Farm Ireland

Tuesday 12 December 2017

Tackling disease threat vital to cutting herd's empty cow rate

Dr Dan Ryan

At this time of year, farmers like to get a full picture of the reproductive status of their herds. Be it a suckler or dairy cow, empty cows dictate the number of replacements required for next year. Unfortunately, the empty rate on many farms visited this autumn has been more than 15pc.

High empty rates in cows can be explained by various factors including:

  • Calving difficulty;
  • Nutrition;
  • Health problems.

We can identify cows which have undergone embryo or foetal death by scanning. In addition, farmers will see cows abort pregnancies. These issues include:

  • Increasing the empty rate;
  • Reducing the opportunity to sell in-calf heifers;
  • Prompting farmers to investigate the reasons behind foetal death.

Diseases associated with loss of pregnancies include:

  • IBR;
  • BVD;
  • Leptospirosis;
  • Salmonella;
  • Neospora;
  • Johne's Disease.

The impact of any one of these diseases on overall reproductive performance can be devastating.

Animal Health Ireland is putting together an excellent programme of education to help manage and prevent an outbreak of these diseases. A lot of confusion, mis-information and poor implementation of vaccination programmes exist at farm level. You first need to identify if a risk of disease exists on your farm. Pooled milk or blood samples will identify if there has been a disease challenge in your herd. Depending on the severity of the disease challenge, a vaccination programme may be warranted.

Leptospirosis is present on more than 90pc of Irish farms. It causes both early embryonic death and is associated with abortion in cows. Most of our clients vaccinate against this disease. Symptoms of the disease include milk drop, high temperatures, irregular repeats and abortion.

BVD and IBR are currently the two most topical diseases associated with poor health and reproductive performance of cows. The symptoms of IBR include discoloured nasal discharge, milk drop, high temperature, rapid weight loss, increased incidence pneumonia and poor pregnancy rates. The symptoms of BVD include many of the above plus an increased diarrhoea incidence.

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BVD is one of the biggest threats to the prosperity of the farm. BVD depresses the immune system of the cow and allows other diseases to impact on its health. An animal persistently infected (PI) with BVD will shed the virus and cause a transitory increase in antibody levels. BVD is transferred to the foetus from the second month of pregnancy, resulting in either foetal death or the birth of a PI calf.

Management of BVD and IBR may have to include a vaccination programme. However, in the case of BVD, the PI animals have to be identified and removed from the herd. The PI animals will challenge those vaccinated and reduce its effectiveness. Many farmers forget to follow up with booster injections at the appropriate interval.

Protection from the disease will only cover a prescribed period. Vaccination programmes will not be effective if the immune system of the animal is challenged because of nutritional or environmental stressors. For example, it has been shown that if copper levels are low, the response to vaccination is poor. Blood or milk samples should be checked for mineral status prior to drying off in early and mid-lactation. A mineral supplement specific to your herd's requirements will ensure a deserved response to vaccination.

In the case of salmonella, it is now recommended to vaccinate prior to drying off the cows. The stress associated with drying off cows has been linked to an increased risk of abortion via salmonella.

Neospora causes abortion or mummification of foetuses. There is no vaccination programme available in this country. Dogs and foxes are intermediate hosts. Contamination of food with infected faeces results in death of the foetus in utero.

Prevention is the key to management of this disease, so:

  • Discard afterbirths;
  • Avoid contact of feed by dog faeces;
  • Do not breed cows diagnosed with the disease to sires destined to result in replacements.

Finally, Johne's Disease has an incubation period of 18 months prior to clinical symptoms, which include diarrhoea and excessive loss in body condition. The primary transmission route is through colostrum. Animals diagnosed with the disease should be removed from the herd. Pooled colostrums are a major risk to all calves, therefore we have to have a policy of identification and removal of carriers.

In my opinion, the cattle industry needs a mandatory health-screening programme. Such a move would maintain animal welfare, while also helping to ensure that milk and meat supplied to the food chain were protected. In addition, this strategy would improve cost-efficient food production at the farm gate. Biosecurity at farm level has to be a goal in the cattle industry, similar to the one in place for the pig production sector.

Dr Dan Ryan is a reproductive management consultant

Irish Independent