Hazard perception of Dutch farmers and veterinarians related to dairy young stock rearing.

A group of 110 dairy farmers and 26 bovine veterinarians participated in a web-based questionnaire using the adaptive conjoint analysis technique to rank their perception regarding several hazards during 6 subsequent periods of the process of dairy young stock rearing. The method applied only involved selected respondents with a high consistency in their answering (correlation >30%). For the ranking, answers were first transformed into a utility score (US) for each hazard. The final ranking for each of the 6 periods was based on the US per hazard separately for farmers and veterinarians. Besides the ranking, the absolute values and the US itself were also compared between farmers and veterinarians to determine any statistically significant differences between the levels of the score despite the ranking. The overall conclusion is that, for almost every designated period, the ranking of the hazards differed between farmers and veterinarians. Only 1 period was observed (period IV, Pregnancy period until 4 weeks before calving) where veterinarians and farmers had the same top 3 ranking of the hazards, namely "Mastitis," "Abortion," and "Poor growth rate of the pregnant heifer." Major differences between farmers and veterinarians were seen during period II (feeding milk until weaning) for the hazard "Diarrhea in older calf," which was considered less important by farmers compared to veterinarians, and period number III (weaning until insemination) for "Over-condition," which, again, was seen as the most important hazard by veterinarians, but only ranked as number 5 by farmers. Besides the ranking, significant differences in absolute US values between veterinarians and farmers were seen in "Infection with Johne's disease" (14.5 vs. 7.8), "Diarrhea in newborn calf" (18.2 vs. 12.2), and "Insufficient feed intake" (16.2 vs. 8.4) in period I (colostrum until transition to milk replacer). Lameness represented the most important significant difference in absolute values in period III (weaning until insemination; 6.3 vs. 14.3), which was again significant in period V (4 wks before calving until calving; 7.4 vs. 12.1). The outcome of this study shows that hazard perception of veterinarians and farmers differs for most rearing periods (in ranking and absolute values). The outcome of this study can be used for 2 purposes: first, to improve communication between farmers and their consulting veterinarian about hazards and hazard perception in young stock rearing; and second, the US scores can be used to select top priority hazards which should at least be integrated into management advisory programs to improve dairy young stock rearing.

Drinking water for dairy cattle: always a benefit or a microbiological risk?

Drinking water can be considered an essential nutrient for dairy cattle. However, because it comes from different sources, its chemical and microbiological quality does not always reach accepted standards. Moreover, water quality is not routinely assessed on dairy farms. The microecology of drinking water sources and distribution systems is rather complex and still not fully understood. Water quality is adversely affected by the formation of biofilms in distribution systems, which form a persistent reservoir for potentially pathogenic bacteria. Saprophytic microorganisms associated with such biofilms interact with organic and inorganic matter in water, with pathogens, and even with each other. In addition, the presence of biofilms in water distribution systems makes cleaning and disinfection difficult and sometimes impossible. This article describes the complex dynamics of microorganisms in water distribution systems. Water quality is diminished primarily as a result of faecal contamination and rarely as a result of putrefaction in water distribution systems. The design of such systems (with/ without anti-backflow valves and pressure) and the materials used (polyethylene enhances biofilm; stainless steel does not) affect the quality of water they provide. The best option is an open, funnel-shaped galvanized drinking trough, possibly with a pressure system, air inlet, and anti-backflow valves. A poor microbiological quality of drinking water may adversely affect feed intake, and herd health and productivity. In turn, public health may be affected because cattle can become a reservoir of microorganisms hazardous to humans, such as some strains of E. coli, Yersinia enterocolitica, and Campylobacter jejuni. A better understanding of the biological processes in water sources and distribution systems and of the viability of microorganisms in these systems may contribute to better advice on herd health and productivity at a farm level. Certain on-farm risk factors for water quality have been identified. A practical approach will facilitate the control and management of these risks, and thereby improve herd health and productivity.

Ranking experts' preferences regarding measures and methods of assessment of welfare in dairy herds using Adaptive Conjoint Analysis.

Welfare in dairy herds can be addressed using different concepts. The difficulty is to extract which measures are the most important to practically address welfare at the herd level and the methods to assess traits considered most important. Therefore, the preferences of 24 acknowledged European welfare experts were ranked regarding 70 measures suitable to assess dairy cattle welfare at herd level using the Adaptive Conjoint Analysis (ACA; Sawtooth Software, Inc., Sequim, WA) technique. The experts were selected on the basis of 3 criteria: at least 5 yr experience in animal welfare research; recent scientific publications in the field of animal welfare; and, at the most, 3 animal species including dairy cattle as their field of expertise. The 70 traits were ranked by using the median ACA questionnaire utility scores and the range between the answers of the 24 experts. A high utility score with a low range between the answers of the experts was considered as suitable to assess welfare at farm level. Measures meeting these criteria were prevalence of lameness cases (107.3±11.7), competition for feed and water (96.4±13.9), and number of freestalls per 10 cows (84.8±13.3). Based on the utility score alone, these former measures were replaced by stereotypic behavior (111.7±17.1), prevalence of lameness cases (107.3±11.7), body condition score (108.0±18.9), and hock lesions (104.7±16.1). Subsequently, to demonstrate that the ACA technique can be used to rank either well-known or inconclusive methods of assessment, the methods for the traits lameness cases and the hygiene of the calving pen were ranked using another 2 ACA questionnaires. The results are based on the opinions of selected, internationally acknowledged dairy cattle welfare experts within the European Union. In the future, other parties like dairy farmers and farmers' organization should be included to achieve consensus about the most suitable traits applicable in practice. The currently investigated traits do not always apply to all dairy husbandry systems across the world, but are based on a system that includes indoor housing during winter. It is concluded that ACA is a useful technique to rank the different scientific opinions of experts regarding suitable traits and methods of assessment of dairy cattle at the herd level.

Capture-recapture analysis of East Coast fever in smallholder dairy herds in the Dar es Salaam region of Tanzania.

The prevalence of and case fatality rate due to East Coast fever (ECF) were estimated in 1402 dairy cattle in 87 small herds in the Dar es Salaam region of Tanzania, from January 2003 to January 2005 using a capture-recapture method. Information on clinical cases and deaths due to ECF were obtained from farm records and from a questionnaire-based cross-sectional survey conducted between July 2003 and March 2005 as part of longitudinal studies of bovine mastitis in these herds. The number of clinical cases identified was 567 (from farm records) and 496 (from the questionnaire), and the number of deaths recorded were 305 (from farm records) and 251 (from the questionnaire). In all, 450 clinical cases and 191 deaths due to ECF were identified from the two sources, giving an observed prevalence of 32% (CI(95%) 30-35%) and observed case fatality rate of 42% (CI(95%) 38-47%). Following application of the capture-recapture method, the estimated number of clinical cases and deaths was 625 (CI(95%) 617-633) and 401 (CI(95%) 384-418), respectively. The respective prevalence and case fatality rates were 45% (CI(95%) 41-48%) and 64% (CI(95%) 60-68%). The estimates obtained using the capture-recapture method are higher than those identified by traditional cross-sectional studies conducted in the same study area, and probably provide a more accurate epidemiological picture of ECF in this region of Tanzania.

Subacute ruminal acidosis in Dutch dairy herds.

The prevalence of subacute ruminal acidosis (SARA) was determined in 197 dairy cows in 18 herds in the Dutch province of Friesland. Samples of rumen fluid were taken by rumenocentesis from between five and 19 animals on each farm and the pH of each sample was determined. The body condition of 139 of the cows was scored approximately three weeks before they calved and three weeks after they calved. The overall prevalence of SARA was 13.8 per cent, and the prevalence on individual farms ranged between 0 per cent (on seven of the farms) and 38 per cent (on one farm). The stage of lactation did not influence the prevalence of SARA but the cows with the condition lost more body condition over the calving period.

Veterinary advice for entrepreneurial Dutch dairy farmers: from curative practice to coach-consultant: what needs to be changed?

Dairy farms are tending to become larger, with a milk quota of more than 8 tons a year, and are managed by entrepreneurial dairy farmers with their own specific characteristics and farming style. Some Dutch veterinary practices appear unable to respond to this different style and often do not serve such farms or lose them as client. Moreover, the veterinary curriculum often focuses on traditional, family-run, smaller dairy operations and not on larger farms, which raises the question whether newly qualified veterinary practitioners are adequately trained to provide these entrepreneurial farmers with the services they require. This article addresses the characteristics of entrepreneurial dairy farmers and those of cattle practitioners, to determine whether cattle practitioners need to acquire other skills to better prepare them for their coaching-consultant tasks on larger dairy farms.

Synthesis of semantic modelling and risk analysis methodology applied to animal welfare.

Decision-making on animal welfare issues requires a synthesis of information. For the assessment of farm animal welfare based on scientific information collected in a database, a methodology called 'semantic modelling' has been developed. To date, however, this methodology has not been generally applied. Recently, a qualitative Risk Assessment approach has been published by the European Food Safety Authority (EFSA) for the first time, concerning the welfare of intensively reared calves. This paper reports on a critical analysis of this Risk Assessment (RA) approach from a semantic-modelling (SM) perspective, emphasizing the importance of several seemingly self-evident principles, including the definition of concepts, application of explicit methodological procedures and specification of how underlying values and scientific information lead to the RA output. In addition, the need to include positive aspects of welfare and overall welfare assessments are emphasized. The analysis shows that the RA approach for animal welfare could benefit from SM methodology to support transparent and science-based decision-making.

Interpretation of California mastitis test scores using Staphylococcus aureus culture results for screening of subclinical mastitis in low yielding smallholder dairy cows in the Dar es Salaam region of Tanzania.

Screening of subclinical mastitis under field conditions is done using the California mastitis test (CMT). CMT score of > or = 1 corresponding to > or = 500,000 somatic cells ml(-1) is commonly used as threshold of subclinical mastitis in temperate countries. However, given the innately high physiological level of somatic cells in low yielding dairy cows, this threshold may not apply to low yielding dairy cows. The current study was undertaken to investigate the clinical utility of CMT for screening of Staphylococcus aureus subclinical mastitis in low yielding smallholder dairy cows in Tanzania. A total of 1151 of quarter-milk samples were CMT tested, of these 914-originated from cows with a lactation period of 14-305 days. All samples were screened for subclinical mastitis by the CMT as well as microbiological culture of single, duplicate (two consecutive) and triplicate (three consecutive) samples as a gold standard. For the duplicate and triplicate quarter-samples, cows were considered positive for S. aureus subclinical mastitis if results of microbiologic culture for S. aureus were positive for two of two, and for at least two of the first three consecutive quarter-milk samples collected from that cow, respectively. Using a CMT score of > or = 1 would classify 78.6% of the 940 quarter-samples as positive. Eighty-two percent of the samples in which S. aureus was isolated had CMT scores > or = 2; this would classify 51.6% of the 940 quarter-samples as positive. For the single sample, this cut-off had sensitivity, specificity and likelihood ratio for S. aureus of 0.87, 0.83 and 4.24, respectively. For the duplicate quarter-milk samples this cut-off had sensitivity, specificity, and likelihood ratio of 0.94, 0.86, and 5.19. While, for the triplicate quarter-milk samples this cut-off had sensitivity, specificity and likelihood ratio of 0.97, 0.92 and 7.47, respectively. Based on these results and practical considerations, it is concluded that CMT score of > or = 2 corresponding to > or = 800,000 somatic cells Ml(-1) is the best cut-off to correctly identify S. aureus intramammary infections in low yielding dairy cows in Tanzania.

Risk factors associated with the incidence rate of clinical mastitis in smallholder dairy cows in the Dar es Salaam region of Tanzania.

Smallholder dairy herds around the Dar es Salaam region of Tanzania supply 86% of raw milk consumed by the city dwellers. Previous studies have indicated that clinical mastitis is an important disease affecting smallholder dairy cows and an 18-month questionnaire-based longitudinal field-study was conducted between July 2003 and March 2005 to elucidate risk factors associated with the incidence. A total of 6057 quarter-level observations from 317 lactating cows on 87 randomly selected smallholder dairy herds were analysed at the quarter and cow level using logistic and Poisson regression models, respectively. At the quarter level, the average incidence rate of clinical mastitis was 38.4 cases per 100 quarter-years at risk whereas at the cow level the incidence rate was 43.3 cases per 100 cow-years at risk. The incidence was significantly (P< or =0.001) associated with cow factors (body condition score, parity, stage of lactation, and udder consistency), housing (floor type) conditions and milking (cow and udder preparation) practices. It was concluded that the extrapolation of the classic ten-point mastitis control plan into smallholder dairy herds should be undertaken cautiously. An integrated approach to dairy extension should focus more on the creation of mastitis awareness among smallholder producers and on the improvement of animal nutrition and reproduction indices-factors that may also have a direct impact on milk yield.

A retrospective study of the aetiology and temporal distribution of bovine clinical mastitis in smallholder dairy herds in the Dar es Salaam region of Tanzania.

A 31-year record-based retrospective study was carried out to determine the aetiology and temporal distribution of bovine clinical mastitis in smallholder dairy herds in the Dar es Salaam region of Tanzania over the period November 1971-December 2002. Laboratory information on 1964 quarter samples from 1365 cows in 281 smallholder dairy herds were retrieved, compiled and studied. Eighty-eight percent of the quarter samples were culture-positive and the predominant mastitis pathogens isolated were Staphylococcus aureus (25.7%), Streptococcus agalactiae (15.4%), Klebsiella pneumoniae (14.3%) and Escherichia coli (14.1%). Other isolates included Pseudomonas aeruginosa (7.5%), Streptococcus dysgalactiae (5.2%) and Streptococcus uberis (4.2%). Contagious mastitis pathogens were isolated from 45.6% of the culture-positive samples, whereas environmental and miscellaneous pathogens were isolated from 48.2% and 5.7%, respectively. Thirty percent of the miscellaneous mastitis pathogens were Candida species. The results demonstrate a steady increase in clinical Candida albicans mastitis. The prevalence of Candida albicans has increased from 1% in 1971 to 17.0% in November 2002. Conversely, despite some fluctuations, the prevalence of Staphylococcus aureus, Streptococcus agalactiae, E. coli and K. pneumoniae remain above 10%. The possible risk factors for these observations are discussed.

Evaluation of the hygienic quality and associated public health hazards of raw milk marketed by smallholder dairy producers in the Dar es Salaam region, Tanzania.

A cross-sectional study was conducted to determine three parameters of the quality of the raw milk marketed by milk selling points (MSPs) in Dar es Salaam region. Total bacterial count (TBC) was used as an indicator of the microbial quality of the milk; antimicrobial residues were determined; and the California mastitis test (CMT) was used to screen for milk somatic cells as an indication of the mastitis level in the cows that provided the milk. Moreover, a water sample at each MSP was taken for bacteriological culturing. Finally, a questionnaire survey was conducted with the milk sellers at the MSPs to identify risk factors for poor milk hygiene. A total of 128 milk samples and corresponding water samples were collected from randomly selected milk selling points in Dar es Salaam region. The mean TBC was (8.2 +/- 1.9) x 10(6) cfu/ml, and major bacterial isolates from the milk samples were Escherichia coli (6.3%), Bacillus cereus (6.3%), Staphylococcus aureus (6.3%) and Streptococcus agalactiae (6.3%), Enterobacter aerogenes (5.6%) and Enterococcus faecalis (4.7%). In most cases, the organisms identified in milk corresponded to those isolated from the corresponding water samples. Of milk samples, 79.0% were positive to the CMT and 7.0% were positive for antimicrobial residues. TBC was normalized by log-transformation, and the possible predictors of TBC were identified by fitting two linear regression models. In a random effect model, water microbial quality, frequency of cleaning the milk containers, frequency of milk supply, milk storage time and the type of containers, and mixing of fresh and previous milk were significantly (p < 0.05) associated with the mean log TBC. In a fixed effect model, in addition to these indicators, water shortage, water source and the refrigerator condition were significantly (p < or = 0.01) associated with log TBC. It was concluded that the milk sold in Dar es Salaam region is of poor quality and is of public health significance.

Veterinary dairy herd health management in Europe: constraints and perspectives.

The nature of veterinary work in dairy health management in Europe has changed over the past years and will change even more dramatically in the near future. The consumers and the media show increasing concern about animal welfare, safety of products of animal origin and traceability of animal products. Farmers in Europe have to produce under strict, often expensive and laborious regulations, while still commercially competing with farmers outside the EU and not subject to the same rules. Veterinarians should adapt their knowledge and skills to the new challenges and developments of the dairy sector. Dairy farmers nowadays ask for support in areas that go beyond clinical activities: environmental protection, welfare, nutrition, grassland management, economics and business management. Bovine practitioners should be able to advise in many different areas and subjects--that is the challenge to our profession. Veterinary education with regards to cattle health management should start with individual animal clinical work, which constitutes the basis of herd health advisory programmes. The bovine practitioner should then look beyond that and regard the herd as the unit. Each diseased cow or group of cows should be detected early enough to avoid financial losses or such losses should be prevented altogether by detecting and managing risk factors contributing to disease occurrence. Herd health and production management programmes represent the first level to optimise dairy farm performance. Expansions to that should further be considered, comprising both animal health and welfare issues, as well as food safety and public health issues. The latter could be addressed by quality risk management programmes following the HACCP-principles. Cattle veterinarians should follow recent developments and invest in new skills and knowledge in order to maintain their usefulness to the modern dairy farmer. Finally we are convinced that the cattle practitioner should evolve into this direction, otherwise the veterinarian as we know him will miss the train in the next years.

The assessment of biomarkers in sentinel cattle for monitoring vanadium exposure.

Various potential biomarkers were sampled for vanadium every 3-4 months from Bos indicus beef cattle farmed extensively immediately adjacent (high exposure (HE) group) and two km away (low exposure (LE) group) from a vanadium processing plant, respectively. Vanadium intake (mg vanadium kg(-1) bwt d(-1)) was modelled using environmental and physiological data as inputs. The vanadium intake ranged from 0.57 to 5.44 mg vanadium kg(-1) bwt d(-1) in the HE group and 0.41 to 2.61 mg vanadium kg(-1) bwt d(-1) in the LE group over a five-year period of monitoring. Samples collected from live sentinel animals over the five-year period included caudal coccygeal vertebrae, tail-switch hair, milk, urine, faeces, rib-bone biopsies and a wide range of blood clinical pathology and haematological parameters. The data was analysed for differences in response between the HE and LE groups. Where differences were found, a linear mixed-effects regression model was fitted to model the relationship between the exposure dose and the response variable. The model included the effects of age, duration of exposure and response, and allowed the prediction of the exposure dose given these inputs. Moreover, forty-two adult cattle were slaughtered over the five years. A wide range of tissue samples, rumen content and whole blood were taken from the cattle at slaughter for vanadium determination. In live animals, a difference in response was found between the HE group and LE group with respect to serum albumin (n = 36), monocyte (n = 36) and thrombocyte (n = 36) counts, and hair (n = 2) and faeces (n = 34) vanadium concentrations. No difference in vanadium concentrations could be shown for urine (n = 36), the traditional occupational health biomarker. Regression models are described for serum albumin, monocyte counts, faeces and hair, which showed the most promise as biomarkers. Average concentrations of vanadium in the tissues of slaughtered cattle ranged from 0.08 to 2.94 mg kg(-1) (wet-weight basis) and rumen content contained 16.67 mg kg(-1). Significant correlations were found between the exposure dose (end-dose) just prior to slaughter and the concentrations of vanadium in the coccygeal vertebrae, liver, diaphragm and rib-bone in descending order of magnitude. Other tissues showed poor correlation to the end-dose. Tissue levels of vanadium in healthy cattle include a much wider range than is currently reflected in the literature. The best tissue from slaughter animals for assessing chronic vanadium exposure is probably the liver.

The public health implications of farming cattle in areas with high background concentrations of vanadium.

Forty-two adult Brahman-cross cattle farmed extensively in two groups, immediately adjacent to and 2 km from a vanadium processing plant respectively, were slaughtered over a 5 year period at a nearby abattoir. Cattle were being exposed to vanadium at close to no-adverse-effect levels. The dose of vanadium that cattle were taking in prior to slaughter was calculated for each animal from environmental and physiological data using a stochastic risk assessment model. The median exposure doses in the month prior to slaughter ranged from 0.55 to 2.73 mg vanadium/kg body weight/day. A range of tissues was taken from the cattle at slaughter for vanadium determination and tissue levels of vanadium in muscle, liver and kidney are reported. The concentrations of vanadium in the milk of cattle from the same farm sampled over 5 years are also reported. Concentrations were further modelled using a lognormal distribution function to look at possible extreme values that are likely to occur. The concentrations of vanadium in commonly consumed tissues ranged from <0.05 to 11.51 mg/kg (wet-mass basis). The median concentration of vanadium in milk was 0.23 mg vanadium/kg. People drinking milk were at highest risk. The potential oral daily intake of vanadium for people consuming these foodstuffs was modelled using a stochastic model. The model predicted that there is less than a 5% chance that the potential daily intake of vanadium from milk will be >0.44 microg/kg/day for adults. Based on this upper limit it was concluded from current knowledge of toxicity in humans that the tissue and milk residues from cattle should pose no health risk to the consumer.

Assessing the repeatability and reproducibility of the Leg Score: a Dutch Claw Health Scoring System for dairy cattle.

The optimal moment for trimming the claws of all dairy cows in a herd was investigated by assessing the external rotation of the hind claws of individual cows relative to the spinal column. This leg score consisted of three independent descriptors: 1 (good/normal), 2 (moderately deviant), and 3 (severely deviant). This study assessed the repeatability and the reproducibility of the leg score system, and the consistency of the advice given subsequently about trimming of the hind claws of all cows in the herd. Repeatability was assessed for 52 cows that were scored twice on the same day by 11 observers; the kappa value ranged from 0.17 to 0.66 (mean: 0.36). The probability of the same result for both assessments ranged from 0.49 to 0.80 (mean: 0.61). Claw trimming was advised if at least 20% of the cows had a leg score of 3. On the basis of the scores, 3 observers consistently advised trimming of the hind claws of all the cows in the herd, and 6 observers consistently advised against the need for trimming in the short term; 2 observers had an inconsistent advice. The reproducibility of the scoring system was assessed in two dairy herds (62 and 50 cows). Eight observers evaluated the leg score of the cows of both herds on the same day. The mean kappa value of the leg score for all pairs of different observers (A-B, A-C etcetera) was 0.24 [-0.08-0.49]. In conclusion, the leg score is not a reliable method for determining the optimal moment for claw trimming in dairy cattle. The reasons for the inconsistent observations require further investigation.

Influence of negative energy balance on the reproductive performance after treatment of cystic ovarian disease with gonadotrophin-releasing hormone in dairy cows.

The aim of this study was to investigate whether a significant relation exists between the presence of a negative energy balance (NEB) in cows early in lactation and the reproductive performance after treatment with gonadotrophin-releasing hormone of cows with clinical cystic ovarian disease. Reproductive performance after treatment was assessed from the interval between treatment and first insemination (ITFI) and the interval between treatment and conception (ITC). Based on the outcome of the daily change of milk fat yield (Deltafatg) between the first and second milk recordings post-partum, cows were considered to have passed the NEB nadir (positive Deltafatg) or not (negative Deltafatg). Lactations (n = 430) were divided into four groups according to the interval between calving and first milk recording (ICMR): (i) 0-9 days; (ii) 10-19 days; (iii) 20-29 days; (iv) 30-49 days. The relation between a NEB-proxy parameter (Deltafatg) and reproductive performance was determined. A significant interaction existed for groups 1 and 3 (ICMR on 0-9 and 20-29 days post-partum respectively) with an increased and a decreased probability of being inseminated the first day after treatment (ITFI) respectively. However, no significant interaction was found between Deltafatg and the groups with regard to ITC.

The Hazard Analysis Critical Control Point's (HACCP) concept as applied to some chemical, physical and microbiological contaminants of milk on dairy farms. A prototype.

Quality management on dairy farms becomes more and more important regarding the different areas of animal health, animal welfare and food safety. Monitoring animals, farm conditions and farm records can be extended with risk identification and risk management. The hazard analysis critical control point's system is useful as an on farm strategy to control the product as well as the production process on the areas of animal health, animal welfare and food safety. This article deals in detail with the question how to develop a qualitative method where risk can be defined as an interaction between probability and impact. Two parts of the production process (milk harvest and treatment of cows) where used as an example how to apply the hazard analysis critical control point's system on chemical, physical and microbiological contaminants of milk. Not just only by summarizing the different critical checkpoints for each area but also by giving them a precise judgement of probability and impact.

Mycobacterium avium ssp. paratuberculosis recombinant heat shock protein 70 interaction with different bovine antigen-presenting cells.

Abstract Heat shock proteins (Hsp) can deliver antigen into the major histocompatibility complex class I presentation pathway of antigen-presenting cells (APC), a process called cross priming, thus stimulating antigen-specific CD8+ T-cell reactions. Hsp were shown to elicit proinflammatory responses in APC. Both processes require interaction of Hsp with APC via specific receptors. This study describes the interaction of recombinant Hsp70 (rHsp70) of Mycobacterium avium subspecies paratuberculosis with bovine peripheral blood mononuclear cells that was restricted to CD14+ cells. Characterized monocyte-derived macrophages, monocyte-derived dendritic cells (DC) and BoMac, an immortalized bovine macrophage cell line, were used to investigate the interaction of rHsp70 with different bovine APC. Saturation of immature DC with high concentrations of rHsp70 is demonstrated, and it was found that interaction of rHsp70 with DC was related to the maturation stage of the DC. Involvement of CD91 as a cellular receptor for rHsp70 was demonstrated; however, competition studies with immature DC demonstrated that other receptors exist on bovine APC. These data suggest that rHsp70-based vaccines may be useful for the successful immunization of cattle.

Effects of polyunsaturated fatty acids on the proliferation of mitogen stimulated bovine peripheral blood mononuclear cells.

The present study aimed at analysis of the effects of polyunsaturated fatty acid (PUFA), linoleic acid (LA, C18:2n - 6) and linolenic acid (LNA, C18:3n - 3) on bovine peripheral blood mononuclear cells (PBMC) in vitro. Both mitogen (ConA)-induced proliferative lymphocyte responsiveness during 4 days of culture and eicosanoid (prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4))) production during 36 h were determined in relation to the absence or presence of various concentrations of LA and LNA (0, 1, 5, 25, 125 and 250 microM). Mitogen-driven proliferative responses of lymphocytes tended to be uninfluenced in the presence of lower concentrations of LA, whereas significant inhibition was observed at the higher concentrations of LA (125 and 250 microM). However, increasing amounts of LNA did not affect the proliferation. ConA stimulation induced a clear PGE(2) response, which significantly decreased in the presence of 250 microM of LA. In addition, increasing amounts of LNA, but not LA, led to a significant decrease in LTB(4) levels. However, The production of LTB(4) did not alter due to mitogenic stimulation. In conclusion, the present study shows that bovine mononuclear cells may functionally be influenced by the presence of PUFA in their environment. Further studies need to be conducted to clarify in vivo consequences of these findings in a situation of PUFA enriched rations in ruminants.

Associations between energy metabolism, LH pulsatility and first ovulation in early lactating cows.

This study was designed to elucidate associations between energy metabolism and LH pulsatility characteristics in early lactation, and days to first ovulation, in order to explain the relationship between energy balance and fertility observed in epidemiological studies. To this end, 10 multiparous HF cows were monitored during lactation, after the application of two different feeding strategies during the dry period. Days to first ovulation was assessed using blood progesterone measurements and LH pulsatility was measured in 8-h windows in the third week postpartum. The association between depth of negative energy balance and days to ovulation was confirmed. However, this study does not support the idea that LH pulsatility characteristics in early lactation are predictive for the interval between parturition and first ovulation.