A recently published quarterly surveillance report by the Department of Agriculture shows that, as seen previously, the most common cause of bovine mortality in all cattle ages from post-mortems conducted by the regional veterinary labs was alimentary tract disease (digestive tract disease), accounting for over 40% of deaths in the second quarter of the year. This is followed closely by respiratory tract disease, accounting for almost 17% of deaths in the same period.

In terms of individual diagnosed causes, the report highlights enteritis and pneumonia as the main killers, followed closely by bacteraemia/septicaemia and enteritis and septicaemia. In terms of clostridial diseases, blackleg accounted for almost 80% of fatalities, with pulpy kidney disease accounting for over 20% of deaths from clostridia.

Calf and weanling post-mortems

For calves under one month of age, almost 55% of deaths recorded on post-mortems by the regional veterinary laboratories (RVLs) were attributed to disease of the respiratory tract. In calves from one to three months of age, post-mortems show that mortality due to digestive tract disease occurred in about 37% of cases, with death due to respiratory disease accounting for approximately 27% of deaths. In weanlings (three to 12 months) the main causes of deaths recorded were much more varied than calves, with digestive tract diseases, respiratory tract disease and neurological disease the three main causes of mortality at 22%, 19% and 13% of the total cases respectively.

Main digestive tract disease causes

The main causes of digestive tract disease recorded at post-mortems were Cryptosporidium (23%), Rotavirus (18%), E-Coli (12%) and Coccidia (7%). However, in about 28% of cases, no specific agent of infection was identified from animals which were diagnosed with enteritis or gastroenteritis.

ZST tests

The ZST test or zinc sulphate turbidity test in neonatal calves indicates the level of maternal colostral immunity which the calf has received from its mother via colostrum in the first few hours of birth. This is deemed to be very significant in determining the immune status of the calf in early life. The results of tests carried out on 424 ill or dead calves in the second quarter of the year show that 48% of these had what was deemed to be inadequate levels of immunoglobulin levels. Factors that will have the largest effect on this are the volume, quality and timing of feeding of colostrum to calves.

Mastitis and abortions

In quarter two, 545 milk samples were analysed for mastitis culture. Staphyloccus aureus accounted for about 22% of pathogens recorded, followed by Streptocuccus uberis at about 11% and Streptocuccus dysgalactiae at about 4%.

In terms of bovine abortions, 183 foetuses were submitted to the RVLs in the second quarter. Of these, 120 or about 66% were deemed to be abortions. In almost 65% of the cases there was no clear agent identified as the cause of the abortion. When submitting samples, where possible the placenta (afterbirth or cleanings) should be submitted with the calf or foetus to help in giving an accurate diagnosis. Infectious agents recorded in foetuses continue to be Coliforms, Neospora, Salmonella Dublin, Leptosira and other bacteria.

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