Bulk Milk Cell Count Research Articles

Logistic regression model reveals major factors associated with total bacteria and somatic cell counts in goat bulk milk

Abstract The objective of this study was to identify on-farm risk factors associated with microbiological traits and somatic cell counts of goat bulk milk. A cross-sectional study was carried out on 160 goat dairy herds. Bulk tank milk samples were collected aseptically for qualitative (Salmonella enterica) and quantitative (aerobic mesophilic bacteria, total coliforms, E. coli, Staphylococcus spp. and Staphylococcus aureus) microbiological analyses. Additionally, information on various herd characteristics, general management practices, and milking procedures was collected by means of a questionnaire. A model for risk factors associated with the investigated traits was built by means of logistic regression after selection of putative variables by univariable analysis. Absence of pre-dipping, non-discharge of foremilk before milking and confirmed mastitis cases in the herds were identified as major risk factors for high aerobic plate counts. Low milk yield ( 7 years), the use of ponds as water source, long lactation periods (> 210 days), practice of milking in late pregnancy and non-discharge of foremilk before milking were also identified as risk factors for high SCC. The information generated by this study can support intervention measures targeting the improvement of goat milk quality, which is of paramount importance for the continuous development of the goat dairy industry.

The impact of genetic and non-genetic factors on somatic cell count as a monitor of udder health in Slovak Simmental dairy cows

Received: 2018-05-18 | Accepted: 2018-05-22 | Available online: 2018-11-26 https://doi.org/10.15414/afz.2018.21.04.166-168 The aim of study was to evaluate the impact of genetic and non-genetic factors on somatic cells count in Slovak Simmental dairy cows in period 2009 to 2013. We observed subsequent results in dairy cows of 55 822 Slovak Simmental cattle. Data were analysed using the SAS and linear model with fixed effects of herd, years and months controls, sire, breeding type. The results of somatic cells count during the years 2009 and 2013 were as follows: the highest number of samples was analysed during 2010 (n = 288 215), where the average count was 560.48*10 3 · ml -1 . The lowest average value of somatic cells count was of amount of 535.93*10 3 · ml -1 (n = 280 732) in 2009.The linear model represents coefficient determination R 2 = 0.038296 % (P<0.001) for SCC with all fixed effects. According to the analyses by the effects on SCC the highest effect was the effect of herd R 2 = 0.021625, then effect of sire R 2 = 0.015075. These effects were highly statistically significant (P<0.001). Correlation coefficients among milk in kg, fat, protein in % with somatic cells count were r = -0.12918, r = 0.04166 and r = 0.11423. These coefficients were highly statistically significant (P<0.001). Keywords: dairy cows, milk production, Slovak Simmental cattle, somatic cells count and coefficient of determination References Alhussien M.N., Dang A.K. (2018) Milk somatic cells, factors influencing their release, future prospects, and practical utility in dairy animals: An overview. Veterinary World, 11 (5), 562-577. DOI: https://dx.doi.org/10.14202/vetworld.2018.562-577 Boro, P., Naha, B., Prakash, Ch., Madkar, A., Kumar, N., Kumari, A., Prakash Channa, G. (2016) Genetic and non-genetic factors affecting milk composition in dairy cows. International Journal of Advanced Biological Research, 6 (2), 170-174. Ceron-Munoz, M., Tonhati, H., Duarte, J., Oliveira, J., Munoz-Berrocal, M., Jurado-Gamez, H. (2002) Factors affecting somatic cell counts and their relations with milk and milk constituent yield in buffaloes. Journal of dairy science, 85 (11), 2885-2889 https://www.journalofdairyscience.org/article/S0022-0302(02)74376-2/pdf de Freitas, J. A., da Silva, J., FroesGarcezNeto, A., Machado dos Santos, T. (2017) Somatic cell count and milk yield on physicochemical components of milk from free-stall housed cows. Semina: CienciasAgrarias, 38 (2). DOI: https://dx.doi.org/10.5433/1679-0359.2017v38n2p909 Jadhav, P.V., Tarate, S.B., Bhuvana, M., Das, D.N., Shome, B.R. (2016) Somatic cell count as a monitoring system for hygienic milk production in India: A review. Asian J. Dairy & Food Res., 35, 270-277. Japertienė, R., Anskienė, L., Japertas, S. (2016) Evaluation of the milk production and somatic cell count of Lithuanian purebred and crossbred dairy cows. VeterinarijairZootechnika, 73 (95) Supplement, 51-57. Jattawa, D., Koonawootrittriron, S., Elzo, M. A., Suwanasopee, T. (2012) Somatic cells count and its genetic association with milk yield in dairy cattle raised under Thai tropical environmental conditions. Asian-Australasian journal of animal sciences, 25 (9), 1216. DOI: https://dx.doi.org/10.5713/ajas.2012.12159 Oudah, E. Z. M. (2009) Non-genetic factors affecting somatic cell count, milk urea content, test-day milk yield and milk protein percent in dairy cattle of the Czech Republic using individual test-day records. Livestock Research for Rural Development, 21 . Rhone, J. A., Koonawootrittriron, S., Elzo M.A. (2008) Factorsaffecting milk yield, milk fat, bacterial score, and bulk tank somatic cell count of dairy farms in the central region of Thailand. In Tropical animal health and production, 40 (2), 147-153. Saravanan, R., Das, D. N., De, S., Panneerselvam, S. (2015) Effect of season and parity on somatic cell count across zebu and crossbred cattle population. Indian J. Anim. Res., 49, 383-387. DOI: https://dx.doi.org/10.5958/0976-0555.2015.00127.2 SAS User’s Guide 2002-2003. Version 9.3 (TS1M3). SAS Institute. Inc., Carry. NC. USA. Savic, N. R., Mikulec, D. P., Radovanovic, R. S. (2017) Somatic Cell Counts in Bulk Milk and their Importance for Milk Processing. In: IOP Conference Series: Earth and Environmental Science, 85, p012085. Sharif, A., Muhammad, G. (2008) Somatic cell count as an indicator of udder health status under Modern dairy production: a review. Pakistan Vet. J., 28 (4), 194-200. Souza, G. N., Brito, Jose R. F., Brito, Maria A. V. P., Moreira, Elvio C., da Silva, Marcos V. G. B.(2005) Factors affecting somatic cell counts (SCC) in Brazilian dairy cows. In: Animals and environment. Vol.1: Proceedings of the XII-th ISAH Congress on Animal Hygiene, Warsaw, Poland, 4-8 September 2005, BEL Studio sp. zoo., 237-240. Tancin, V., Miklas, S., Macuhova, L. (2018) Possible physiological and environmental factors affecting milk production and udder health of dairy cows: a review. Slovak J. Anim. Sci., 51 (1), 32–40. The Breeding Service of the Slovak Republic. S.E., (B.S. SR, S.E.) (2014) Results of dairy herd milk recording in Slovak Republic at control years 2009 to 2013.

Somatic cell counts in bulk milk and their importance for milk processing

Bulk tank milk somatic cell counts are the indicator of the mammary gland health in the dairy herds and may be regarded as an indirect measure of milk quality. Elevated somatic cell counts are correlated with changes in milk composition The aim of this study was to assess the somatic cell counts that significantly affect the quality of milk and dairy products. We examined the somatic cell counts in bulk tank milk samples from 38 farms during the period of 6 months, from December to the May of the next year. The flow cytometry, Fossomatic was used for determination of somatic cell counts. In the same samples content of total proteins and lactose was determined by Milcoscan. Our results showed that average values for bulk tank milk samples were 273,605/ml from morning milking and 292,895/ml from evening milking. The average values for total proteins content from morning and evening milking are 3,31 and 3,34%, respectively. The average values for lactose content from morning and evening milking are 4,56 and 4,63%, respectively. The highest somatic cell count (516,000/ml) was detected in bulk tank milk sample from evening milk in the Winter and the lowest content of lactose was 4,46%. Our results showed that obtained values for bulk tank milk somatic cell counts did not significantly affected the content of total proteins and lactose.

Artificially extending photoperiod improves milk yield in dairy goats and is most effective in late lactation

Short day length (i.e. winter) is associated with reduced milk yield from dairy animals. Dairy cows and sheep have been successfully housed under lights throughout winter to extend the day length and increase milk yield, very little data exists on the effect of extended day length on the milk yield of dairy goats. The current study was conducted over an eight week period from June to August, 2009. A total of 542 Saanan and Saanan British Alpine cross goats were used, all producing ≥1.5L of milk per day, 253 in early lactation (5–20 days in milk) and 289 in late lactation (190–210 days in milk). Does were randomly allocated to either the control or the long day photoperiod (LDPP) groups, both were housed in open sided sheds with the LDPP group exposed to 16h of light, while the other received a natural lighting regime. Milking was conducted by machine and yield was automatically recorded daily. Doe weights were measured at the beginning of the study and subsequently at four-week intervals. Milk and blood samples were collected from a subset (n=30 and n=18 respectively) of animals in each of the four groups, at day 0 and then every four weeks. Milk was analysed for protein, lactose, bulk milk cell count (SCC), fat and solids-not-fat. Blood plasma was assayed for glucose, non-esterified fatty acids (NEFA) and prolactin. Treatment with LDPP significantly increased (P<0.001) milk yield, with the greatest response occurring in late lactation animals, who were producing 20% more milk than their control counterparts (+0.28kg/d). An increase in milk yield was evident by week 1 in late lactation and week 4 in early lactation. Overall, goats exposed to LDPP showed a decrease in milk fat % (P=0.003), milk protein % (P<0.001), milk solids not fat (P<0.001) and somatic cell count (P=0.012), but a slightly higher milk lactose % (P=0.010), when compared to control animals. LDPP increased milk protein (P=0.010), lactose (P=0.032) and SNF yield (P=0.034) in late lactation animals with the response being greater after 8 weeks than after 4 weeks of treatment. Plasma prolactin (P=0.007) and glucose increased with exposure to LDPP while the same animals showed a decrease in plasma NEFA. Liveweight increased (P<0.001) with LDPP exposure, was greater (P<0.001) in late lactation than in early lactation and increased (P<0.001) with week of treatment. Exposure to LDPP significantly increased milk yield and lactation persistence in Australian dairy goats, most substantially in late lactation.

Somatic Cells Count in Cow’s Bulk Tank Milk

The objective of this study was therefore to present factors affecting somatic cell counts in bovine bulk milk as a result of intramammary infections as well as non-infectious factors. The paper presents also the impact of on-farm management practices on the level of bulk milk somatic cell counts and presents quality indicators in bulk tank milk. At the farm level bulk milk bacterial infection takes place through three main sources: bacterial contamination from the external surface of the udder and teats, from the surface of the milking equipment, and from mastitis microorganisms within the udder. The threshold of 200,000 cells/ml identifies bacteriological negative quarters of the udder. The counts of mammary pathogens in bulk tank milk are relatively low, on average not exceeding 1,000 cfu/ml. Environmental pathogens predominate in bulk tank milk samples with somatic cells count <300 × 10(3) ml.

Fat and protein contents, acidity and somatic cell counts in bulk milk of Holstein cows in the Khorasan Razavi Province, Iran

Relationships between total bulk milk somatic cell score (SCS) and milk fat and protein contents and acidity were investigated in the Khorasan Razavi Province, a region that contributes 6.83% of total milk production in Iran. A total of 1476 samples were analysed. Data were obtained by randomly collecting 123 samples of bulk tank milk from 41 dairy farms during April 2006 to March 2007, every month. Milk was analysed for titratable acidity, protein and fat contents and somatic cell counts (direct microscopic cell count and with Somatos, Russia). Microscopic and Somatos somatic cell counts were comparable. Results showed that the season of raw milk production did not have a significant effect on acidity. Milk fat content increased gradually from spring to winter and there were significant differences (P &lt; 0.05) between spring and other seasons. Higher levels of milk protein fractions were observed during the autumn and winter than in other seasons. The highest total bulk milk somatic cell counts were observed in July. Total bulk milk SCS had significant effects (P &lt; 0.05) on acidity and fat and protein contents. Moreover, the level of acidity and fat in milk decreased with increasing SCS. A significant positive relationship was observed between total bulk milk SCS and the protein content of milk. Elevated SCS were associated with lowered milk quality in Holsteins in the Khorasan Razavi Province.

Auswirkungen einer zweijährigen Bestandesbetreuung von Milchviehbeständen hinsichtlich Eutergesundheit, Antibiotikaeinsatz und Nutzungsdauer

Since 2003, the Research Institute of Organic Agriculture (FiBL) is realizing a herd health management programme ("pro-Q" project) focussing on udder health. The objectives of the project are: (1) to reduce antibiotic mastitis treatments, (2) to optimise udder health and (3) to improve longevity, measured as averaged number of herd lactations. The farms get expert advice in prevention and treatment on herd- and animal-level. After 2 years, treatment recordings of the 65 investigated farms showed that antibiotic mastitis therapies were reduced from 38 to 26 treatments per 100 cows and year (equals a reduction of 32%). Lactation numbers of the herds increased significantly by 0.2 lactations from 3.3 to 3.5 lactations per cow. Udder health remained constant over all farms during 2 years: theoretical bulk milk cell counts averaged constantly at around 180000 cells/ml. Improvement of udder health on farm level was significantly influenced by higher somatic cell count when the project started and enhanced by farmer's motivation and farm-veterinarians' commitment to the project.

Use of the DeLaval cell counter (DCC) on goats' milk

Milk quality is measured by a variety of parameters and one of these is the number of somatic cells in the milk. Within the bovine dairy industry there are maximum acceptable levels on bulk milk cell counts and these are being introduced into caprine dairy production. The reference method for cell counting in goats is the direct microscope (DM) method using pyronin Y-methyl green stain, which stains cell DNA. The use of the DeLaval cell counter (DCC) on goats' milk was compared with this reference method. Samples from 102 udder halves were cell counted using the direct microscope method and the DeLaval cell counter (DCC). Each sample was counted twice by two different observers by the DM method and once using DCC. DCC showed large coefficients of regression (1.03) and correlation (0.95) when compared with the DM cell count (F1,199=1080.0; P<0.001). Goat, udder half and reader type were significant factors.

繋ぎ飼いの酪農家における飼養管理要因のバルク乳体細胞数に与える影響

繋ぎ飼いの酪農家における飼養管理要因のバルク乳体細胞数に与える影響

バルク乳の体細胞数の把握を目的とした補助的評価法の検討

To evaluate useful markers for estimating somatic cell counts (SCC) in bulk milk, electronic conductivity (EC), N-acetyl-β-D-glucosaminidase (NAGase) activity, lactate dehydrogenase (LDH) activity, chemiluminescence (CL) units, adenosine triphosphate (ATP) levels and lactoferrin (Lf) concentrations in milk were measured for comparison with their SCC values. The SCC values correlated significantly (P<0.05, 0.01) with both the CL and LDH values. The measurement of ATP in milk appears to have application in estimating SCC levels in bulk milk.

Milk Quality on Danish Farms with Automatic Milking Systems

The bulk-milk quality of 98 Danish farms with automatic milking systems was analyzed from 1 yr before introduction of automatic milking until 1 yr after. Bulk-milk total bacterial count, spores of anaerobes, somatic cell count (SCC), and freezing point increased when automatic milking was introduced and the frequency of milk-quality failures almost doubled. Milk-quality failures were most frequent in the first 3 mo after the start of automatic milking. The increase in spores of anaerobes indicated that the increase in total bacterial count originated partly from contamination of milk from the teat surface and partly from lack of cleaning of the milking equipment or cooling of the milk. The increase in bulk-milk SCC indicated that milk from clinically infected cows and cows with high cell counts was not diverted to the same degree, milking automatically rather than milking conventionally. A self-monitoring program including survey of the bulk-milk quality was established to help farmers in the transition period going from conventional to automatic milking. The program was introduced on 84 farms. Farms on the self-monitoring program reduced bulk-milk cell count. Application of the program did not reduce the frequency of high total bacterial counts and freezing points of the bulk milk to the level of conventional milking. However, the program reduced the overall frequency of milk-quality failures.

Study on risk factors and their association with subclinical mastitis in lactating dairy cows in Trinidad.

A cross-sectional study was conducted on dairy farms in eight milking centres in Trinidad to determine the prevalence of risk factors for mastitis and to assess their relationship to occurrence of subclinical mastitis. The California mastitis test (CMT) was used to determine the prevalence of subclinical mastitis by estimating the somatic cell counts in bulk and composite milk. Of a total of 177 dairy farms studied, 121 (68.4%), 39 (22.0%) and 17 (9.6%) practised semi-intensive, extensive and intensive management systems, respectively. A total of 129 (72.9%), 37 (20.9%) and 11 (6.2%) farms milked cows in parlours, stanchions and pasture/out-on-field, respectively. Based on sanitary practices, 40 (22.6%), 123 (69.5%), and 14 (7.9%) farms were classified as good, fair, and poor, respectively, while 76 (42.9%) and 60 (33.9%) farms reported to rarely experience and frequently experience water shortages, respectively. Amongst the 177 farms, only seven (4.0%) used machine-milking primarily, 152 (85.9%) screened for mastitis as a routine, 18 (10.2%) teat dipped, and 49 (27.7%) practised dry cow therapy. To detect mastitis, of 152 farms involved, 20 (13.2%) used the strip cup while only two (1.3%) employed the CMT. Pipe-borne water delivered directly from the hose was the only source of water to 91 (51.4%) farms while seven (4.0%) and eight (4.5%) farms used only well and surface water (ponds and rivers), respectively. Based on bulk milk samples, the farm prevalence of subclinical mastitis was 60.5% (107 of 177) with a range from 33.3% (centre 5H) to 100.0% (centre 2B). The difference was statistically significant (P < 0.01; chi 2). However, using composite milk, the farm prevalence of subclinical mastitis was 52.5% (93 of 177) with a range from 21.2% (centre 5H) to 92.9% (centre 2B) and again, the difference in prevalence was statistically significant (P < 0.001; chi 2). Subclinical mastitis was detected in 150 (45.0%) of 333 lactating cows screened and the range of prevalence was from 17.9% (centre 5H) to 56.3% (centre 1C). The difference was statistically significant (P < 0.001; chi 2). Of a total of 14 risk factors for mastitis studied which were related to animal husbandry, personnel, mastitis control and water, only two, the herd size and practice of dry cow therapy were significantly (P < 0.05; chi 2) associated with subclinical mastitis. It was concluded that the high prevalence of subclinical mastitis in Trinidad dairy herds could significantly reduce milk production with associated economic loss. Although a majority of the risk factors studied were not found to be significantly associated with the occurrence of subclinical mastitis possibly due to confounding factors, the need to eliminate or reduce these risk factors cannot be over-emphasized.

Management Practices Associated with Low, Medium, and High Somatic Cell Counts in Bulk Milk

Management practices associated with bulk milk somatic cell counts (SCC) were studied for 201 dairy herds grouped into three categories according to bulk milk SCC. The cumulative production of fat-corrected milk over 305 d of lactation and category for bulk milk SCC were highly correlated; herds within the low category had the highest milk production. Differences in bulk milk SCC among the categories were well explained by the management practices studied. This correlation was not only true for the difference between the high (250,000 to 400,000) and low (≤150,000) categories for bulk milk SCC but also for the difference between the medium (150,000 to 250,000) and low categories and the high and medium categories. Management practices that are known to be important for herds in the high category for bulk milk SCC, such as dry cow treatment, milking technique, postmilking teat disinfection, and antibiotic treatment of clinical mastitis, were also found to be important in the explanation of the difference between herds in the medium and low categories for bulk milk SCC. More attention was paid to hygiene for herds in the low category than for herds in the medium or high category. Supplementation of the diet with minerals occurred more frequently for cows in the low category for bulk milk SCC than for cows in the medium and high categories.

Effect of somatic cell count and stage of lactation on the quality and storage life of ultra high temperature milk.

The effects of bulk milk cell count (BMCC) and stage of lactation on the quality and storage characteristics of UHT milk were investigated. The UHT milk was manufactured in a pilot plant using milk of low BMCC from early and late lactation, and milk of high BMCC from early and late lactation. Upon storage at 20 degrees C, early lactation UHT milk gelled far ahead of late lactation milk. Within each stage of lactation, high BMCC milk tended to gel first. Few differences in the organoleptic properties of the UHT milks were observed. It was apparent that the onset of age gelation may not always be related directly to the level of proteolysis, and that other factors influencing milk composition and the reactions between milk components may play more important roles. At a particular stage of lactation, proteolysis induced by mastitis may hasten the onset of gelation.

Effects of somatic cell count and stage of lactation on raw milk composition and the yield and quality of Cheddar cheese.

The effects of somatic cell count and stage of lactation on the yield and quality of Cheddar cheese were investigated. Cheese was manufactured in a pilot scale factory using milk of low bulk milk cell count (BMCC) from herds in early (LE) and late (LL) lactation, and milk of high BMCC from herds in early (HE) and late (HL) lactation. The deleterious effect of an elevated BMCC on product yield and quality in late lactation was clear. Cheese made from LL milk was significantly superior to that made from HL milk for most yield and quality characteristics measured. Stage of lactation also affected cheese yield and quality, as evidenced by the lower recovery of fat and poorer flavour score for cheese from LL milk compared with that manufactured from LE milk. The observed differences could be explained largely by differences in raw milk composition. We conclude that the effect of stage of lactation was magnified by an elevated BMCC, and that many of the problems encountered when processing late season milk could be overcome by containing mastitis at this time.

Studies on the incidence of clinical mastitis and blood levels of vitamin E and selenium in dairy herds in England

In a trial conducted in the south of England in January to February 1989, blood samples were obtained from nine dairy herds with more than 30 cases of clinical mastitis/100 cows and from nine herds with less than 30 cases/100 cows during the previous 12 months. Whole blood glutathione peroxidase (GSHPx) activity and plasma vitamin E concentration were determined for 12 cows in each herd. The mean (+/-sd) values for the herds with the lower incidence of mastitis were 7.57 +/- 1.86 micrograms/ml plasma vitamin E and 23.8 +/- 22.8 U/ml rbc GSHPx activity, compared with 7.74 +/- 1.69 micrograms/ml plasma vitamin E and 20.61 +/- 8.8 U/ml rbc GSHPx activity for the herds with the higher incidence of the disease. These values indicate that the vitamin E levels were generally adequate but that some animals and herds had low GSHPx activities, suggesting that their diets may have contained inadequate selenium. The activities of GSHPx and the vitamin E levels in plasma were not significantly different in the two groups of herds, and no relationship was found between the two nutrients and the incidence of clinical mastitis. However, there was a significant negative correlation between the activity of GSHPx and the bulk milk cell counts in the herds with a low incidence of mastitis suggesting that there was an association between the incidence of subclinical mastitis or inflammation and the selenium status of these herds.

Intramammary infections and risk factors for clinical mastitis in herds with low somatic cell counts in bulk milk.

Ten herds with low somatic cell counts in bulk milk had an incidence of clinical mastitis of only 2.2 per 100 cows whereas 10 other herds with similarly low cell counts had an incidence of 53.6 per 100 cows. The major pathogens in the herds with a high incidence were Escherichia coli, Streptococcus uberis, Staphylococcus aureus and the coagulase-negative staphylococci. The percentage of uninfected quarters in the herds with a high incidence of clinical mastitis was 21.4 per cent compared with 12.2 per cent in the herds with a low incidence of clinical mastitis. The prevalence of coagulase-negative staphylococci, Corynebacterium bovis and Micrococcus species was higher in the herds with a low incidence of clinical mastitis. There was a significant linear relationship between the percentage of uninfected quarters and the incidence of clinical mastitis in the herds with a high incidence of clinical mastitis. In herds with a low incidence of clinical mastitis significantly less teat disinfection after milking was practised. The results suggest that infections with minor pathogens tend to protect cows against mastitis, and that teat disinfection after milking may increase the percentage of uninfected quarters and lead to an increased risk of clinical mastitis in herds with low somatic cell counts in bulk milk.

Incidence of clinical mastitis on farms with low somatic cell counts in bulk milk.

A total of 1140 clinical cases of mastitis, with at least one inflamed quarter, were reported on 125 farms with somatic cell counts in bulk milk less than 150,000/ml. The average annual incidence was 17.9 cases per 100 cows and ranged from none to 80 cases per 100 cows. The microorganisms most frequently isolated were Escherichia coli (16.2 per cent), coagulase negative staphylococci (13.0 per cent), Staphylococcus aureus (9.6 per cent) and Streptococcus uberis (8.0 per cent). Only two cases of Streptococcus agalactiae were found. As the incidence of clinical mastitis increased, the proportion of S aureus also increased, while the proportions of E coli, S uberis and Streptococcus dysgalactiae remained about the same. Most of the clinical cases of mastitis occurred in early lactation, in November, December and January. However, after correction for the number of calvings per month, the incidence of mastitis was highest in the early summer months.

Mastitis in a large, zero-grazed dairy herd.

A zero-grazed herd of approximately 400 cows had a significant mastitis problem associated with Escherichia coli and Streptococcus uberis during a study over three and a half years. Dry cow therapy and post-milk teat dipping effectively controlled staphylococci and the bulk milk cell count averaged less than 400 X 10(3) cells/ml, but over 1800 clinical cases of mastitis occurred over this period, 32 per cent of which were associated with E coli and 25 per cent with Str uberis. Only 8 per cent of the cases associated with E coli showed obvious systemic disturbance and 75 per cent were cured following penicillin and streptomycin treatment. The incidence was highest during spring and summer when the housed cows were dirtiest. Gross teat-end contamination came mainly from sources other than cubicle bedding, and changing the bedding from sawdust to sand did not alter the incidence of clinical mastitis. It was not possible to maintain adequate cleanliness either inside or outside the parlour, nor maintain a trouble-free milking apparatus. The costs of mastitis in this herd during one year are calculated.

Investigations into falsely elevated somatic cell counts of bulked herd milk.

Bulk milk cell counts obtained by a Coulter Milk Cell Counter were shown to be falsely elevated because of the formation of non-cellular particles (NCP). The NCP, which were detected by the use of a particle size analyser, were removed if the milk samples were heated to 55 degrees C for 15 min before the addition of formalin. A survey of bulk milk supplies in New South Wales showed that NCP occurred in milk from 2% of farms, the counts being falsely elevated by about 200 000 cells/ml. Surveys of milking equipment of farms where the bulk milk had shown this phenomenon demonstrated a relationship between the use of centrifugal milk pumps and the presence of NCP with a much lower prevalence in herds where spit chamber releasers were used. These particles were not air bubbles since air was removed from the milk by heating to 60 degrees C for 15 min, vacuum at 65 mmHg for 15 min or 0.5% v/v octan-2-ol; only the heat treatment removed the NCP.