François Beaudeau

EFFECTS OF DISEASE ON MILK PRODUCTION IN THE DAIRY COW : A REVIEW

Estimates of milk losses consequent to dystocia, stillbirth, milk fever, retained placenta, metritis, cystic ovaries, ketosis, displaced abomasum and locomotor disorders were reviewed. Papers were selected if they provided quantitative estimates of losses based on data collected after 1965, with a sample size resulting in a minimum number of disease cases of 25. Thirty-five papers fulfilled the selection criteria. Milk losses were expressed in kg/day over the period under study to allow comparison of results. Milk fever and cystic ovaries were not associated with yield losses (six studies for each disease). Less than half of the studies found losses associated with dystocia, retained placenta, and metritis, with, respectively, five studies out of 13 (0.3-2.3 kg/day across the lactation), five studies out of 13 (0.8 kg/day across the lactation to 2.5 kg/day across 100 days in milk), and two studies out of 10 (0.4 kg/day across the lactation, and 2.3 kg/day across 119 days in milk). More than half of the studies found losses associated with stillbirth, clinical ketosis, ketosis evidenced by a diagnostic test, and locomotor disorders, with, respectively, three studies out of five (0.7-1.3 kg/day across the lactation), seven studies out of 11 (2.6-5.7 kg/day short-term, and 1.2 kg/day across the lactation), five studies out of seven (1-7 kg/day on the day of diagnosis, and around 1 kg/day across 200 days in milk), and six studies out of 11 (0.3-3.3 kg/day across the lactation). All the five studies, investigating effects of displaced abomasum, found losses (3.5-10.9 kg/day across 80 days in milk, or 0.8-2.5 kg/day across the lactation).

Prevalence of Coxiella burnetii infection in domestic ruminants: A critical review

Reliable detection of Coxiella burnetii is a critical point for the control of the spread of this zoonotic disease (Q fever), ruminants being considered as the main source for human infection as confirmed by the recent human outbreak in the Netherlands since 2007. Considering both public and animal health, providing consolidated prevalence data could be relevant within the decision process of public policy makers or producers organizations. The objective of this study was to conduct a critical review of the literature focused on the prevalence of C. burnetii infection at animal, herd and within-herd levels in cattle, goat and sheep. A qualitative assessment of the 69 selected publications, based on the analysis of the sampling frame and testing procedures, was also performed. While the number of publications increased recently, major methodological issues were still evidenced. These critical issues were related to (i) the absence of description of the sampling strategy and (ii) the lack of sensitivity of the testing procedure. The lack of well designed studies makes not possible to estimate accurately the current prevalence of the infection. Nevertheless, the literature review reported the detection of C. burnetii infection in the all 5 continents with a wide range whatever the species. The apparent prevalence was slightly higher in cattle (20.0% and 37.7% of mean apparent prevalence at animal and herd level respectively) than in small ruminants (around 15.0% and 25% respectively for animal and herd level in sheep and goat). The present conclusions and the current situation support the persistent need of conducting well designed studies, aiming at estimating the true prevalence of C. burnetii infection in the three main domestic ruminant species.

Effects of health disorders on feed intake and milk production in dairy cows

Abstract The purpose of this study was to quantify feed intake decreases and associated milk production losses related to health disorders in dairy cows. Daily individual records of feed intake, milk production and health disorders were available in an experimental farm (107 328 daily records on 1050 lactations from 551 Holstein cows less than 140 DIM). Milk production losses and feed intake decreases were estimated for each health disorder, from 5 days before to a maximum of 140 days after its diagnosis, in comparison to a cow without the disorder, using two separate mixed linear models. On the day of diagnosis, diarrhoea, systemic mastitis, ketosis and milk fever were associated with high reduction in milk production (4.1–25.7 kg) and feed intake (6.7–14.7 kg DM). High cumulated decreases occurred in milk production (109–160 kg) after systemic mastitis, teat injuries and twin calving and in feed intake (46–72 kg DM) after ketosis, systemic mastitis and hock lesions. The average estimated effect of health disorders is a 1.94-kg milk yield loss per kg DM feed intake decrease. This suggests that economical evaluation of health control actions should include associated feed intake decreases.

Risk factors for Salmonella enterica subsp. enterica contamination in French broiler-chicken flocks at the end of the rearing period

Broiler-chicken are often Salmonella carriers. However, these bacteria are responsible for major food-borne human infection, in which poultry-meat products are frequently implicated. In order to prevent Salmonella spread during the slaughtering process, control measures should be implemented at the farm level to reduce the prevalence before slaughtering. The objective of this study was to identify the risk factors for Salmonella contamination in French commercial broiler flocks at the end of the rearing period. A prospective study was carried out in 1996 and 1997 on 86 broiler flocks located in western France. The Salmonella status of the flocks was assessed by means of litter swabs and dust samples analyzed with classical bacteriological methods. Sixty flocks (70%) had at least one contaminated environmental sample and were classified as Salmonella-contaminated flocks. Logistic regression was used to assess association of managerial practices, general hygiene and results of environmental Salmonella recovery, with the odds that the flock itself would be Salmonella-contaminated at the end of the rearing period. Salmonella contamination of the house before placing day-old chicks and the Salmonella contamination of day-old chicks were significantly related to Salmonella contamination of the flock at the end of the rearing period. The risk for Salmonella contamination of the flock was increased when feed trucks parked near the entrance of the change room and when feed meal, instead of small pellets, was provided at the start.

Reduction in milk yield associated with somatic cell counts up to 600 000 cells / ml in French Holstein cows without clinical mastitis

Abstract The reduction in milk yield (kg) on test day associated with individual somatic cell count (SCC) up to 600 000 cells/ml was assessed using monthly cow-records collected for a 1-year period in 105 Holstein herds located in western France. Monthly records with SCC over 600 000 cells/ml, and/or occurring after a clinical case of mastitis were excluded. The resulting dataset comprised 32 148 records from 4968 cows. A mixed autoregressive linear model was used to assess, on test day, the effects on the milk yield (dependent variable) of herd-season (random), SCC (after natural logarithmic transformation), days in milk on which SCC were recorded and an interaction term between SCC and days in milk. Regression coefficients associated with SCC were expressed as a polynomial of days in milk. The reduction in milk yield in kg associated with an increase in SCC was calculated in deviation from a reference SCC value set at 50 000 cells/ml as a function of SCC and days in milk on which SCC were recorded. In primiparous cows, the reduction in milk yield was 0.30 kg for an SCC of 100 000 cells/ml, 0.61 kg for an SCC of 200 000 cells/ml and 1.09 kg for an SCC of 600 000 cells/ml. In multiparous cows, the reduction in milk yield in kg increased with parity and with days in milk. For cows in parity 2 on day 50 pp, the reduction in milk yield was 0.32 kg for an SCC of 100 000 cells/ml, 0.63 kg for an SCC of 200 000 cells/ml and 1.13 kg for an SCC of 600 000 cells/ml. For cows in parity 2 with SCC of 200 000 cells/ml, the reduction in milk yield was 0.63 kg on day 50, 0.92 kg on day 150 and 1.77 kg on day 250 pp. For cows in parity ≥3 on day 50 pp, the reduction in milk yield was 0.30 kg for an SCC of 100 000 cells/ml, 0.60 kg for an SCC of 200 000 cells/ml and 1.07 kg for an SCC of 600 000 cells/ml. For cows in parity ≥3 with SCC of 200 000 cells/ml, the reduction in milk yield was 0.60 kg on day 50, 1.09 kg on day 150 and 1.85 kg on day 250 pp.

Reasons for culling in French Holstein cows

The study describes the profiles of culled cows in order to assess the possible contribution to economic losses due to health disorders. Data regarding dates of birth, final calving and culling, parity at culling, milk yield at the two first test-days of the final lactation and reason(s) for culling were collected in a 5-year survey, carried out from 1989 to 1994 in 84 commercial Holstein farms in western France. Polytomous logistic regression was used to assess the relationship between parity, calving-to-culling interval, milk yield and eight groups of primary culling reasons (i.e. udder disorders; infertility or reproductive disorders; lameness or foot/leg defects; emergency culling reasons; other health disorders; low milk yield; sales for dairy purpose; and other voluntary culling reasons). Out of a total of 5133 culled cows, the proportions of culls, for each of these groups of reasons, were 12.4, 28.4, 2.7, 3.9, 4.6, 16.7, 5.9, and 25.4%, respectively. Cows culled for udder disorders left the herd earlier in lactation and were more frequently at parities 4-6 than cows culled for voluntary reasons. In contrast, cows culled for infertility were younger and culled later within lactation. They were also higher yielding cows than those culled for other reasons. Cows culled for lameness were similar to those of the voluntarily culling group. Cows culled for emergency reasons were more frequently younger cows in early lactation. Cows culled for other health disorders left the herd early in lactation, but at a higher parity than the voluntarily culled cows. These results suggest that most of the culls related to health could be contributing to economic loss. However, special priority should be given to reduce culling for reproductive problems, which is the most costly exit reason.

Incidence of health disorders in dairy farming systems in western France

Abstract Incidence of health disorders was described in 205 dairy farms in Pays de la Loire (France) in 1995/97 and compared between farming systems. Cases recorded by farmers with standard definitions were checked every month during 2 years. Incidences varied widely between herds. Median and mean values were, respectively, in cases per 100 cow-years, 40.2 and 44.1 for clinical mastitis (5.7 and 7.1 systemic mastitis), 7.6 and 10.9 for locomotor disorders, 3.3 and 5.1 for digestive disorders, and, in cases per 100 calvings, 8.1 and 8.8 for retained placenta, 5.2 and 6.6 for dystocia, 4.9 and 5.6 for milk fever, 1.9 and 5.1 for chronic metritis; somatic cell counts exceeded 200 000 cells/ml in 26.6% monthly test-days, d to first artificial insemination (AI) exceeded 90 days postpartum in 25.4% of first AI, and of total AI return rate was 50.4%. In 28% of the herds, health status was characterised by low incidences for all disorders, whereas 10% had high incidences for most disorders, 21% for several peripartum disorders or chronic metritis, 14% for retained placenta and locomotor disorders, 15% for milk fever only and 11% for mastitis only. Incidences varied widely within all farming systems. In each system, every category of herd-health status was present, and more than 20% of the farms had a low-incidence status. Little variation was associated with size of the dairy unit or dairy specialisation of the farm. Non-Holstein herds had less clinical mastitis, better reproductive performance and more dystocia than Holstein herds. Among Holstein systems, clinical mastitis were more frequent in farming systems with highest than with lowest intensification of the dairy production, whereas high somatic cell counts were less frequent. The most intensive group had the highest median incidence for nine out of 14 cow disorders. Variations were higher within than between farming systems.

Rapid identification and quantification of Campylobacter coli and Campylobacter jejuni by real-time PCR in pure cultures and in complex samples

BackgroundCampylobacter spp., especially Campylobacter jejuni (C. jejuni) and Campylobacter coli (C. coli), are recognized as the leading human foodborne pathogens in developed countries. Livestock animals carrying Campylobacter pose an important risk for human contamination. Pigs are known to be frequently colonized with Campylobacter, especially C. coli, and to excrete high numbers of this pathogen in their faeces. Molecular tools, notably real-time PCR, provide an effective, rapid, and sensitive alternative to culture-based methods for the detection of C. coli and C. jejuni in various substrates. In order to serve as a diagnostic tool supporting Campylobacter epidemiology, we developed a quantitative real-time PCR method for species-specific detection and quantification of C. coli and C. jejuni directly in faecal, feed, and environmental samples.ResultsWith a sensitivity of 10 genome copies and a linear range of seven to eight orders of magnitude, the C. coli and C. jejuni real-time PCR assays allowed a precise quantification of purified DNA from C. coli and C. jejuni. The assays were highly specific and showed a 6-log-linear dynamic range of quantification with a quantitative detection limit of approximately 2.5 × 102 CFU/g of faeces, 1.3 × 102 CFU/g of feed, and 1.0 × 103 CFU/m2 for the environmental samples. Compared to the results obtained by culture, both C. coli and C. jejuni real-time PCR assays exhibited a specificity of 96.2% with a kappa of 0.94 and 0.89 respectively. For faecal samples of experimentally infected pigs, the coefficients of correlation between the C. coli or C. jejuni real-time PCR assay and culture enumeration were R2 = 0.90 and R2 = 0.93 respectively.ConclusionThe C. coli and C. jejuni real-time quantitative PCR assays developed in this study provide a method capable of directly detecting and quantifying C. coli and C. jejuni in faeces, feed, and environmental samples. These assays represent a new diagnostic tool for studying the epidemiology of Campylobacter by, for instance, investigating the carriage and excretion of C. coli and C. jejuni by pigs from conventional herds.

Relationship between milk somatic-cell counts in the first lactation and clinical mastitis occurrence in the second lactation of French Holstein cows

The relationship between 10 cell-level descriptors in the first lactation and the risk of clinical mastitis in the second lactation was studied in 10205 Holstein cows from 1254 commercial herds using logistic regression. These 10 cell descriptors were based on the mean cell level over the whole first lactation, on the cell level at the beginning or at the end of the first lactation or on the proportion of cell counts below or above given thresholds. Separate analyses were also performed for subsets of herds defined according to their clinical mastitis incidence risk and their lactation mean somatic-cell count (SCC). Odds of clinical mastitis in second lactation was highest (lowest) for high- (low-) yielding cows. All cell descriptors provided consistent results. Lower (higher) mean cell level, higher (lower) proportion of low SCC values, and lower (higher) proportion of high SCC values in the first lactation were associated with a lower (higher) risk of clinical mastitis in the second lactation. The same trends were observed in all subgroups of herds. Cows with the lowest mean SCC in the first lactation had the lowest risk for clinical mastitis in the second lactation. This suggests that selection for decreased SCC may effectively reduce clinical mastitis incidence and that the breeding goal should favor cows with the lowest observed SCC.

Risk factors for Salmonella persistence after cleansing and disinfection in French broiler-chicken houses.

A prospective survey was carried out in 86 broiler houses in western France to identify risk factors for Salmonella persistence in French broiler houses. The Salmonella status of the house after cleansing and disinfection, was assessed from gauze-swab samples taken from the walls, feeders, ventilation system and bedding (analysed with classical bacteriological methods). Thirty three (38%) houses had at least one contaminated sample and were classified as Salmonella-contaminated houses in the logistic regression. The absence of a terminal disinfection and a disinfection procedure performed by the farm staff rather than a contractor were positively related to the Salmonella contamination of the house after cleansing and disinfection. The risk for Salmonella persistence after decontamination was increased if rodents were observed by the farmer, if a large part of the access area to the house was accessible to trucks, and if a disease leading to a treatment occurred in the previous flock.