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This paper presents puppy mortality and postmortem findings for a birth cohort of boxer puppies born in the Netherlands between January 1994 and March 1995. In all, 457 litters were registered, of which 414 (90.6 per cent) were involved in the study. The 414 litters contained 2629 puppies, a mean litter size of 6.4 puppies. Of the 2629 puppies 571 (21.7 per cent) died or were euthanased before they were weaned at 50 days of age; there were 147 (25.7 per cent) stillbirths; 102 (17.9 per cent) were euthanased because they were white; 269 (47.1 per cent) of the puppies died during the first 21 days of life and 53 (9.3 per cent) puppies died between days 22 and 50. The cause of death or the reason for euthanasia was assessed by either the breeder or the veterinarian in 176 of these 269 puppies but was not determined in the other 93 puppies. Three hundred and two puppies were examined postmortem; the most important cause of death or reasons for euthanasia were inflammatory disorders (102; 33.8 per cent), non-inflammatory disorders such as asphyxia and malnutrition (66; 21.9 per cent), euthanasia because they were white (51; 16.9 per cent), and congenital abnormalities (45; 14.9 per cent). No cause of death or reason for euthanasia could be found for 38 puppies (12.6 percent)

The field trials of drug and vaccine efficacy published in The Veterinary Record in the last five years were reviewed. The reviewers showed that in addition to some excellent studies with clear and concise design and analysis, there was a considerable lack of detail in reporting the method of allocation of animals to treatments, whether groups of animals or individual animals were allocated to treatments, whether the trials were blind, and a lack of formal analysis of the results. A considerable number of studies had problems with clustering of data. Some critical features of the design and analysis of a clinical field trial are discussed and improvements are proposed.

Ten herds with low somatic cell counts in bulk milk had an incidence of clinical mastitis of only 2.2 per 100 cows whereas 10 other herds with similarly low cell counts had an incidence of 53.6 per 100 cows. The major pathogens in the herds with a high incidence were Escherichia coli, Streptococcus uberis, Staphylococcus aureus and the coagulase-negative staphylococci. The percentage of uninfected quarters in the herds with a high incidence of clinical mastitis was 21.4 per cent compared with 12.2 per cent in the herds with a low incidence of clinical mastitis. The prevalence of coagulase-negative staphylococci, Corynebacterium bovis and Micrococcus species was higher in the herds with a low incidence of clinical mastitis. There was a significant linear relationship between the percentage of uninfected quarters and the incidence of clinical mastitis in the herds with a high incidence of clinical mastitis. In herds with a low incidence of clinical mastitis significantly less teat disinfection after milking was practised. The results suggest that infections with minor pathogens tend to protect cows against mastitis, and that teat disinfection after milking may increase the percentage of uninfected quarters and lead to an increased risk of clinical mastitis in herds with low somatic cell counts in bulk milk.

A total of 1140 clinical cases of mastitis, with at least one inflamed quarter, were reported on 125 farms with somatic cell counts in bulk milk less than 150,000/ml. The average annual incidence was 17.9 cases per 100 cows and ranged from none to 80 cases per 100 cows. The microorganisms most frequently isolated were Escherichia coli (16.2 per cent), coagulase negative staphylococci (13.0 per cent), Staphylococcus aureus (9.6 per cent) and Streptococcus uberis (8.0 per cent). Only two cases of Streptococcus agalactiae were found. As the incidence of clinical mastitis increased, the proportion of S aureus also increased, while the proportions of E coli, S uberis and Streptococcus dysgalactiae remained about the same. Most of the clinical cases of mastitis occurred in early lactation, in November, December and January. However, after correction for the number of calvings per month, the incidence of mastitis was highest in the early summer months.