Jean-Philippe Roy

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.

Risk Factors Associated with Transmission of Mycobacterium avium subsp. paratuberculosis to Calves within Dairy Herd: A Systematic Review

BACKGROUND Paratuberculosis has a worldwide distribution and many countries have implemented control programs to prevent transmission among and within herds. For these programs to be efficient, knowledge of the risk factors involved in transmission is essential. OBJECTIVES Systematically review the scientific literature concerning risk factors associated with Mycobacterium avium subsp. paratuberculosis (MAP) transmission to dairy calves. STUDY DESIGN Systematic review. METHODS An electronic search was done in PubMed and CAB to retrieve references relevant to answer at least 1 of the 5 questions concerning neonatal environment, colostrum, milk, housing of calves, and contact of calves with adult cow feces as risk factors in MAP transmission. A 1st screening was done using titles only, then abstracts, and finally full-length articles were reviewed for relevance. From the articles selected, risk factors and presence of a significant association between these risk factors and MAP transmission were recorded. RESULTS Twenty-three articles from 11 different countries and published in 12 different journals were reviewed. The most common study design was cross-sectional (n = 16). The case definition and diagnostic tests used were very variable among studies, but serum ELISA was used in most studies (n = 14). The study unit was the herd in 18 studies. CONCLUSIONS AND CLINICAL IMPORTANCE The contact of calves with adult cow feces is the most important risk factor in MAP transmission. The 5 categories of risk factors are linked to one another.

Evaluation of selective dry cow treatment following on-farm culture: Risk of postcalving intramammary infection and clinical mastitis in the subsequent lactation

The objective of the study was to evaluate the utility of a Petrifilm-based on-farm culture system when used to make selective antimicrobial treatment decisions on low somatic cell count cows (<200,000 cells/mL) at drying off. A total of 729 cows from 16 commercial dairy herds with a low bulk tank somatic cell count (<250,000 cells/mL) were randomly assigned to receive either blanket dry cow therapy (DCT) or Petrifilm-based selective DCT. Cows belonging to the blanket DCT group were infused with a commercial dry cow antimicrobial product and an internal teat sealant (ITS) at drying off. Using composite milk samples collected on the day before drying off, cows in the selective DCT group were treated at drying off based on the results obtained by the Petrifilm on-farm culture system with DCT + ITS (Petrifilm culture positive), or ITS alone (Petrifilm culture negative). Quarters of all cows were sampled for standard laboratory bacteriology on the day before drying off, at 3 to 4d in milk (DIM), at 5 to 18 DIM, and from the first case of clinical mastitis occurring within 120 DIM. Multilevel logistic regression was used to assess the effect of study group (blanket or selective DCT) and resulting dry cow treatment (DCT + ITS, or ITS alone) on the risk of intramammary infection (IMI) at calving and the risk of a first case of clinical mastitis between calving and 120 DIM. According to univariable analysis, no difference was observed between study groups with respect to quarter-level cure risk and new IMI risk over the dry period. Likewise, the risk of IMI at calving and the risk of clinical mastitis in the first 120 DIM was not different between quarters belonging to cows in the blanket DCT group and quarters belonging to cows in the selective DCT group. The results of this study indicate that selective DCT based on results obtained by the Petrifilm on-farm culture system achieved the same level of success with respect to treatment and prevention of IMI over the dry period as blanket DCT and did not affect the risk of clinical mastitis in the first 120 d of the subsequent lactation.

Comparison of 2-step laparoscopy-guided abomasopexy versus omentopexy via right flank laparotomy for the treatment of dairy cows with left displacement of the abomasum in on-farm settings.

OBJECTIVE To compare characteristics and results of 2-step laparoscopy-guided abomasopexy versus omentopexy via laparotomy in the right paralumbar fossa for the treatment of dairy cows with a left displaced abomasum (LDA). DESIGN Prospective clinical trial. 253 dairy cows with an LDA. PROCEDURES All cows that were treated with omentopexy (n = 101) or 2-step laparoscopy-guided abomasopexy (152) from July 2005 through December 2006 were included. Presurgical, perisurgical, and postsurgical information was recorded by attending veterinarians. Producers were interviewed by telephone 7 and 60 days after surgery regarding the response of cows to surgery. Characteristics of and responses to the 2 surgical techniques were compared. RESULTS At 7 days after surgery, the 2 groups of cows were not significantly different with respect to appetite, comfort, and milk yield; at 60 days after surgery, groups were similar with respect to milk yield, cull rates, and risk of relapse of LDA. Antimicrobial treatment in response to postsurgical pyrexia was necessary in only 20.4% (31/152) of cows that were treated with 2-step laparoscopy-guided abomasopexy. Mean duration (preparation and surgery) of 2-step laparoscopy-guided abomasopexy was significantly less than that of omentopexy (36 vs 74 minutes, respectively). CONCLUSIONS AND CLINICAL RELEVANCE Results of 2-step laparoscopy-guided abomasopexy and omentopexy via laparotomy in the right paralumbar fossa were not significantly different. Compared with omentopexy, laparoscopy-guided abomasopexy was performed more quickly and required postsurgical administration of antimicrobials less frequently. Although these factors may be of economic consequence to veterinarians and producers, other aspects must also be considered when choosing between techniques.

Systematic Review: What is the Best Antibiotic Treatment for Staphylococcus aureus Intramammary Infection of Lactating Cows in North America?

Staphylococcus aureus is the most prevalent pathogen causing intramammary infections (IMI) in dairy cattle worldwide. New treatment regimens have been evaluated to increase cure rates. A systematic review was conducted to answer this question: what is the best antibiotic treatment for S aureus IMI of lactating cows in North America? Direct comparison between studies (n = 6) was difficult since there was no clinical trial comparing all antibiotics and large variations between study protocols and enrolment and outcome definitions were observed. The best therapeutic option currently available in North America is an extended intramammary therapy for 5 to 8 days.

Evaluation of a 3M Petrifilm on-farm culture system for the detection of intramammary infection at the end of lactation.

The purpose of this study was to evaluate a 3M Petrifilm-based on-farm culture system for the detection of intramammary infection (IMI) in low somatic cell count (SCC) cows (<200,000 cells/mL) at drying off. The main objectives were to determine the test characteristics and the predictive values of the Petrifilm on-farm culture system. The ability of dairy producers to correctly classify cows as infected or uninfected based on Petrifilm culture and a set colony count threshold was also assessed. A total of 360 cows originating from 16 low bulk tank SCC (<250,000 cells/mL) dairy herds were enrolled at drying off. Enrolled cows had an expected dry period of 30-90 days, a SCC<200,000 cells/mL on the last 3 tests prior to drying off, no clinical mastitis in the same time period, and no antibiotic treatment in the last 14 days. Quarter milk samples were collected on the day prior to drying off, and a composite milk sample was created by combining 5 mL of milk from each quarter sample. Composite milk samples were cultured on-farm using the Petrifilm culture system, which provided results within 24h. Quarter milk samples were cultured in a reference laboratory, and the results were aggregated to the cow level. On the day of drying off, the Petrifilm was read by the producer and cows were classified as positive if ≥5 colonies (equivalent to 50 colony forming units/mL) were present. When read by the producer, 47.8% of the cows cultured negative on Petrifilm and were infused with only an internal teat sealant at drying off. The test characteristics of the Petrifilm on-farm culture system were calculated by comparing the producer-derived Petrifilm results to those obtained by standard laboratory culture. The sensitivity and specificity of the Petrifilm on-farm culture system were 85.2% (78.5-90.5) and 73.2% (66.4-79.3), respectively. The negative predictive value of the Petrifilm test system was high (86.6%) when estimated using the prevalence of IMI in this data set, and the positive predictive value was moderate (70.9%). An automated 3M Petrifilm reader was used to obtain accurate colony counts. The agreement between Petrifilm results obtained by the producer and those obtained by the automated Petrifilm reader was high, with a kappa value of 0.82 (0.75-0.89).

Minimally Invasive Field Abomasopexy Techniques for Correction and Fixation of Left Displacement of the Abomasum in Dairy Cows

To reduce the potential drawbacks associated with laparotomy techniques for correction and fixation of left displaced abomasums (LDA), minimally invasive techniques have been developed. This chapter reviews the toggle pin suture (TPS) and the laparoscopic abomasopexy procedures used in the field for correction and fixation of the abomasum for correction of left-displacement of the abomasum in dairy cows. The importance of case selection cannot be overestimated. By combining laparoscopy with the principle of the TPS procedure, the lack of visual control associated with the TPS procedure is eliminated, while the advantage of the speed of completion and minimal invasiveness provided by both procedures are maintained. Successful LDA treatment includes not only early detection and treatment of the LDA, but also the prevention of secondary ketosis and aggressive treatment of concurrent disease.

Genetic Structure of Mycobacterium avium subsp. paratuberculosis Population in Cattle Herds in Quebec as Revealed by Using a Combination of Multilocus Genomic Analyses

ABSTRACT Mycobacterium avium subsp. paratuberculosis is the etiological agent of paratuberculosis, a granulomatous enteritis affecting a wide range of domestic and wild ruminants worldwide. A variety of molecular typing tools are used to distinguish M. avium subsp. paratuberculosis strains, contributing to a better understanding of M. avium subsp. paratuberculosis epidemiology. In the present study, PCR-based typing methods, including mycobacterial interspersed repetitive units/variable-number tandem repeats (MIRU-VNTR) and small sequence repeats (SSR) in addition to IS1311 PCR-restriction enzyme analysis (PCR-REA), were used to investigate the genetic heterogeneity of 200 M. avium subsp. paratuberculosis strains from dairy herds located in the province of Quebec, Canada. The majority of strains were of the “cattle type,” or type II, although 3 strains were of the “bison type.” A total of 38 genotypes, including a novel one, were identified using a combination of 17 genetic markers, which generated a Simpsons index of genetic diversity of 0.876. Additional analyses revealed no differences in genetic diversity between environmental and individual strains. Of note, a spatial and spatiotemporal cluster was evidenced regarding the distribution of one of the most common genotypes. The population had an overall homogeneous genetic structure, although a few strains stemmed out of the consensus cluster, including the bison-type strains. The genetic structure of M. avium subsp. paratuberculosis populations within most herds suggested intraherd dissemination and microevolution, although evidence of interherd contamination was also revealed. The level of genetic diversity obtained by combining MIRU-VNTR and SSR markers shows a promising avenue for molecular epidemiology investigations of M. avium subsp. paratuberculosis transmission patterns.

Evaluation of the California Mastitis Test as a precalving treatment selection tool for Holstein heifers

The objective of this study was to evaluate the California Mastitis Test (CMT) and a portable electrical conductivity meter for diagnosing precalving intramammary infection (IMI) in Holstein heifers. A total of 428 dairy heifers from 23 dairy herds were enrolled between 6 and 12 days before the expected calving date from June 2002 to June 2003. Mammary secretions were tested by both diagnostic methods and by bacterial culture for evidence of IMI. California Mastitis Test was considered negative if the score was negative, trace or 1 and was considered positive otherwise. Two cut-off points were evaluated for milk electrical conductivity (>5 and >6.5 mS/cm). From this study, an overall proportion of 69% of heifers had precalving IMI and the overall heifer prevalence of major pathogen IMI was 16.8%. At the quarter level, sensitivity and specificity of CMT (68.9% and 68.4%, respectively) and milk conductivity >5 mS/cm (41.0% and 65.2%, respectively) or >6.5 mS/cm (25.2% and 83.3%, respectively) to identify all IMI were low. However, the heifer level sensitivity and specificity of CMT for major pathogens were 91.0% (81.5-96.6) and 27.5% (22.8-32.6), respectively. Using a cut-off point of 5 mS/cm, the heifer level sensitivity and specificity for major pathogens was 68.7% (56.2-79.4) and 44.1% (38.7-49.6), respectively. A conductivity cut-off value of 6.5 mS/cm decreased the sensitivity and increased the specificity to 53.7% (41.1-66.0) and 59.5% (54.0-64.8), respectively. California Mastitis Test and milk electrical conductivity are not good predictors of major pathogen IMI in heifers during the last 2 weeks before calving. However, the negative predictive values at quarter or heifer level were high and the heifer false negative rate was 6-14% using CMT or conductivity, respectively. Therefore, these measures could be useful for screening out heifers or quarters that are unlikely to have a major pathogen IMI.

Distribution of non-aureus staphylococci species in udder quarters with low and high somatic cell count, and clinical mastitis

The effect of non-aureus staphylococci (NAS) in bovine mammary health is controversial. Overall, NAS intramammary infections (IMI) increase somatic cell count (SCC), with an effect categorized as mild, mostly causing subclinical or mild to moderate clinical mastitis. However, based on recent studies, specific NAS may affect the udder more severely. Some of these apparent discrepancies could be attributed to the large number of species that compose the NAS group. The objectives of this study were to determine (1) the SCC of quarters infected by individual NAS species compared with NAS as a group, culture-negative, and major pathogen-infected quarters; (2) the distribution of NAS species isolated from quarters with low SCC (<200,000 cells/mL) and high SCC (≥200,000 cells/mL), and clinical mastitis; and (3) the prevalence of NAS species across quarters with low and high SCC. A total of 5,507 NAS isolates, 3,561 from low SCC quarters, 1,873 from high SCC quarters, and 73 from clinical mastitis cases, were obtained from the National Cohort of Dairy Farms of the Canadian Bovine Mastitis Research Network. Of quarters with low SCC, high SCC, or clinical mastitis, 7.6, 18.5, and 4.3% were NAS positive, respectively. The effect of NAS IMI on SCC was estimated using mixed-effect linear regression; prevalence of NAS IMI was estimated using Bayesian analyses. Mean SCC of NAS-positive quarters was 70,000 cells/mL, which was higher than culture-negative quarters (32,000 cells/mL) and lower than major pathogen-positive quarters (129,000 to 183,000 cells/mL). Compared with other NAS species, SCC was highest in quarters positive for Staphylococcus capitis, Staphylococcus gallinarum, Staphylococcus hyicus, Staphylococcus agnetis, or Staphylococcus simulans. In NAS-positive quarters, Staphylococcus xylosus (12.6%), Staphylococcus cohnii (3.1%), and Staphylococcus equorum (0.6%) were more frequently isolated from quarters with low SCC than other NAS species, whereas Staphylococcus sciuri (14%) was most frequently isolated from clinical mastitis cases. Finally, in NAS-positive quarters, Staphylococcus chromogenes, S. simulans, Staphylococcus epidermidis, and Staphylococcus haemolyticus were isolated with similar frequency from among low SCC and high SCC quarters and clinical mastitis cases. Staphylococcus chromogenes, S. simulans, S. xylosus, S. haemolyticus, S. epidermidis, S. agnetis, Staphylococcus arlettae, S. capitis, S. gallinarum, S. sciuri, and Staphylococcus warneri were more prevalent in high than in low SCC quarters. Because the NAS are a large, heterogeneous group, considering them as a single group rather than at the species, or even subspecies level, has undoubtedly contributed to apparent discrepancies among studies as to their distribution and importance in IMI and mastitis.