Neo Natal Calf Study

Samples taken from calves on about 1% of NZ dairy farms have shown the relative importance of five organisms that cause scouring in young calves. Rotavirus and Cryptosporidium cause the most infections, Coronavirus may also be important, E. coli K99 is a minor problem, and Salmonella seems to be rare among dairy calves.

Neonatal calf diarrhoea results in considerable economic loss to dairy farmers and the dairy beef industry in terms of calf death, poor growth and high treatment costs. Scouring is hard to avoid given the presence of infectious organisms and the difficulty in providing ideal animal husbandry at calving, the busiest time of the dairy farming year.

Overseas studies have shown that there are five main infectious agents involved in calf diarrhoea – Bovine Rotavirus, Coronavirus, enterotoxigenic Escherichia coli (k99), Salmonella and Cryptosporidium parvum. Although these organisms are present in New Zealand there were few data on how prevalent they are and their relative impact on animal health. There was also little information on farm practices for the prevention and treatment of calf diarrhoea in New Zealand.

PhD student Julanda Hamad Al Mawly has carried out an epidemiological study of neonatal calf diarrhoea on dairy farms. The results indicate the relative importance of the infectious organisms and how effective vaccination, drugs and farm management practices are, and how they can be improved.

The study was carried out with the support of an animal health company. Farms were chosen at random from the seven main dairying regions, and company staff collected faecal samples towards the end of calving from 96 dairy farms. In the case of E. coli calves 1 – 4 days old were sampled, and for the other organisms calves needed to be between 9 and 20 days old. Information about past and present calf deaths, vaccination history and calf rearing practices was also gathered from these farms.

The samples were sent to IVABS for identification, which involved molecular characterisation of the isolates to see what genotypes were present. Results were as follows :

• Calf scours were observed in more than 50% of the farms sampled.

• Rotavirus – found on more than 70% of farms

• Cryptosporidium – on 68% of farms

• Coronavirus – on 47% of farms (provisional result)

• E. coli K99 – on 11% of farms

• Salmonella – very rare

• Two or more infections – more than half of farms

• There is a decline in Rotavirus in faeces on farms where cows are vaccinated.

The results indicate Rotavirus and Cryptosporidium are widespread among newborn calves and that vaccination against Rotavirus helps in reducing this agent’s prevalence on farms.