The incidence of clinical respiratory disease in 698 young beef bulls kept in 68 pens, and their exposure to respiratory pathogens after their arrival at 51 fattening operations in western France were assessed. Antibodies against bovine respiratory syncytial virus (BRSV), bovine herpesvirus type 1 (BHV‐1), Mannheimia haemolytica and Mycoplasma bovis were measured by ELISA. The incidence risk of respiratory disease was 18.5 per cent during the first six weeks. Cases occurred in 37 of the 68 pens, and in these pens 30.9 per cent of the bulls were affected. Their exposure to BHV‐1 was very limited. When they arrived a high proportion of the bulls were seropositive to M haemolytica and a high proportion seroconverted to BRSV, M haemolytica and M bovis within the first six weeks. The risk of incidence of respiratory disease was lower in the pens in which the bulls had been vaccinated against M haemolytica . Higher proportions of the bulls were affected in pens in which small proportions of the bulls were seropositive to M haemolytica or BRSV on arrival, and in pens in which high proportions of the bulls were exposed to M haemolytica or BRSV during the first six weeks.

Milk samples from 135 herds in Brittany were tested by a blocking ELISA for antibodies to bovine viral diarrhoea virus (BvDv) and used to assess the relationship between the bulk milk result and the within‐herd prevalence of antibody‐positive lactating cows. This relationship was first quantified by using a general linear model and controlling for the number of cows contributing milk to the bulk tank, for the percentage of primiparous cows in the herds and for the number of milkings contributing to the bulk tank. Receiver operating characteristic (ROC) analysis was then used to define classes of percentage inhibition in the bulk milk associated with minimum intraclass and maximum between‐class variances of the within‐herd prevalence. Only the percentage inhibition of bulk milk had a significant positive effect on within‐herd prevalence (R ² =0.85). The ROc analysis provided three classes of bulk milk results corresponding to different expected levels of within‐herd prevalence. Herds with bulk milk percentage inhibitions of 0 to 35 per cent, 35 to 60 per cent and 60 to 100 per cent had mean (sd) observed prevalences of 4.8 (5.7) per cent, 21.6 (14.6) per cent and 66.0 (29.3) per cent, respectively. Herds with a bulk milk inhibition of 0 to 35 per cent were expected to be BVDV‐free. A herd with two consecutive bulk milk results four months apart of 60 per cent or more was likely to have a very high prevalence (median of 93 per cent) and could be suspected of harbouring an active infection.

SUMMARY: Type D bovine botulism outbreaks associated with poultry litter are increasingly reported in European countries, but the circumstances of exposure toClostridium botulinumtoxins remain unclear. In spring 2015, a large type D/C bovine botulism outbreak affected a farm with dairy and poultry operations. Epidemiological and laboratory investigations strongly suggest that the outbreak was caused by feeding cattle with insufficiently acidified grass silage that was contaminated by type D/CC. botulinumspores. The source of the spores remains unclear, but could have been a stack of poultry litter stored in the grass silage pasture before harvesting. The presence of putrefied poultry carcasses mixed in with the litter is relatively unlikely considering the careful daily removal of poultry carcasses. These findings reinforce the importance of proper ensiling of feed materials and highlight the need for safe disposal of poultry litter, even in the case of good management of poultry deadstock, in order to prevent bovine botulism.