of in-line composite somatic cell count (ISCC) sensing as a sole criterion or in combination with quarter-based electrical conductivity (EC) of milk, for automatic detection of clinical mastitis (CM) during automatic milking. Data generated from a New Zealand research herd of about 200 cows milked by 2 automatic milking systems during the 2006-2007 milking season included EC, ISCC, monthly laboratory-determined SCC, and observed cases of CM that were treated with antibiotics. Milk samples for ISCC and laboratory-determined SCC were taken sequentially at the end of a cow milking. Both samples were derived from a composite cow milking obtained from the bottom of the milk receiver. Different time windows were defined in which true-positive, false-negative, and false-positive alerts were determined. Quarters suspected of having CM were visually checked and, if CM was confirmed, sampled for bacteriological culturing and treated with an antibiotic treatment. These treated quarters were considered as gold-standard positives for comparing CM detection models. Alert thresholds were adjusted to achieve a sensitivity of 80% in 3 detection models: using ISCC alone, EC alone, or a combination of these. The success rate (also known as the positive predictive value) and the false alert rate (number of false-positive alerts per 1,000 cow milkings) were used to evaluate detection performance. Normalized ISCC estimates were highly correlated with normalized laboratory-determined SCC measurements (r = 0.82) for SCC measurements >200 x 10(3) cells/mL. Using EC alone as a detection tool resulted in a range of 6.9 to 11.0% for success rate, and a range of 4.7 to 7.8 for the false alert rate. Values for the ISCC model were better than the model using EC alone with 12.7 to 15.6% for the success rate and 2.9 to 3.7 for the false alert rate. Combining sensor information to detect CM, by using a fuzzy logic algorithm, produced a 2- to 3-fold increase in the success rate (range 21.9 to 32.0%) and a 2- to 3-fold decrease in the false alert rate (range 1.2 to 2.1) compared with the models using ISCC or EC alone. Results suggest that the performance of a CM detection system improved when ISCC information was added to a detection model using EC information.

Is retirement good or bad for mental and physical health functioning? Whitehall II longitudinal study of civil servants.

BACKGROUND: To determine whether retirement at age 60 is associated with improvement or deterioration in mental and physical health, when analysed by occupational grade and gender. METHODS: Longitudinal study of civil servants aged 54 to 59 years at baseline, comparing changes in SF-36 health functioning in retired (n=392) and working (n=618) participants at follow up. Data were collected from self completed questionnaires. RESULTS: Mental health functioning deteriorated among those who continued to work, but improved among the retired. However, improvements in mental health were restricted to those in higher employment grades. Physical functioning declined in both working and retired civil servants. CONCLUSION: The study found that retirement at age 60 had no effects on physical health functioning and, if anything, was associated with an improvement in mental health, particularly among high socioeconomic status groups.

Predictors of early retirement in British civil servants.

BACKGROUND: it is uncertain how recent changes in labour force dynamics may have influenced the increasing numbers of people taking early retirement in industrialized countries. The Whitehall II study provides an opportunity to examine the predictors of early retirement in one of the largest employers in the United Kingdom. METHODS: we examined the factors predicting early retirement in a 7-year follow-up period from 1988 to 1995 using longitudinal data on 2532 male and female London-based civil servants aged between 50 and 59.5 years. Baseline data on employment grade and duration of time working for the Civil Service were obtained from self-completed questionnaires. The primary factors examined included health, work characteristics, questions about job demands and job satisfaction and financial insecurity, wealth and material problems. Time until early retirement was analysed using Cox proportional hazards model. RESULTS: of the 2532 civil servants, 26.7% retired early during the follow-up period. We found that men and women in the higher-paid employment grades, those that had suffered from ill health and those that were less satisfied with their jobs were more likely to retire early, whereas material problems tended to keep people working. CONCLUSIONS: our results show that self-perceived health, employment grade and job satisfaction are all independent predictors of early retirement. Qualitative analyses may further advance our understanding of the retirement process.

Paradigms of retirement: the importance of health and ageing in the Whitehall II study.

This paper evaluates four well established sociological theories of ageing using qualitative data from the British Whitehall II study. We attempt to apply the theories to contemporary retirement and through each theory examine the issue of health in retirement. The effect of lowered income in retirement is discussed in relation to Townsend's theory of structured dependency. Change in participant's health following retirement is examined in respect of the theory of disengagement by Cumming and Henry, adjustment to retirement in relation to Laslett's theory of the third age. Parson's role theory is used to examine how social interactions and relationships change for people who have recently retired. We discuss the need for a multifaceted theory of ageing which can accommodate the continually changing experience and age of retirement. We analysed interviews conducted with 25 male and female civil servants aged between 55 and 63 years, from different grades who had been retired for less than 2 years.

Teat thickness changes may provide biological test for effective pulsation.

Pulsation rates of 40, 60 and 80 cycles/min were combined with pulsator ratios of 50, 60, 70 or 80 percent in two experiments with different liners. Machine-induced, short-term changes in teat thickness of 14 cows were compared with milk flow rate characteristics and machine strip yields to evaluate the effectiveness of pulsation in relation to liner type. Post-milking teat thickness increased progressively as the b phase of the pulsation cycle was lengthened, and as the d phase was shortened, at all pulsator rates and with either liner. Teat thickness values increased significantly (P < 005) when the d phase was < 15%. For ratios of 50 and 60% , teat thickness decreased progressively as pulsation rate was increased. At the higher ratios, thickness values were lowest at 60 cycles/min. Pulsation settings that tended to increase teat thickness values also increased both peak milk flow rates and machine strip yields. The influence of liner type on teat thickness changes appeared to be at least as important as the influence of pulsator ratios and greater than the effect of pulsation rate. If so, then international standards for acceptable pulsation characteristics cannot be defined solely in terms of pulsator settings. A limit of +/- 5 percent for machine-induced changes in thickness of the teat apex would be an additional guideline for effectiveness of pulsation in relation to both liner type and vacuum level. This could provide a basis for a dynamic test applied to milking cows under field conditions.

Strategies for mastitis control: dry cow therapy and culling.

The effects of three selection strategies for dry cow therapy on prevention of new infections and rate of antibiotic usage were compared. Quarter infection status of 1044 cows in 12 herds was determined by bacteriological methods at drying off, calving and three to five months into the following lactation. Cows that were uninfected at drying off were randomly allocated to treatment (whole udder, dry cow therapy) and non-treatment groups. Infected cows were randomly allocated to whole udder or infected quarter only treatments. The strategies compared were blanket treatment (treat all quarters of all cows), selective cow treatment (treat all quarters of any cow infected in one or more quarters) and selective quarter treatment (treat infected quarters only). Selective cow treatment was identified as the preferred strategy. Blanket treatment resulted in increased antibiotic usage (15.5 vs 6.4 tubes per infection eliminated) with no additional benefit, and selective quarter treatment resulted in a higher new infection rate (6.4% vs 3.9% quarters) in the dry period. The prevalence of infection within a herd at drying off had no influence on new infection rates in the dry period or early lactation. The cure rate after dry cow treatment (mean of 66%) decreased significantly with increasing age (P < 0.001). Cows infected in the previous lactation contributed over 76% of infections at calving and nearly 70% at mid-lactation. To lower the incidence of mastitis in a herd, a greater emphasis on culling of older infected cows and prevention of new infections during lactation is needed.

Influence of pulsationless milking on teat canal keratin and mastitis.

Twenty-four Holstein cows, producing at least 21 kg of milk/d, were used in two replicate experiments to determine the effect of presence or absence of pulsation on loss of teat canal keratin during machine milking. Left quarters were milked without pulsation and right quarters were milked with pulsation. On d 0 and 10, keratin was collected from one left and from one right teat canal of each cow prior to milking and from the remaining two teat canals after milking. Milk was collected for assessment of SCC and bacteriological status on d 0 and approximately every 3 d until d 18. Quantity of keratin recovered before milking on d 10 did not differ between teats milked with or without pulsation, but loss of keratin because of milking was greater from teats milked with pulsation. By d 7, 30% (12 of 43) of quarters milked without pulsation had become infected, but no (0 of 47) quarters milked with pulsation were infected. By d 14 to 16, new infections had increased to 68% (28 of 41) of quarters milked without pulsation and 2% (1 of 43) in quarters milked with pulsation; mean SCC in pulsationless quarters increased sevenfold relative to pulsation quarters. Protein and water content of keratin did not differ because of treatment, and changes in lipid composition were minor. Histological analysis of the teats of 4 cows indicated that the mean diameter of the teat canal, within 2 h after milking, was greater without pulsation than with pulsation (680 vs. 483 microns).

Milking the 30,000-pound herd.

The principles for milking the 13,600-kg (30,000-lb) cow are the same as for any other dairy cow: she should be milked gently, quickly, and completely with minimal machine stripping or over-milking. The application of these principles may differ, however, because high producing cows have 1) lower premilking stimulus requirements than low producers, 2) higher peak milking rates and higher average flow rates (yet longer times to milkout), 3) higher incidence of teat orifice lesions such as hyperkeratosis, and 4) higher risk of new mastitis infections. Existing national and international standards for construction and performance of milking systems may not be adequate to manage the higher expected flow rates through the milking unit and milklines. Such standards need to be reviewed and perhaps revised to ensure appropriate sizing and flow characteristics based on sound engineering principles and physiological requirements. Milking four times per day increases daily milk production compared with twice per day, and milking eight times per day increased daily production compared with four times per day. Cows milked more than four times per day might not require complete milking out at every milking. More frequent milking (or milking on demand) may be achieved with robot milkers, provided that robots can match the reliability of human milkers.

Teat tissue reactions to milking: effects of vacuum level.

Machine-induced changes in diameter, thickness, and compressibility of the teat apex and teat barrel were measured on all teats of four cows milked at vacuums of 25, 30, 40, and 50 kPa. Measurements were made with an electronic caliper instrument immediately before milking and then at .5, 15, and 30 min after milking. Teat length was also measured at these times. Immediately after milking, for the two higher levels, teats were significantly thicker (7 to 10% thicker at 40 kPa, 17 to 25% at 50 kPa), shorter (by 3 to 6 mm), smaller in diameter (by 2 to 4 mm for the apex, 3 to 6 mm for the barrel), and less compressible for all milking treatments compared with the premilking status for individual teats. Although teat thickness recovered to the premilking mean values 30 min after milking at 40 or 50 kPa, the barrel still was significantly thicker after 30 min compared with those at the lower vacuum treatments. We suggest that changes in teat length, diameter, thickness, and compressibility after milking at low vacuum levels mainly reflect tissue responses to udder evacuation. In contrast, increased teat wall thickness and reduced compressibility of teat tissue at higher vacuum levels likely result mainly from machine-induced edema.

Simplified quantitative estimation in vitro of lymphocyte radiosensitivity applied to patients with chronic lymphocytic leukaemia.

Lymphocyte survival changes observed at 1, 2 and 3 days as responses to 3 doses of ionising radiation in vitro (40, 100, and 500 cGy) are analysed by computer according to a simple (single cell population) mathematical model. Intrinsic radiosensitivity, the susceptibility to lethal injury, which is expressed as the D37 value (the radiation dose permitting 37% survival), is estimated separately from the kinetics of subsequent death of lethally-irradiated cells (expressed as their half-life, or t1/2 value). Among the 35 patients with B-cell CLL studied (15 were never treated), both parameters varied widely and independently of one another. t1/2 ranged from 9-200 h and above, D37 from 14-500 cGy or above. Twenty-three patients were deemed 'radiosensitive' (D37 below 110 cGy). D37 level did not correlate with treatment status, mode of treatment, clinical staging (Rai) or lymphocyte count. With some exceptions, D37 remained relatively constant for individual patients with increasing duration of disease or alterations in treatment status. The assay method may prove useful as an aid in predicting response to low-dose splenic irradiation (SI) in CLL.

Effects of antibiotic therapy at drying off on mastitis in the dry period and early lactation.

Four strategies for selecting cows for intramammary therapy with benzathine cloxacillin at drying off were compared in 12 Victorian dairy herds. The bacteriological status of all quarters of all (1044) cows was determined just before drying off, within 2 d of calving, and again 3 to 5 months after calving. All cases of clinical mastitis (from calving to mid-lactation) were recorded. Cows not infected at drying off were allocated randomly to 2 subgroups of approximately 350 cows each: not infected, not treated (NI-NT), or not infected, all quarters treated (NI-AT). New infection rates in the dry period (3.8% for NI-NT vs 2.1% for NI-AT) and in early lactation (4.1% for NI-NT vs 3.9% for NI-AT) were low and these differences were not significant. Incidence of clinical mastitis in early lactation was almost 50% higher for the treated group of uninfected cows compared with the untreated group (0.05 less than p less than 0.1). Cows infected in one or more quarters at drying off were split randomly into 2 subgroups of approximately 170 cows each: infected, all quarters treated (I-AT), or infected quarters treated only (I-QT). The new infection rate during the dry period was nearly 4 times higher for I-QT (15.3%) due to significantly more new infections by Staphylococcus aureus and Streptococcus uberis.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of machine-induced changes in thickness of the bovine teat.

Machine milking induced repeatable, short-term changes in thickness of the teat apex. These changes were measured with a spring-loaded caliper instrument under milking conditions that imposed differing forces on the teat apex. The mean percentage changes in teat end thickness (relative to the premilking values for individual teats) varied from 10% decrease up to 20% or more increase depending on the particular milking system used. The overall decrease in teat end thickness associated with cannula milking, milking at very low vacuum levels or milking with positive pressure pulsation may result from: (i) decrease in the intramammary pressure; and/or (ii) small changes in tone of teat musculature; and/or (iii) changes in the distribution of interstitial fluids in the teat apex. The overall increase in teat thickness caused by conventional or PKME milking systems results mainly from oedema (the extravascular accumulation of fluid). It is likely that milking equipment can, and should, be designed to minimize circulatory impairment resulting in oedema of the teat.

Closing forces of the bovine teat canal.

The magnitude of the forces causing closure of the bovine teat canal was estimated by measuring the pressure required to cause retrograde flow of milk into the canal from a manometer attached to the external teat orifice. Before milking, the hydrostatic pressure required to cause retrograde flow was 12 kPa or greater. Retrograde flow occurred at a pressure of 4-6 kPa once the teat canal surface had been wetted. This 2- or 3-fold fall in the closing forces presumably resulted from the combined effects of fracturing the teat canal epithelium and loss of initial resting tension in the smooth muscle fibres surrounding the teat canal. After milking, retrograde flow into any teat canal occurred at a pressure approximately 1 kPa lower than the wetted, pre-milking value. This small drop, and subsequent recovery approximately 30 min after milking, reflects the change in tonicity of the smooth muscle fibres which are stretched during milking. At hydrostatic pressures below 7-9 kPa, retrograde flow could be arrested momentarily by the occurrence of a teat contraction. At 4-7 kPa, the wave of contraction was also capable of expelling 4-14 microliters milk from the teat canal indicating the outwardly directed, peristaltic nature of the phasic muscular activity.

Compressive load applied by the teatcup liner to the bovine teat.

The magnitude of the cyclic load applied to the teat apex by the collapsed liner during milking was estimated by measuring the pressure required to cause retrograde flow of milk into the teat canal from a manometer attached to the external teat orifice. The study was extended by observation of the milk flow cycle within a transparent teatcup assembly and by pressure recordings within the teat canal using a catheter-tip transducer. The source of the force compressing the teat is the small airspace, within the collapsed liner, directly below the teat apex. The total force generated is determined mainly by the size of this airspace and the pressure difference (PD) acting across the opposing liner walls. When the PD reached 80-90% of the liner vacuum, the load was just sufficient to occlude the teat canal. Further increase in PD provided the compressive load capable of offsetting vascular congestion of the teat apex. Increasing liner tension increased the load applied. The narrow range of compressive loads applied by conventional liners (5-12 kPa above atmospheric pressure) may be sufficient to offset congestion and oedema in the teat. Loads greater than the mean arterial pressure within the teat apex might serve only to expose the tissues to non-productive compression.