T.J.G.M. Lam

Debunking the myth of the hard-to-reach farmer: Effective communication on udder health

Worldwide, programs to control mastitis are implemented using different strategies to reach farmers. Even though education materials and best practices may be technically optimal, they need to be used to be successful. Thus, effective communication with farmers is essential in order to change their behavior and to improve their farm management. During a Dutch national mastitis control program, a substantial number of farmers seemed to be hard to reach with information on udder health. Consequently, this study was designed to provide insight into the attitude and motivation of such farmers. In the period of October 2007 to July 2008, 24 in-depth, semistructured interviews were conducted with farmers whose veterinarians considered to be difficult to approach with advice on udder health management (8 practices, 3 farmers from each practice). The interviews included questions about the farms and the farmers, their attitude and behavior regarding mastitis, and their information sources and social environment. The results show that so-called hard-to-reach farmers were not always badly informed about udder health and did not always experience problems with mastitis. These ostensibly unreachable farmers were not a homogeneous group, but rather could be divided into 4 categories based on their trust in external information sources regarding mastitis and their orientation toward the outside world: proactivists, do-it-yourselfers, wait-and-see-ers, and reclusive traditionalists. There are ample opportunities to reach hard-to-reach farmers, provided that the communication strategies are tailored to their specific needs. There is especially much to gain in communication with do-it-yourselfers and wait-and-see-ers, but this demands a more proactive role on the part of veterinarians and extension specialists. Different types of farmers need to be approached in different ways and through different channels with information on udder health. Consequently, this study can contribute to the optimization of future programs designed to control and prevent diseases.

QUARTER-MILK SOMATIC CELL COUNT AT CALVING AND AT THE FIRST SIX MILKINGS AFTER CALVING

Thirty cows were studied during the first six milkings after calving. Quarter foremilk samples were collected by the farmers at calving and at six subsequent milkings. Geometric-mean somatic cell count (SCC) decreased from 593,000 at calving to 126,000 cells/ml at the sixth milking after calving. In quarters infected with major pathogenic bacteria, geometric-mean SCC was 3,229,000 cells/ml at calving, and 1,257,000 cells/ml at the sixth milking after calving. In quarters infected with minor pathogenic bacteria, geometric-mean SCC was 1,000,000 cells/ml at calving, and 170,000 cells/ml at the sixth milking after calving. In culture-negative quarters, geometric-mean SCC decreased from 306,000 at calving to 42,000 cells/ml at the sixth milking after calving. Quarter SCC can be used early postpartum to give an indication of intra-mammary infection status.

Production loss due to new subclinical mastitis in Dutch dairy cows estimated with a test-day model

Milk, fat, and protein loss due to a new subclinical mastitis case may be economically important, and the objective of this study was to estimate this loss. The loss was estimated based on test-day (TD) cow records collected over a 1-yr period from 400 randomly selected Dutch dairy herds. After exclusion of records from cows with clinical mastitis, the data set comprised 251,647 TD records from 43,462 lactations of 39,512 cows. The analysis was carried out using a random regression test-day modeling approach that predicts the cow production at each TD based on the actual production at all previous TD. The definition of new subclinical mastitis was based on the literature and assumed a new subclinical case if somatic cell count (SCC) was >100,000 cells/mL after a TD with SCC <50,000 cells/mL. A second data set was created by applying an adjustment to correct low SCC for the dilution effect when determining if the previous test-day SCC was <50,000 cells/ mL. Thereafter, the loss was estimated for records with SCC >100,000 cells/mL. The production (milk, fat, or protein) losses were modeled as the difference between the actual and predicted production (milk, fat, or protein) at the TD of new subclinical mastitis, for 4,382 cow records, and 2,545 cow records after dilution correction. Primiparous cows were predicted to lose 0.31 (0.25-0.37) and 0.28 (0.20-0.35) kg of milk/d at an SCC of 200,000 cells/mL, for unadjusted and adjusted low SCC, respectively. For the same SCC increase, multiparous cows were predicted to lose 0.58 (0.54-0.62) and 0.50 (0.44-0.56) kg of milk/d, respectively. Moreover, it was found that the greater the SCC increase above 100,000 cells/mL, the greater the production losses. The estimated production losses were more precise than previously reported estimates.

Prevalence of Coxiella burnetii infection in Dutch dairy herds based on testing bulk tank milk and individual samples by PCR and ELISA.

A study using an ELISA and a real-time PCR assay based on the detection of the repetitive transposon-like gene of Coxiella burnetii revealed that infection with the bacterium was widespread among Dutch dairy herds, with antibodies detected in bulk tank milk (BTM) from 268 of 341 herds (78.6 per cent) and bacterial DNA detected in 193 of 341 herds (56.6 per cent). The BTM samples were taken in November and December 2007. Serological and molecular studies in young and adult cattle selected from 100 herds showed that antibodies were present in the blood of 470 of 2936 (16.0 per cent) lactating cows but only in 19 of 1831 (1.0 per cent) young animals. Bacterial DNA was detected in the milk of 254 of 2925 (8.7 per cent) lactating cows; bacterial DNA was not detected in any of the faecal samples obtained from youngstock. The blood and milk samples were taken from the cattle in the period January to April 2008.

Prevalence and herd-level risk factors for intramammary infection with coagulase-negative staphylococci in Dutch dairy herds.

In this study, the prevalence of intramammary infection (IMI) with coagulase-negative staphylococci (CNS) in The Netherlands was estimated on 49 randomly selected herds with at least 40 lactating cows. In total, 4220 quarter milk samples were collected. The prevalence of CNS IMI in The Netherlands was estimated at 10.8% at quarter level and 34.4% at cow level, making it the most frequently isolated group of pathogens. Fourteen species of CNS were identified; the most frequently isolated species was Staphylococcus chromogenes (30.3%) followed by Staphylococcus epidermidis (12.9%) and Staphylococcus capitis (11.0%). Prevalence of CNS IMI was higher in heifers compared to older cows. Geometric mean quarter SCC of CNS-positive quarters was 109,000 cells/ml, which was approximately twice as high as culture-negative quarters. Quarters infected with S. chromogenes, S. capitis and Staphylococcus xylosus had a higher SCC (P<0.05) than culture-negative quarters, while quarters that were culture-positive for S. epidermidis and Staphylococcus hyicus tended to have a higher SCC than culture-negative quarters. An increased prevalence of CNS IMI was associated with the herd-level variables source of drinking water not being tap water, housing of dry cows in one group instead of multiple groups, measurement of cow SCC every month, udder health monitoring by the veterinarian, pasturing during outdoor season, percentage of stalls contaminated with milk, and BMSCC>250,000 cells/ml. Although a causal relation between these factors and prevalence of CNS is not proven and for some factors not even likely, knowledge of the associations found may be helpful when approaching CNS problems on dairy farms.

Invited review: Changes in the dairy industry affecting dairy cattle health and welfare

The dairy industry in the developed world has undergone profound changes over recent decades. In this paper, we present an overview of some of the most important recent changes in the dairy industry that affect health and welfare of dairy cows, as well as the science associated with these changes. Additionally, knowledge gaps are identified where research is needed to guide the dairy industry through changes that are occurring now or that we expect will occur in the future. The number of farms has decreased considerably, whereas herd size has increased. As a result, an increasing number of dairy farms depend on hired (nonfamily) labor. Regular professional communication and establishment of farm-specific protocols are essential to minimize human errors and ensure consistency of practices. Average milk production per cow has increased, partly because of improvements in nutrition and management but also because of genetic selection for milk production. Adoption of new technologies (e.g., automated calf feeders, cow activity monitors, and automated milking systems) is accelerating. However, utilization of the data and action lists that these systems generate for health and welfare of livestock is still largely unrealized, and more training of dairy farmers, their employees, and their advisors is necessary. Concurrently, to remain competitive and to preserve their social license to operate, farmers are increasingly required to adopt increased standards for food safety and biosecurity, become less reliant on the use of antimicrobials and hormones, and provide assurances regarding animal welfare. Partly because of increasing herd size but also in response to animal welfare regulations in some countries, the proportion of dairy herds housed in tiestalls has decreased considerably. Although in some countries access to pasture is regulated, in countries that traditionally practiced seasonal grazing, fewer farmers let their dairy cows graze in the summer. The proportion of organic dairy farms has increased globally and, given the pressure to decrease the use of antimicrobials and hormones, conventional farms may be able to learn from well-managed organic farms. The possibilities of using milk for disease diagnostics and monitoring are considerable, and dairy herd improvement associations will continue to expand the number of tests offered to diagnose diseases and pregnancy. Genetic and genomic selection for increased resistance to disease offers substantial potential but requires collection of additional phenotypic data. There is every expectation that changes in the dairy industry will be further accentuated and additional novel technologies and different management practices will be adopted in the future.

Field comparison of real-time polymerase chain reaction and bacterial culture for identification of bovine mastitis bacteria

Fast and reliable identification of the microorganisms causing mastitis is important for management of the disease and for targeting antimicrobial treatment. Methods based on PCR are being used increasingly in mastitis diagnostics. Comprehensive field comparisons of PCR and traditional milk bacteriology have not been available. The results of a PCR kit capable of detecting 11 important etiological agents of mastitis directly from milk in 4h were compared with those of conventional bacterial culture (48h). In total, 1,000 quarter milk samples were taken from cows with clinical or subclinical mastitis, or from clinically healthy quarters with low somatic cell count (SCC). Bacterial culture identified udder pathogens in 600/780 (77%) of the clinical samples, whereas PCR identified bacteria in 691/780 (89%) of the clinical samples. The PCR analysis detected major pathogens in a large number of clinical samples that were negative for the species in culture. These included 53 samples positive for Staphylococcus aureus by PCR, but negative by culture. A total of 137 samples from clinical mastitis, 5 samples from subclinical mastitis, and 1 sample from a healthy quarter were positive for 3 or more bacterial species in PCR, whereas culture identified 3 or more species in 60 samples from clinical mastitis. Culture identified a species not targeted by the PCR test in 44 samples from clinical mastitis and in 9 samples from subclinical mastitis. Low SCC samples provided a small number of positive results both in culture (4/93; 4.3%) and by PCR (7/93; 7.5%). In conclusion, the PCR kit provided several benefits over conventional culture, including speed, automated interpretation of results, and increased sensitivity. This kit holds much promise as a tool to complement traditional methods in identification of pathogens. In conventional mastitis bacteriology, a sample with 3 or more species is considered contaminated, and resampling of the cow is recommended. Further study is required to investigate how high sensitivity of PCR and its quantitative features can be applied to improve separation of relevant udder pathogens from likely contaminants in samples where multiple species are detected. Furthermore, increasing the number of species targeted by the PCR test would be advantageous.

Performance of API Staph ID 32 and Staph-Zym for identification of coagulase-negative staphylococci isolated from bovine milk samples

In this study, the accuracy of two phenotypic tests, API Staph ID 32 and Staph-Zym, was determined for identification of coagulase-negative staphylococci (CNS) from bovine milk samples in comparison with identification based on DNA-sequencing. A total of 172 CNS isolated from bovine milk were classified into 17 species. The most frequently isolated species based on rpoB sequencing were Staphylococcus chromogenes and Staphylococcus epidermidis, followed by Staphylococcus xylosus, Staphylococcus warneri and Staphylococcus equorum (37, 13, 9, 8 and 6% of isolates, respectively). The API Staph ID 32 correctly identified 41% of the CNS isolates. Best agreement with rpoB sequence based species identification was found for S. epidermidis, Staphylococcus hyicus and S. xylosus (100, 89 and 87%, respectively). The positive predictive value was 89, 100 and 52%, respectively. Poor sensitivity was observed for 3 of the 5 most frequently found species, S. chromogenes (37%), Staphylococcus warneri (15%) and S. equorum (0%) albeit with specificity of 100%. The Staph-Zym needed additional tests for 66% of the isolates and identified 31% of the CNS isolates correctly. Good sensitivity was found for S. epidermidis, S. simulans and S. xyloxus (100, 78 and 73%, respectively). The positive predictive value was 89, 78 and 98%, respectively. Poor sensitivity was observed for S. chromogenes, S. warneri and S. equorum (0, 54 and 0%, respectively) but with a specificity of 100, 99 and 100%, respectively. Both phenotypic tests misidentified a large proportion of CNS isolates and were thus unsuitable for identification of CNS species from bovine milk samples.

Prevalence, prediction and risk factors of enteropathogens in normal and non-normal faeces of young Dutch dairy calves.

Abstract Between January and April 2007, 424 calves under 22 days of age from 108 Dutch dairy herds were sampled to estimate the prevalence of non-normal faeces (‘custard-like’—yellowish-coloured with custard consistency or diarrhoea: watery-like faeces) and the shedding of enteropathogens Escherichia coli K99 (E. coli), Coronavirus, Cryptosporidium parvum (C. parvum), Rotavirus and Clostridium perfringens (Cl. perfringens). In addition, information was collected on animal characteristics and herd-management practices. The probability of detecting each one of five enteropathogens given a calf with ‘custard-like’ faeces or diarrhoea was estimated using Bayes’ rule and was based on the predicted probabilities from a multinominal model including each of five enteropathogens as independent variables. In addition, putative risk factors for the presence of each of five enteropathogens were analysed using logistic regression models with random herd effects. Fifty-seven percent of calves had faeces of normal colour (brownish) and consistency (firm), 23.8% (95%CI: 19.8–28.2%) had ‘custard-like’ faeces and 19.1% (95%CI: 15.5–23.2%) had diarrhoea. E. coli was the least detected enteropathogen (2.6% (95%CI: 1.3–4.6%) of calves, 9% (95%CI: 5–16%) of herds) and Cl. perfringens was most detected (54.0% (95%CI: 49.1–58.8%) of calves, 85% (95%CI: 77–91%) of herds). E. coli and Coronavirus were detected incidentally in only one or two calves per herd, whereas C. parvum and Cl. perfringens were frequently detected in up to four calves per herd. For calves with ‘custard-like’ faeces, the probability of detecting Rotavirus from a calf in its first week of age was 0.31 whereas for a calf in its second week, there was a 0.66 probability of detecting C. parvum. The probabilities of detecting E. coli, Rotavirus and C. parvum in calves with diarrhoea in their first week of age were 0.10, 0.20 and 0.43, respectively. In calves with diarrhoea between 1 and 2 weeks of age, the probability of detecting enteropathogens was 0.43 for C. parvum. None of the tested enteropathogens were related to ‘custard-like’ faeces or diarrhoea in the third week of age. Putative risk factors for E. coli, Coronavirus and C. parvum included the presence of peer-calves shedding Coronavirus, C. parvum or Rotavirus, respectively. Additionally, managerial risk factors such as non-optimal hygienic housing (for Coronavirus) and the routine use of antibiotics for diarrhoeic calves (for C. parvum) were found. No animal or managerial factors were associated with shedding of Cl. perfringens.

Identification of Escherichia coli strains from cows with clinical mastitis by serotyping and DNA polymorphism patterns with REP and ERIC primers

A number of Escherichia coli strains was isolated during a study of clinical mastitis on seven farms in the Netherlands. From these E. coli strains, 30 were characterised with regard to their serotype and their DNA polymorphism pattern with REP and ERIC primers. Special attention was given to recurrent E. coli mastitis in cows. The combination of serotype and DNA pattern observed, was used to study the epidemiology of clinical E. coli mastitis. The results demonstrated that the PCR reaction with the ERIC primers can be used for differentiation of E. coli strains. The DNA polymorphism patterns showed that E. coli strains isolated from cases of clinical mastitis have a great variability in genotype. More 3 than one case of clinical mastitis associated with E. coli during the same lactation period occurred infrequently. However when it took place, E. coli strains isolated from the separate episodes of inflammation, were in most instances of the same serotype and had the same DNA amplification pattern.