Pelvic dimensions in phenotypically double-muscled Belgian Blue cows.

Some anatomical characteristics of 507 Belgian Blue (BB) cattle, withers height (WH), heart girth (HG), the distance between the two tubera coxae (TcTc) and the distance between the two tubera ischiadica (TiTi), were compared with the internal pelvic measurements of width, height and area. Mean values were 58.9 ± 6.2 cm for TcTc, 14.6 ± 2.3 cm for TiTi, 15.2 ± 2.1 cm for pelvic width (PW), 18.8 ± 1.9 cm for pelvic height (PH) and 288.5 ± 60.9 cm(2) for pelvic area (PA). Cows that calved per vaginam had larger WH (p < 0.05), TcTc (p < 0.05) and TiTi (p < 0.001) and internal pelvic measurements [PH and PA (p < 0.001)] compared with those whose parturition was managed by caesarean section (CS): Correlations between internal pelvic measurements and TcTc were higher (r = 0.58-0.63) than TiTi (r = 0.22-0.28). Correlations between other external body measures such as HG and WH with the internal pelvic measurements were even higher for HG (r = 0.69-0.74) and for WH (r = 0.67-0.74). HG and WH, together with internal pelvic measures, may be added to estimated breeding values (EBV's) that should assist breeders in selecting cows that can calve per vaginam, thereby reducing the breed's dependence on elective CS for maintaining its unique characteristics.

Analysis of body measurements of newborn purebred Belgian Blue calves.

At calving, purebred animals of the Belgian Blue (BB) breed are compromised by the incompatibility in size and shape of the dam and her calf, resulting in a very high incidence of dystocia problems. To clarify which body parts of the calf are of decisive importance to allow natural delivery and to investigate both the mean value as well as the variation among these body sizes within this breed (variation being an important condition for selection), measurements of nine body parts (body weight at birth (BW), body length (BL), length of the head (LH), shoulder width (SW), hip width (HW), heart girth (HG), withers height (WH) and the circumference of the fetlock of both the front (CFF) and the hind leg (CFH)) were assessed in 147 newborn purebred BB calves on 17 farms. Simple and partial correlations were assessed and we examined whether environmental factors (gender of the calf, parity of the cow, type of calving, season of birth and time of measurement after birth) were significantly associated with these specific calf measurements. The mean BW was 49.2 ± 7.1 kg. The average BL was 56.4 ± 4.5 cm and the mean LH was 24.4 ± 2.3 cm. Measurements obtained for SW and HW were 22.4 ± 2.2 and 22.9 ± 2.1 cm, respectively, whereas the mean WH was 71.1 ± 4.7 cm. Measurements of circumferences revealed a CFF of 17.9 ± 1.1 cm, a CFH of 18.0 ± 1.0 cm and a mean HG of 78.0 ± 5.4 cm. Partial correlations of the BW with eight body measurements were significant (P < 0.01) and ranged between 0.17 and 0.85; 0.42 and 0.88; and 0.24 and 0.88 when corrected for gender, parity and type of calving, respectively. BL (P < 0.01) and the CFF and CFH (P < 0.001) are larger in bull calves than in heifer calves. Calves born through caesarean section had broader SW (P < 0.01) and HW (P < 0.01) when compared with calves born after natural calving (defined as born per vaginam without assistance or with slight traction). Sizes of calves born out of multiparous cows were generally larger than of calves born out of heifers (SW: P < 0.001; HW: P < 0.05). As SW and HW are the broadest points of a BB calf, they are both candidates for being the limiting measures for calving ease, but the difference between HW and SW for the total data set was not different from zero (P > 0.05). In contrast to male calves in which no significant difference (between HW and SW) could be found, female calves show the difference between HW and SW that was significantly different from zero (P < 0.001); thus, in female calves, the HW is the most limiting factor of the calf's body. The significant variation in some body measures between the calves and the strong correlation within these sizes raises the possibility of selection towards smaller calves aiming to limit the dystocia problem in the BB breed. Furthermore, on the basis of our results, we were able to build equations for the farmer to use at the moment of calving containing the LH, the CF and the calf's gender to estimate SW and HW, the limiting body parts of the calf to be born naturally. Together with the knowledge of the pelvic size of the dam, this information gives the obstetrician or the farmer a more accurate prediction of the probability of natural calving at parturition.

Efficacy of metaphylactic florfenicol therapy during natural outbreaks of bovine respiratory disease.

The efficacy of an injectable formulation of florfenicol (300 mg/mL) as metaphylactic control of naturally occurring bovine respiratory disease (BRD) was evaluated in two double-blind randomly controlled field studies on two Dutch veal calf herds (A and B). Cattle aged not older than 3 months and in the direct presence of calves with clinical respiratory disease were randomly allocated to treatment with 40 mg/kg florfenicol subcutaneously (s.c.) a positive control treatment (12.5 mg/kg tilmicosin p.o. twice daily for five consecutive days in herd A, and 12.5 mg/kg doxycycline p.o. twice daily for five consecutive days in herd B), or a negative control (one placebo saline s.c. administration on D0). The predominant respiratory pathogens present in pretreatment respiratory samples from affected animals were Mycoplasma bovis and Pasteurella multocida in outbreaks A and B, respectively. Metaphylactic administration of florfenicol resulted in a statistically significant weight gain, decreased rectal temperature for five consecutive days after treatment and decreased metaphylactic failure percentages compared with both positive and negative control groups. In summary, these studies demonstrated that a single s.c. injection of florfenicol is effective and practical for control of the bacterial component of BRD in veal calves.

Concurrent atypical myopathy and equine dysautonomia in two horses.

This report concerns 2 horses that suffered typical clinical signs of atypical myopathy (AM) and equine grass sickness (EGS) concurrently. Clinical details and pathological lesions of the cases are described. EGS and AM are relatively rare diseases and the concurrency of the diseases in the same animals is therefore considered unlikely to be a coincidence. However, it is not suggested that the evidence shows a common aetiology but rather the existence of common predisposing causes.

Evaluation of the epidemiological importance of classical swine fever infected, E2 sub-unit marker vaccinated animals with RT-nPCR positive blood samples.

It has been demonstrated that pigs that have been double vaccinated with an E2 sub-unit marker vaccine and that are infected with classical swine fever virus (CSFV) through a natural contact infection may react positive in a CSFV detecting RT-nPCR test, whereas no virus could be isolated by using the conventional virus isolation (VI) technique. To evaluate whether these vaccinated and infected pigs may spread the virus, three experiments were set up. In the first, susceptible pigs were inoculated with serum originating from vaccinated RT-nPCR positive pigs. In the second, vaccinated RT-nPCR positive pigs were brought into contact with sentinel animals. In the third, vertical transmission was evaluated in RT-nPCR positive vaccinated pregnant gilts. In the first two experiments, no proof of virus transmission was found, whereas in the third vertical transmission was observed. The conclusion is that in vaccinated pigs that are positive in RT-nPCR but negative in VI, the level of circulating virus is probably not high enough for horizontal transmission, whereas vertical transmission of the virus is possible.

Estimating the probability of freedom of classical swine fever virus of the East-Belgium wild-boar population.

A report of the Scientific Committee on Animal Health and Animal Welfare of the European Commission (CEC, 1999.) includes recommendations for setting up monitoring programmes for classical swine fever (CSF) infection in a wild-boar population, based on the assumption that one would detect at least 5% prevalence in a CSF-infected wild-boar population. This assumption, however, is not science based. We propose an alternative method to provide evidence for a wild-boar population being free of CSF and evaluate the efficiency of a surveillance programme that was implemented in Belgium in 1998. In our study, the probability of freedom of CSF-virus was estimated based on 789 samples; these were collected from wild-boars within the surveillance programme (within the three provinces which include 95% of the Belgian wild-boar population) and examined by three diagnostics methods (antibody detection, virus detection and virus RNA detection). A Bayesian framework was used for the estimation, accounting for the diagnostic test characteristics without the assumption of the presence of a gold standard. The median probability of freedom of CSF-virus was estimated at 0.970, with a 95% credibility interval of 0.149-1.000. Independent on the choice of the prior information, the posterior distributions for the probability of freedom of CSF-virus were always skewed close to the upper boundary of 1. This represents a big gain of knowledge since we did not use any prior information for the probability of freedom of CSF-virus and took the uncertainty about the accuracy of the diagnostic methods into account.

Virulence-associated traits in avian Escherichia coli: comparison between isolates from colibacillosis-affected and clinically healthy layer flocks.

Colibacillosis appears to be of increasing importance in layer flocks. The aim of this study was to determine characteristics of avian pathogenic Escherichia coli associated with the occurrence of colibacillosis outbreaks at flock level. Forty E. coli strains originating from layers from healthy flocks ('control isolates'), consisting of 25 caecal and 15 extra-intestinal isolates, were compared with 40 strains isolated from layers originating from colibacillosis-affected flocks ('outbreak isolates'), consisting of 20 caecal and 20 extra-intestinal isolates. The examined characteristics were adhesins, invasivity in T84 cell culture, serum resistance, iron uptake, colicin production, and toxinogenicity. The following traits were significantly more often detected in the outbreak isolates than in the control isolates: tsh, iss, iucA, iutA, irp2, fyuA, iroC, cvaC, colicin and colicin V production. A comparison of the extra-intestinal outbreak isolates and the caecal control isolates yielded the same results as when the caecal isolates, extra-intestinal isolates and total number of isolates of the outbreak and the control group were compared. When comparing the caecal and extra-intestinal isolates within the control and within the outbreak group, no significant differences were detected. The O78 and O2 groups showed significant differences with other O-types and NT strains for prevalence of most of the same characteristics. The combination of type 1 fimbriae, tsh, serum resistance, iss, traT, iucA, fyuA, iroC and colicin or colicin V production was significantly more often present in extra-intestinal outbreak isolates than in extra-intestinal control isolates. Only the combination of serum resistance, fyuA and colicin production was present in all outbreak isolates, with a significantly lower prevalence in the control isolates. None of the characteristics or combinations examined were exclusive to the outbreak isolates.

An experimental infection (II) to investigate the importance of indirect classical swine fever virus transmission by excretions and secretions of infected weaner pigs.

An experiment was set up to investigate the role of excretions and secretions in the indirect transmission of classical swine fever virus (CSFV). In five small pens, 10 weaner pigs (two pigs per pen) were housed and inoculated with CSFV. Experimental infection was successful in all pigs. The infected pigs were kept in the pens for a period of 15 days after which the pens were depopulated and pigs were killed. At the moment of depopulation, all inoculated pigs were visibly clinically diseased and had high fever. Ten hours later the same pens were repopulated with five pairs of susceptible pigs. From inoculation onwards and especially between depopulation and restocking, the pens were neither cleaned nor disinfected. Four days post-repopulation, three of the susceptible pigs were detected positive on virus isolation. A fourth pig was detected positive 2 days later. Later on, the remaining pigs also became infected, most probably due to contact and between pen infections. It can be concluded that transmission of the virus via excretions and secretions succeeded in four of 10 pigs. This result indicates that transmission of CSFV via excretions and secretions can be of importance in a late, clinical stage of disease.

Efficacy of E2-sub-unit marker and C-strain vaccines in reducing horizontal transmission of classical swine fever virus in weaner pigs.

At present, two types of vaccines against classical swine fever (CSF) virus are commercially available: E2 sub-unit marker vaccines and the conventional attenuated live C-strain vaccines. To evaluate the reduction of the horizontal virus transmission, three comparable experiments were carried out in which groups of weaner pigs (vaccinated with a marker vaccine or a C-strain vaccine) were challenged with CSF virus at 0, 7, and 14 days post-vaccination (dpv). Virus transmission was prevented totally when the challenge occurred at 14 dpv with an E2-marker vaccine (0/12 contact pigs positive in virus isolation (VI); R = 0 (0; 1.5)). At 7 dpv, transmission was reduced slightly (5/12 contact pigs positive in VI; R = 1.0 (0.3; 3.0)), whereas at 0dpv, vaccination had no effect on transmission (10/12 contact pigs positive in VI; R = 2.9 (1.5; 10.8)). In the C-strain-vaccinated pigs, no virus transmission was detected even when the challenge was performed at the same day as the vaccination (0/12 contact pigs positive in VI; R = 0 (0; 1.5)).

Colibacillosis in caged layer hens: characteristics of the disease and the aetiological agent.

In Europe, outbreaks of acute mortality in layer flocks due to colisepticaemia have frequently been observed since the mid-1990s. The aims of this study were to describe the disease, to identify the serotypes of the avian pathogenic Escherichia coli (APEC) present in these outbreaks, and to detect the presence of F11 fimbriae and flagella in the isolates. For this purpose, 20 flocks with APEC-associated increased mortality and 20 control flocks matched for age were examined. Weekly mortality rates in the colibacillosis-affected flocks reached 1.71%, versus 0.30% in the control flocks. The maximum cumulative mortality over an entire colibacillosis outbreak reached 9.19%. The disease was often flock and hen house associated, with recurrent outbreaks within one round and in successive rounds in the same house. Disease was usually acute without clinical symptoms. Peritonitis with yolk material deposited in the peritoneal cavity and polyserositis were the main lesions at necropsy. O78 strains were isolated in 15 of the 20 colibacillosis flocks, and in only one of the control flocks. The majority of strains from the control flocks could not be serotyped by the 28 O-antisera used. In general, F11 fimbriae and flagella were present in the majority of the strains. F11 fimbriae were significantly more often found in O78 isolates than in the other serotypes, and are thus more often present in isolates from colibacillosis flocks. Strains positive for F11, and for F11 and flagella, were more frequently present in heart and liver of the colibacillosis-affected flocks.

Management practices and heifer characteristics associated with early lactation somatic cell count of Belgian dairy heifers.

Associations between somatic cell counts (SCC) from heifers between 5 and 14 d in milk (DIM) and both herd-management practices and heifer characteristics were studied for 1912 heifers in 159 dairy herds in Flanders (Belgium). In higher-producing herds and in herds with an average calving age of heifers > 27 mo, SCC of heifers was lower than in less-producing herds or in herds with an average calving age < or = 27 mo. Heifers raised in herds with a higher bulk-milk somatic cell count had higher SCC. In herds in which heifers calved on slatted floors, heifers had lower SCC compared with herds in which heifers calved on nonslatted floors. A significant difference in SCC was observed between provinces. At the heifer level, SCC decreased with increasing DIM. On average, heifers calving in April to June had higher SCC, compared with those calving in the other months of the year. In the multilevel regression models, nearly all the variations of SCC resided at the heifer level, indicating that preventive measures against udder health problems in freshening dairy heifers should, in the short term, focus more on factors that vary between heifers than on factors that vary between herds. However, for the long term, the need to identify new, and to implement known, herd-level strategies is important.

Significance of interactions between Escherichia coli and respiratory pathogens in layer hen flocks suffering from colibacillosis-associated mortality.

This study aimed to examine the significance of interactions between Escherichia coli and various respiratory pathogens during outbreaks of colibacillosis-associated mortality in layer hen flocks under field conditions. For this purpose, a case-control study involving 20 control flocks with baseline mortality and 20 flocks with increased mortality due to E. coli septicaemia and polyserositis, was conducted. In each colibacillosis flock, blood samples were taken from 20 hens at the onset of clinical disease and three times thereafter at 2-week intervals. Control flocks of comparable ages were sampled in the same way. Pooled sera, taken at the first and last sampling, were examined for antibody titres against infectious bronchitis virus (IBV) and Newcastle disease virus (NDV), and the individual sera from all four samplings were examined for the presence and/or titres of antibodies against avian pneumovirus (APV), Mycoplasma gallisepticum, Mycoplasma synoviae and Ornithobacterium rhinotracheale. Titre increases were seen for IBV D274 (one control flock) and O. rhinotracheale (one control and one colibacillosis flock). An increase in per cent reactors was seen for APV (one control flock), and for M. synoviae (one control and two colibacillosis flocks). The study failed to detect any consistent interactions between E. coli and the aforementioned pathogens. These results indicate that, at least as observed in this study, outbreaks of increased mortality resulting from colibacillosis are not necessarily associated with IBV, NDV, APV, M. gallisepticum, M. synoviae or O. rhinotracheale infections.

Risk factors associated with colibacillosis outbreaks in caged layer flocks.

Colibacillosis appears to be of increasing significance in layer flocks, but there have been no studies of the risk factors associated with outbreaks. This study aimed to investigate the possible associations between risk factors of non-infectious nature and outbreaks of mortality due to colibacillosis in flocks of caged layer hens. Information on management, biosecurity measures and housing conditions was collected in 20 flocks suffering from the disease and in 20 clinically healthy control flocks. The data were processed using multiple logistic regression. The statistical analysis demonstrated that an increase in the distance to the nearest poultry farm by 1 km was associated with a six-fold decreased risk of an outbreak of colibacillosis (odds ratio=0.16). Furthermore, a 1 l increase in cage volume per hen was associated with a 33% decrease in the risk of an outbreak (odds ratio=0.75). It was concluded that the distance between poultry farms and the hen density in the cages are important risk factors for outbreaks of colibacillosis in flocks of layer hens.

Transmission of classical swine fever. A review.

Classical swine fever (CSF) is one of the most important viral pig diseases. Basic measures to control epidemics of CSF comprise eradication of infected herds and preventive emptying of herds at risk. Identification of these herds at risk is based on knowledge of the different transmission routes of the virus. Direct transmission of CSF is undoubtedly the most efficient way of CSF virus transmission. Data on indirect transmission are variable and often equivocal. Various indirect transmission routes like swill feeding, wild boar and artificial insemination are well described, and the importance is beyond discussion. Mechanical transmission via vehicles and persons are categorized as very important based upon epidemiological research, whereas in experiments they can only be reproduced under worst case conditions. The role of arthropods, birds, rodents, and other animals in the spread of CSF virus remains doubtful. Active transmission by these has never been demonstrated and also very sparse indications for mechanical transmission are available. Also the role of airborne transmission remains debated. However epidemiological as well as experimental data indicate that airborne spread over short distances is probable.

Risk analysis of the spread of classical swine fever virus through "neighbourhood infections" for different regions in Belgium.

Risk factors associated with the occurrence of "neighbourhood infections" [Epidemiology of classical swine fever. In: Truszczynski, M. (Ed.), Proceedings of the Workshop on Diagnostic Procedures and Measures to Control Classical Swine Fever in Domestic Pigs and the European Wild Boar. Pulaway, Poland, pp. 119-130] during classical swine fever (CSF) outbreaks were examined based on information collected during a CSF-epidemic, which occurred in the East Flanders Province of Belgium in 1994. The only risk factor that was associated with the occurrence of "neighbourhood infections" was a kernel estimation of the intensity of neighbouring herds (P=0.055) [Interactive spatial data analysis. Pearson Education Limited, Harlow, Essex], i.e. the higher the kernel estimation, the higher the risk for the occurrence of neighbourhood infections. In a second part of the study, the likelihood for the occurrence of neighbourhood infections within an area with a 1 km radius was predicted for every Belgian pig herd, assuming that the herd was infected with CSF-virus. For the prediction of these likelihoods, the model resulting from the risk assessment was used. Finally, the predicted likelihoods were transformed into a raster map after applying a smoothing technique. As a result, different areas in Belgium of higher or lower risk for CSF-virus spread through "neighbourhood infections" could be identified on the map. The areas in Belgium where CSF-outbreaks including "neighbourhood infections" occurred in the past decades were all predicted by the model to be of high risk.

Short-term effect of transition from conventional to automated milking on teat skin and teat end condition.

A higher milking frequency, as a consequence of milking with an automated milking system, incorporates a threat to teat condition. To study the effect of transition from conventional to automated milking on teat skin and teat end condition, 40 lactating Holstein-Friesian cows and heifers from a high yielding dairy herd were randomly allocated to either a conventional or an automated milking system group. In the latter group, automated milking was initiated during the study period, while conventional milking was continued in the control group. Teat skin and teat end condition were evaluated weekly on quarter level for all animals from 5 wk before until 8 wk after transition. A high emollient iodine teat dip was used on all cows during the study period. Teat skin condition of the animals in the automated milking system group was consistent from before and during milking with the automated milking system. Rear teats had a better skin and end condition than front teats. Evolution of teat end condition over time between the automated and conventional milking groups was not statistically different. Heifers, however, seemed to be more sensitive to the change than multiparous cows, as their teat end condition slightly decreased.

Antimicrobial resistance in livestock.

Antimicrobial resistance may become a major problem in veterinary medicine as a consequence of the intensive use and misuse of antimicrobial drugs. Related problems are now arising in human medicine, such as the appearance of multi-resistant food-borne pathogens. Product characteristics, dose, treatment interval and duration of treatment influence the selection pressure for antimicrobial drug resistance. There are theoretical, experimental and clinical indications that the emergence of de novo resistance in a pathogenic population can be prevented by minimizing the time that suboptimal drug levels are present in the infected tissue compartment. Until recently, attention has been focused on target pathogens. However, it should be kept in mind that when antimicrobial drugs are used in an individual, resistance selection mainly affects the normal body flora. In the long term, this is at least equally important as resistance selection in the target pathogens, as the horizontal transfer of resistance genes converts almost all pathogenic bacteria into potential recipients for antimicrobial resistance. Other factors contributing to the epidemiology of antimicrobial resistance are the localization and size of the microbial population, and the age, immunity and contact intensity of the host. In livestock, dynamic herd-related resistance patterns have been observed in different animal species.

Prepartum teat apex colonization with Staphylococcus chromogenes in dairy heifers is associated with low somatic cell count in early lactation.

A high number of dairy heifers freshen with udder health problems. The prevalence of teat apex colonization (TAC) with Staphylococcus chromogenes, one of the most widespread coagulase-negative staphylococci (CNS) in milk samples from freshly calved dairy heifers, was measured cross-sectionally in non-lactating heifers on eight commercial dairy farms in Belgium. The influence of age on this prevalence, and the association between teat apex colonization with S. chromogenes prepartum and quarter milk somatic cell count (SCC) in early lactation were studied. In total, 492 teat apices were sampled from 123 heifers. The age of the heifers varied from 8 to 34 months. Overall, 20% of the heifers had at least one teat apex colonized with S. chromogenes. Of all teats sampled, 10% were colonized with S. chromogenes. The chance of having at least one teat apex colonized with S. chromogenes increased with age of the heifer. The presence of prepartum teat apex colonization with S. chromogenes was not associated with intramammary infection (IMI) early postpartum with the same bacterium. On the contrary, teat apex colonization with S. chromogenes prepartum appeared to protect quarters in the first few days of lactation from having somatic cell count >or=200000cells/ml milk, commonly accepted as the threshold for intramammary infection.

An experimental infection to investigate the indirect transmission of classical swine fever virus by excretions of infected pigs.

In this experiment transmission of classical swine fever (CSF) virus via excretions of infected pigs was investigated under experimental conditions. Five pairs of pigs were experimentally infected with CSF virus. Eight days after experimental infection, when all pigs were viraemic for at least 3 days, the pens were depopulated and 20 h later, restocked with five pairs of susceptible pigs which stayed in these pens for 35 days. During the first 3 weeks of the experiment, the pens were neither cleaned nor disinfected. During the observation period, none of the susceptible pigs became infected. This result indicates that CSF virus spread via excretions is of minor importance in the early stages of infection. For extrapolation of these findings to the field situation and to increase the validity of the conclusions further research is needed to evaluate the effect of factors like virus strain, interval, ..., that may influence the outcome of the experiment.

Seroprevalence of Actinobacillus pleuropneumoniae serovars 2, 3 and 9 in slaughter pigs from Belgian fattening farms.

Fifty randomly selected fattening pig herds were studied to investigate the epidemiological characteristics of infections with Actinobacillus pleuropneumoniae serovars 2, 3 and 9, and to identify risk factors for their within-herd seroprevalences. Information about 13 farm characteristics was obtained by means of a questionnaire and used to assess potential risk factors for the percentage of slaughter pigs with antibodies against each of the three serovars. The presence of antibodies was measured with an indirect ELISA. The median within-herd seroprevalence for serovar 2 was 58 per cent (range 0 to 100 per cent), for serovar 3, 53 per cent (range 10 to 95 per cent), and for serovar 9, 35 per cent (range 5 to 100 per cent). All but one farm tested positive for A pleuropneumoniae serovar 2, and all the farms were positive for A pleuropneumoniae serovars 3 and 9. There was a positive association (P < 0.05) between each pair of serovars. The within-herd seroprevalence of serovar 2 was significantly associated with the density of pig herds in the municipality (odds ratio [OR] = 1.60; P < 0.05) and with the absence of preventive medication at the start of the fattening period (OR = 2.77; P < 0.10). No significant risk factors were found for serovar 3. The percentage of pigs positive for serovar 9 was significantly associated with a slaughter date in June (OR = 2.30; P < 0.10) and with herds in which the finishing houses were not divided into separate compartments (OR = 2.99; P < 0.05).