Frédéric Rollin

Highly effective SNP-based association mapping and management of recessive defects in livestock

The widespread use of elite sires by means of artificial insemination in livestock breeding leads to the frequent emergence of recessive genetic defects, which cause significant economic and animal welfare concerns. Here we show that the availability of genome-wide, high-density SNP panels, combined with the typical structure of livestock populations, markedly accelerates the positional identification of genes and mutations that cause inherited defects. We report the fine-scale mapping of five recessive disorders in cattle and the molecular basis for three of these: congenital muscular dystony (CMD) types 1 and 2 in Belgian Blue cattle and ichthyosis fetalis in Italian Chianina cattle. Identification of these causative mutations has an immediate translation into breeding practice, allowing marker assisted selection against the defects through avoidance of at-risk matings.

Very low surfactant protein C contents in newborn Belgian White and Blue calves with respiratory distress syndrome

We have studied a respiratory distress syndrome (RDS) occurring in newborn calves of the Belgian White and Blue (BWB) breed that represents the large majority of beef cattle in Belgium. Pulmonary surfactant isolated from 14 BWB newborn calves that died from RDS and from 7 healthy controls was analysed for composition and surface activity. An extremely low content or, in some instances, an absence of surfactant protein C (SP-C) was detected in the RDS samples by Western blotting and differential amino acid analysis [0.03+/-0.01% (w/w) relative to total phospholipids, compared with 0.39+/-0.06% for healthy controls (means+/-S.E.M., P < 0.001)]. The contents of surfactant protein B (SP-B) were similar in RDS and control samples. The crude surfactant samples isolated from RDS calves had higher ratios of total protein to total phospholipid, altered phospholipid profiles and lower SP-A contents. Both crude and organic extracts of RDS surfactant samples showed increased dynamic surface tension compared with healthy controls when evaluated with a pulsating-bubble surfactometer. The addition of purified SP-C to organic extracts of RDS surfactant samples lowered surface tension. Strongly decreased levels of mature SP-C associated with fatal RDS and altered surface activity in vitro have, to the best of our knowledge, not been previously reported. The mechanisms underlying RDS and the decrease in SP-C in BWB calves remain to be established.

TECHNICAL AND METHODOLOGICAL REQUIREMENTS FOR RELIABLE HAEMODYNAMIC MEASUREMENTS IN THE UNSEDATED CALF

The purpose of this study was (1) to evaluate the technical and methodological problems associated with invasive haemodynamic measurements in unsedated cattle; (2) to assess the reproducibility of such measurements both within and between days; and (3) to compare the values with those previously reported.Twenty-one healthy calves, aged from 5.5 to 12 months, were studied. The central venous, the right ventricular, the pulmonary arterial, the pulmonary capillary wedge and the systemic arterial pressures were obtained by means of fluid-filled catheters, and the cardiac output was measured by the thermodilution technique. The heart rate, the stroke volume, the pulmonary and systemic vascular resistances and the pulmonary and systemic ventricular workloads were calculated.An adverse reaction, consisting of severe pulmonary hypertension, tachycardia, tachypnoea and transient weakness, occurred in 7 calves during the catheterization procedures. Such a reaction might be due to a local reflex induced by stimulation of mechano-receptors by the catheter tip. It should be avoided by reducing the manipulation of the catheter as much as possible and by inflating the tip of the balloon when moving it forwards. A comparison of the vascular pressures with those previously reported was difficult because of methodological or technical limitations, such as, for instance, a lack of standardization of the baseline. The reproducibility of the haemodynamic measurements obtained was satisfactory, in contrast to previous studies performed in conscious animals. This was attributed to our animals being better trained to the experimental conditions and emphasizes the importance of reducing mental stress in obtaining reliable haemodynamic measurements in unsedated and potentially uncooperative animals.

Comparison of Four Refractometers for the Investigation of the passive transfer in Beef Calves

BACKGROUND Failure of passive transfer (FPT) in beef calves can be detected by refractometry. Nevertheless, different models of refractometers are available, and few studies compare them for the detection of FPT. OBJECTIVES To compare the accuracy of 4 different refractometers for measuring serum total protein concentrations in comparison with results obtained by the biuret method and, based on the serum IgG threshold of 1,600 mg/mL, to determine, for each refractometer, the optimal serum protein concentrations lowest threshold for successful passive transfer. ANIMALS One hundred and eight healthy beef calves, 3-8 days of age. METHODS Observational study. The concentrations of serum total proteins were determined with 4 different models of refractometers and compared with the biuret method by a Bland-Altman statistical method. The optimal serum protein concentrations lowest threshold for successful passive transfer was determined for each refractometer by receiver operating characteristic (ROC) analysis. In addition, the serum immunoglobulin G (IgG) concentration was compared with the serum gamma-glutamyl transferase (γ-GT) activity and with the total immunoglobulin concentration. RESULTS The refractometric measurements were highly correlated with those obtained by the biuret method. Serum total protein concentration threshold values of 56, 58, 54, and 56 g/L were found respectively for the Atago, Atago ATC, Wolf ATC, and digital ATC refractometers. Immunoglobulins were highly correlated with IgG, whereas γ-GT only reflected colostrum uptake by the calf. CONCLUSIONS AND CLINICAL IMPORTANCE All refractometers could be used for the assessment of passive transfer using their individual serum protein concentration threshold.

Cardiovascular response to acute hypoxia in double-muscled calves

Hypoxic-induced pulmonary hypertension is known to be intensive in the bovine species and sometimes leads to pathological cardiac repercussions. On the other hand, doubled-muscled cattle are predisposed to develop hypoxaemia during exercise and with respiratory diseases. Therefore the purpose of this study was to investigate the cardiovascular response to acute hypoxia in double-muscled calves compared with calves of standard conformation. Pulmonary arterial pressure, electrocardiogram and blood temperature were simultaneously recorded, arterial blood was sampled for blood gas analysis and cardiac output was determined in six Friesian calves and six double-muscled calves of the Belgian White and Blue breed(BWB) when breathing air (fractional inspiratory oxygen concentration [FIO2]: 21 per cent) and when breathing a hypoxic gas mixture (FIO2: 10 per cent). All the absolute values of the measured parameters were significantly (P less than or equal to 0.001) different between the two breeds, except heart rate and arterial blood gas values. The pattern of hypoxic-induced decrease in arterial PO2 was similar in the two breeds of calves, suggesting that the pulmonary exchange capacities during hypoxia are no less efficient in double-muscled calves than in calves of standard conformation. Similarly, the percentage of variation of the mean pulmonary arterial pressure from its normoxic to its hypoxic value was the same in the two breeds of calves, suggesting that double-muscled calves are not predisposed to develop a more precocious or more intense pulmonary hypertension for a given level of hypoxaemia. The significantly smaller normoxic and hypoxic cardiac index and stroke index found in BWB compared with Friesian calves was interpreted as a less efficient cardiac function in double-muscled subjects.

Emergence of bovine ehrlichiosis in Belgian cattle herds

Bovine ehrlichiosis is a tick-borne rickettsial disease caused by Anaplasma phagocytophilum. The disease can also be transmitted to humans. Outbreaks in cattle have been described in many European countries. In Belgium, infections caused by A. phagocytophilum have been reported in humans and dogs; however, this paper details the first report of ehrlichiosis in cattle herds in Belgium. The first case described was in a dairy herd located in eastern Belgium. Clinical signs included hyperthermia, polypnea, and swelling of the limbs. The other case was diagnosed in a second, mixed purpose herd in western Belgium. Within the second herd, all of the affected animals came from the same pasture. All animals in that pasture showed recurrent hyperthermia, and some also showed signs of mastitis and late-term abortions. Blood smears and serology revealed the presence of A. phagocytophilum in the majority of animals with pyrexia. Furthermore, the presence of leptospirosis, Neospora caninum, and Q fever antibodies was tested by serological analysis, but all results were negative. Paired serology for Adenovirus, BHV-4, BHV-1, BVD, PI3, and RSV-B did not show any significant seroconversion. Milk samples from cows affected by mastitis revealed minor pathogens. Fecal testing for the presence of Dictyocaulus viviparus in the first herd was negative. Recurrent pyrexia in pastured cattle is a non-specific sign, and can be related to several different pathogens. Bovine ehrlichiosis is transmitted by the tick species Ixodes ricinus which is known to be present throughout Belgium. Belgian practitioners should include ehrlichiosis in their differential diagnosis when confronted with pastured cattle suffering from recurrent pyrexia.

Effect of a combined iodine and selenium supplementation on I and Se status of cows and their calves.

Iodine (I) and selenium (Se) deficiencies are commonly reported in cattle, however, there are also studies regarding a very high iodine supply. The aim of the study was to determine the long-term effect of I and Se supplementation on non-pregnant cows, pregnant cows and their calves. The hypothalamus pituitary axis was investigated (TSH, T4, T3 assays) during a TRH challenge on non-pregnant cows. Twenty-four cows, half of them pregnant, were assigned into 2 diet-groups, one group with a low I (0.45 ppm) and Se (0.15 ppm) diet (LISe), the other with a high I (5.45 ppm) and Se (0.45 ppm) diet (HISe), for a period of 120 days. Nutritional (plasma iodide, urinary I, plasma Se, I content in colostrum and foetal fluids) and functional (thyrotropin, thyroid hormones, glutathione-peroxidase activity in erythrocytes) markers of I and Se status were assayed in dams at regular intervals for 120 days and in their calves at birth. A TRH challenge was performed on 8 non-pregnant cows at day 110 of the trial. At the end of the study, I and Se nutritional markers were higher in dams in the HISe group, compared to the LISe group, except for plasma Se. At birth, I nutritional markers in calves in the HISe group were higher compared to the LISe group. Reactivity of the pituitary-thyroid-axis was not influenced by I and Se supplementation. I and Se supplementation is efficient in improving newborn status.

Clinical differentiation of malignant catarrhal fever, mucosal disease and bluetongue.

THE 2006/07 outbreak of bluetongue virus infection in northern Europe has been characterised by a higher proportion of cattle showing clinical signs (Thiry and others 2006, Guyot and others 2007). This is not often associated with outbreaks of the disease as it is more usual for cattle to be asymptomatic. Adult cattle have mainly been affected, showing ulcerative and necrotic lesions on the muzzle and in the oral cavity, conjunctivitis, lacrimation and periocular dermatitis, photosensitivity-type skin lesions around the midline (later in the course of disease), a drop in milk yield, mild pyrexia and transient loss of body condition, ulcerative and necrotic skin lesions on the udder, teats and vulva, and oedema of the distal limbs (Guyot and others 2007). Bluetongue was first reported in the UK in September 2007, and there is a real threat of the disease affecting more animals in the country, both from infected midges in the UK and those arriving from continental Europe in wind currents (Gloster and others 2007). This, alongside foot-and-mouth disease (FMD), has led to severe economic consequences in terms of both animal movement restrictions and the export market, and animal welfare. Among the differential diagnoses for bluetongue are malignant catarrhal fever (MCF) and mucosal disease, which are endemic to the UK. The clinical differentiation of these three conditions is therefore highly relevant. The aim of this study was to characterise the clinical findings typical of cases of MCF and mucosal disease, and to compare these with clinical findings characteristic of the recent bluetongue outbreak in northern Europe, to assess their value in differentiating these three conditions. Thirty-eight cases of bluetongue were selected from the database of records of the ambulatory clinic of the Faculty of Veterinary Medicine, University of Liège, from August 2006 to February 2007. The criteria for inclusion were a clinical diagnosis of bluetongue and a positive test result either for detection of antibody by a competitive ELISA or detection of viral nucleic acid by real-time reverse transcriptase-PCR, as described by Toussaint and others (2007). Sixty-six cases of mucosal disease and 11 cases of MCF were selected from the database of records of cattle admitted to the University of Glasgow Veterinary School (UGVS) from January 1989 to June 2007. Cases of mucosal disease were included on the basis of typical pathological changes at postmortem examination and on being antigen-positive (HerdChek BVDV Antigen; Idexx) and antibody negative (Svanovir BVDV-Ab; Svanova) for bovine viral diarrhoea virus (BVDV) by ELISA. Cases of MCF were included on the basis of postmortem examination findings and on being positive for antibody to ovine herpesvirus type 2 (OvHV-2) by an immunofluorescent antibody test (Reid 2004) or for OvHV-2 nucleic acid by PCR (Hussy and others 2001). All cases diagnosed as MCF were antigen-negative for BVDV. All the animals had been subjected to a thorough clinical examination according to standard protocols, albeit with slight differences between the two institutions. Cases of bluetongue were examined on-farm in Belgium, whereas cases of MCF and cases of mucosal disease were examined after being referred to the UGVS clinic. Case data were summarised to determine the most common presenting signs for each disease. A Freeman-Halton extension of Fisher’s exact probability test was performed (VassarStats 2007) to test for significant differences in the frequency of clinical signs between the three conditions (Freeman and Halton Veterinary Record (2007) 161, 858-859

Descriptive Study of 32 Cases of Doxycycline-Overdosed Calves

BACKGROUND Reports of doxycycline-induced toxicity are limited despite common use of this antibiotic to treat infectious respiratory disorders in calves. OBJECTIVE To describe previously unreported kidney lesions and diagnostic test results in doxycycline-overdosed calves and to compare these results with other findings reported previously. ANIMALS Thirty-two calves that presented with adverse effects after receiving high doses of doxycycline as a treatment for mild respiratory disorders. METHOD Retrospective review of medical records. RESULTS Clinical examination identified mainly lethargy, dyspnea, cough, tongue paresia or paralysis associated with dysphagia and sialorrhea, tachycardia, tachypnea, and signs of myopathy. Blood analysis indicated increases in creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and sorbitol dehydrogenase activities and increased serum creatinine and urea concentrations. ECG recordings and Doppler echocardiography examination identified ventricular premature beats and a decrease in left ventricular global and systolic function, respectively. Necropsy and histopathology disclosed necrosis of the myocardium, tongue, and some striated muscles, acute renal tubular necrosis, and fatty degeneration or congestion of the liver. CONCLUSIONS Most of these findings corroborate previous observations made in doxycycline-overdosed calves, and further suggest myocardial and striated muscular toxicity as well as renal toxicity in doxycycline-overdosed calves.

Molecular and clinicopathological diagnosis of non-wildebeest associated malignant catarrhal fever in Belgium

MALIGNANT catarrhal fever (MCF) is a pansystemic infectious disease of domestic cattle and wild ruminants (Plowright 1990). There are two forms of the disease: the African form or wildebeest-associated form (WA-MCF); and the non-African form which is suspected to be sheep-associated. The African form is observed in domestic cattle and a number of wild ruminants that come in contact with calving wildebeests (Connochaetes taurinus) that carry the aetiological agent, alcelaphine herpesvirus 1 (AHV-1), a gammaherpesvirus (Barker and others 1993). The non wildebeest-associated form of MCF, or so-called sheep-associated MCF (SA-MCF), is reportedly observed in animals exposed to lambing sheep. The aetiological agent is suspected to be a gammaherpesvirus, ovine herpesvirus 2 (OHV-2) which shares