Flukicides are widely used to treat infestations of liver fluke in dairy cattle. This could result in flukicide residues in milk if animals are improperly treated or if withdrawal periods are not properly observed. The purpose of this review is to summarise the results of studies on depletion of flukicides from milk and the transfer of flukicide residues to dairy products, if present in the milk. As the depletion of flukicide residues from milk of animals treated during lactation was relatively slow, the studies support the view that the dry period (when milk is not being used for human consumption) is the most suitable time for flukicide treatment. Migration of residues to product occurred at different rates, depending on the drug in question. Generally, concentration of flukicides occurred in cheese, butter and skim milk powder. Pasteurisation or heat treatment during spray drying had no impact in reducing residues.

In order to maintain the quality of Irish milk and meet increasingly demanding specifications, it is necessary to focus on chemical residues in milk, in addition to other quality issues. The objective of the work was to assess the current status of chemical contaminant analysis and to identify technological and knowledge needs. This was achieved through a review of literature with respect to chemical contaminants. Quaternary ammonium compounds (QACs) have been identified as an area of concern for the dairy industry because of the recent reports of QAC residues in dairy products internationally. Analytical support to analyse QAC residues in milk and dairy products on an ongoing basis is required. Furthermore, the source of QAC residues along the milk production chain needs to be identified. Similarly, analytical support and research is needed in the area of phthalates, to support the development of intervention strategies to reduce contamination, if present. Cephalosporin antibiotics have been a concern for the dairy industry because of the lack of suitable chemical tests to measure these substances.

The objective of this study was to determine the on-farm management factors that are associated with the Bacillus cereus count in raw bulk tank milk using a cross sectional study design. Bulk tank milk quality was monitored for B. cereus on 63 dairy farms between July and August 2012. Bulk tank milk samples corresponding with processor milk collection dates were taken over a two week period prior to the farm visit and tested for B. cereus. The four most recent samples taken prior to the on-farm visit were averaged and log transformed to give the outcome variable; mean log10 B. cereus cfu/mL. On-farm data collection included recording observations and providing a questionnaire on basic hygiene, management factors and cow hygiene scoring. All independent variables were analysed individually with the outcome variable using simple linear regression and one-way ANOVA; a multivariable regression model was subsequently developed. Only significant variables were retained in the final model (P < 0.05). The geometric mean B. cereus count for all milk samples was 40 cfu/mL. The start temperature of the cleaning solution wash, dry wiping teats prior to unit application, the feeding of silage and reusing the cleaning solution more than once were all unconditionally associated (P < 0.10) with the B. cereus count in bulk tank milk but did not enter the final multivariable model. B. cereus count was four times greater (201 cfu/mL) when cows had been housed compared to when they were on pasture (50 cfu/mL). The allocation of fresh grass every 12 h (62 cfu/mL) resulted in a decrease in B. cereus count (166cfu/mL every 24 h or greater). The testing of water for bacteriology was associated with an increase in B. cereus count. In conclusion, this study highlights specific management factors associated with the B. cereus count in bulk tank milk.

In two experiments, the effect of applying hydrated lime as a cubicle bedding material on the microbial count on teat skin and new intramammary infection were evaluated. In experiment 1, dry dairy cows (n=60) were assigned to one of three cubicle bedding treatments for a 5 week period. The treatments applied were: Hydrated lime (HL), HL (50%) + Ground limestone (50%) (HL/GL) and GL. In experiment 2, two teat disinfectants products chlorhexidine (CH) and iodine (I) were applied to teats at milking in conjunction with two cubicle bedding materials with lactating cows (n=60) for a sixweek period. The treatments applied were: HLCH; HLI; and GLI. The HL treatment had significantly more teats (P<0.001) with no Staphylococcus spp. or Streptococcus spp. bacteria present compared to GL. There were no differences observed between treatments for California Mastitis Test (CMT) score at calving or somatic cell count (SCC) post-calving. In experiment two, the HLI treatment tended (P<0.08) to have lower bulk milk SCC than the GLI. The average bulk milk SCC over the trial period was 68,000, 54,000 and 83,000 cells/mL for HLI, HLCH and GLI, respectively. The incidences of medium-term teat changes were numerically higher with HLI and there were no differences in the mean hyperkeratosis score between treatments. The mean teat hyperkeratosis scores on day 42 were 2.2, 2.1 and 2.1 for HLI, HLCH and GLI, respectively. The HLI treatment had lower levels of Staphylococcal and Streptococcal bacteria on teats compared to GLI (P<0.001). Hydrated lime could be successfully used as cubicle bedding material for dairy cows if used at the recommended rates with either chlorhexidine or iodine based teat disinfectants.

Mastitis was identified as a priority disease within the Irish dairy industry by both dairy farmers and industry animal health experts, which led to the development of the CellCheck programme. In order to support this programme it was necessary to understand the extent to which mastitis affects farm profit, processor returns and ultimately industry profitability. To this end, an analysis of the impact of mastitis on farm, processor and the overall industry profitability was carried out. The impact of mastitis on farm costs, farm receipts and farm profitability is presented across a range of bulk milk somatic cell count (SCC) categories from <100,000 to >400,000 cells/mL. A meta-analysis of the relationship between SCC and raw milk composition, cheese processing characteristics and cheese composition was carried out and utilised to establish the impact of mastitis on processor returns. As SCC increased, the impact of mastitis on the volume of product that could be produced, net processor returns, milk price and the values per kg of fat and protein were calculated. The farm and processor analysis were then combined to estimate the impact of mastitis on the Irish dairy industry returns, accounting for both farm and processor costs. The analysis suggests that as cell count reduced from >400,000 to <100,000 cells/mL, overall returns to the farm should increase by 4.8 c/L, including the farm and processor related effects. Nationally, if the cell count was reduced by 10%, it would be worth €37.6 million for the Irish dairy industry.

The production of high quality milk is a requirement to sustain a profitable dairy industry and somatic cell count (SCC) values are routinely used to identify subclinical mastitis and define quality standards. The objective of this paper is to review the use of SCC as a diagnostic tool for subclinical mastitis in order to improve milk quality on dairy farms. Mastitis is detected based on inflammation subsequent to intramammary infection (IMI) by pathogenic organisms. Individual cow SCC values are used to detect the inflammation that results from IMI and are necessary to define the prevalence and incidence of subclinical IMI. A threshold of <200,000 cells/mL is considered to be of the most practical value used to define a mammary quarter as healthy. The development of IMI is the most significant factor that influences milk SCC and assessment of monthly values to determine newly and chronically increased SCC can be highly diagnostic for resolving problems with increased bulk tank SCC. Methods to reduce the development of new IMI are well known and adoption of best management practices for milking and herd management have consistently been shown to result in reductions in bulk tank SCC. Implementation of mastitis control programmes can be improved by focusing on three practical recommendations: 1) Farmers should work with their advisors to develop an annual udder health plan that includes clear goals for milk quality. 2) The annual udder health plan should emphasise prevention of new IMI. 3) Farmers must identify and manage chronically infected cows. Proactive management of IMI can be extremely effective in helping farmers produce milk that meets industry standards for milk quality.