Cow's health and farmer's attitude towards the culling decision in dairy herds

The study described in this thesis focusses on the health related culling decision in dairy cows, with special attention to the role of farmer's attitude in this process. This thesis is composed of four parts. In the first part, the associations between diseases and culling in dairy cows were reviewed and discussed from the literature. In the second part, the impact of disease on longevity was assessed in terms of risk of culling and in terms of reduced length of productive life. The third part focussed on methodological issues, and proposed a method accounting for within-cow-dependency of lactations to assess diseases as risk factors for culling. The differences between farmers in their culling decision process were specifically studied in the fourth part through the assessment of the associations between farmers' culling decisions and management styles. Applications of the present study and perspectives in the field of herd health management were discussed

Effect of antimicrobial use on the resistance of Escherichia coli in faecal flora of pigs

The antimicrobial use in veterinary medicine is of concern because of possible transmisston of resistant bacteria to humans. However the relation between use and occurrence of resistance is poorly documented in the field. Sixteen farrow-to-fimsh herds were selected and classified on the frequency of antimicrobial administrations (low (LU), medium (MU) and high (HU) users). lndtcative Eschenchia coli strains were tsolated from faeces of sows (5 per herd) and young pigs (3 per sow) at several ttmes during animals\u27 hfe and tested for reststance to amoxicillin, gentamicin, trimethoprim-sulfamids and tetracyclin. The percentages of resistant strams were compared between herd groups

Risk factors for the introduction and within-herd transmission of Mycobacterium avium subspecies paratuberculosis (MAP) infection on 59 Irish dairy herds

Since 1994, Irish cattle have been exposed to greater risks of acquiring Mycobacterium avium subspecies paratuberculosis (MAP) infection as a consequence of the importation of over 70,000 animals from continental Europe. In recent years, there has been an increase in the number of reported clinical cases of paratuberculosis in Ireland. This study examines the prevalence of factors that promote the introduction and within-herd transmission of Mycobacterium avium subspecies paratuberculosis (MAP) on selected Irish dairy farms in the Cork region, and the association between these factors and the results of MAP screening tests on milk sock filter residue (MFR). A total of 59 dairy farms, selected using non-random methods but apparently free of endemic paratuberculosis, were enrolled into the study. A questionnaire was used to collect data about risk factors for MAP introduction and transmission. The MFR was assessed on six occasions over 24 months for the presence of MAP, using culture and immunomagnetic separation prior to polymerase chain reaction (IMS-PCR). Furthermore, blood samples from all entire male and female animals over one year of age in 20 herds were tested by ELISA. Eighteen (31%) farms had operated as closed herds since 1994, 28 (47%) had purchased from multiple sources and 14 (24%) had either direct or indirect (progeny) contact with imported animals. Milk and colostrum were mixed on 51% of farms, while 88% of farms fed pooled milk. Thirty (51%) herds tested negative to MFR culture and IMS-PCR, 12 (20%) were MFR culture positive, 26 (44%) were IMS-PCR positive and seven (12%) were both culture and IMS-PCR positive. The probability of a positive MFR culture was significantly associated with reduced attendance at calving, and with increased use of individual calf pens and increased (but not significantly) if mulitiple suckling was practised. There was poor agreement between MFR culture and MFR IMS-PCR results, but moderate agreement between MFR culture and ELISA test results. This study highlights a lack of awareness among Irish dairy farmers about the effect of inadequate biosecurity on MAP introduction. Furthermore, within-herd transmission will be facilitated by traditional calf rearing and waste management practices. The findings of viable MAP in the presence of known transmission factors in non-clinically affected herds could be a prelude to long-term problems for the Irish cattle and agri-business generally

Detecção molecular e análise filogenética de vírus respiratório sincicial bovino (BRSV) em swabs e tecido pulmonar de bovinos adultos

O vírus respiratório sincicial bovino (BRSV) é um dos agentes etiológicos de pneumonias em bovinos jovens. Poucos estudos foram realizados visando à detecção do agente em amostras coletadas de animais adultos, e em especial de bovinos assintomáticos. No entanto, presume-se que as infecções ocorridas nestes grupos possam ocorrer em sua maioria de forma assintomática e este seria um mecanismo importante para manutenção do BRSV nos rebanhos. No presente estudo, o objetivo foi realizar uma análise da prevalência de infecções assintomáticas pelo BRSV em pulmões (n=68) e swabs nasais (209) coletados de bovinos adultos coletadas em frigoríficos da região Sul e Sudeste respectivamente, no sentido de detectar por intermédio de reação da polimerase em cadeia qual a taxa de animais infectados em populações de animais adultos onde não ocorram sinais clínicos da infecção. As amostras positivas à RT-PCR (6) foram posteriormente submetidas ao corte com enzimas de restrição (REA) e sequenciamento para caracterização genética do gene F (2 das amostras). Todas as amostras se enquadram no subgrupo B de BRSV, o grupo circulante no Brasil conforme estudos anteriores. Os resultados obtidos demonstram que o BRSV pode estar presente em amostras obtidas de animais sadios, reforçando a hipótese de que infecções subclínicas fazem parte do mecanismo de manutenção do vírus nos rebanhos