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Getting to grips with technical issues...

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01 January 2014, at 12:00am

Richard Gard concludes his reports from the 2013 congress of the British Cattle Veterinary Association

THE opening technical paper at BCVA Congress 2013 addressed the difficult topic of production and fertility in dairy cows.

Stephen Le Blanc of the Ontario Veterinary College supported the proposal that high productivity and good fertility are not antagonistic if good management is applied.

The role for automated activity systems is important and within the USA/Canada programmes automated heat detection can provide a herd performance that is “as least as good as with synchronised-based management”. The use of pedometers is expected to reduce the frequency of hormone synchronisation injections.

Research has highlighted a multi- factorial relationship between production and reproduction and these vary between herds and between cows within a herd.

Delivering high production, good reproduction and cattle well-being is a challenge with increasingly large and productive herds, but providing for the nutritional and behavioural needs of cows is achievable.

Studies of standing time to be mounted indicate that higher producing cows stand for 22 seconds whereas lower producers stand for 28 seconds. Both situations represent a major challenge for oestrus detection.

Various research groups worldwide have shown an improvement in pregnancy when yields increased. The speaker indicates in the proceedings that this association “should not be surprising if good nutrition, cow comfort and attentive management provide the conditions for high production and good productive performance”.

He recognised, however, that “questions about whether metabolic demands for production and reproduction are reaching a biological limit and whether genetic selection criteria are optimised are important and warrant valid, large scale studies”. The factors that influence automated activity monitoring systems, the relative performance between herds and optimising performance within a herd, remain to be clarified.

George Mann of the University of Nottingham discussed the role of progesterone and embryo survival in the dairy cow. Although inadequate luteal support of early embryonic development remains an important cause of embryo mortality, current scientific evidence does not support milk yield as causal. 

Direct progesterone supplementation and the enhancement of endogenous progesterone production, through gonadotrophic stimulation, can improve pregnancy rates but results are inconsistent. Careful attention to the timing of therapy is advised.

Low progesterone is an inherent problem with individual animals and studies indicated that 68% of cows within a herd have good progesterone, 21% lower and 10% poor with levels too low for pregnancy. Progesterone given 3-5 days following insemination has shown a 10% improvement in embryo survival, but not all studies have reported a benefit.

Similarly, human chorionic gonadotrophin treatment on day 5 has been shown to increase pregnancy, but not in all cases. Cows with other health problems, such as BVD, have been shown to benefit from progesterone therapy. Metabolic issues are not strongly correlated with low progesterone.

Promoting the use of milk samples to detect pregnancy, National Milk Records launched the use of an ELISA for Pregnancy Associated Glycoproteins (PAG) in July 2013. From day 35 after service, a PAG level of less than 0.1 indicates not pregnant, from 0.1 to 0.25 is inconclusive and above 0.25 indicates pregnancy.

The same milk samples that are collected at the monthly milk recording are transported to the central laboratory. The test is used to indicate early pregnancy, followed by veterinary PD, or at 90 days to confirm that the cow is in calf. Inconclusive tests are re-tested at no charge.

Some 650 herds are currently utilising the test facility. Good on-farm records and veterinary involvement are indicated. Further information via www.nmr.co.uk.

Schmallenberg update 

An update on Schmallenberg disease, which has propelled the town in Germany to international fame, was detailed by Jules Minke of Merial Animal Health. Following the malformations in calves and lambs in 2011, with 50% milk drop in cows and 65% lamb mortality, countries have now stopped reporting cases as national reporting of cases led to an export ban.

The virus is in semen and spread by biting midges and is in the same virus group as Rift Valley Fever. Vector control, herd management and vaccination are the recognised control tools. An inactivated vaccine is now available in France and a UK licence is due. Two doses, three weeks apart, are required for cattle and one dose for sheep.

Spread of infection from herd to herd and flock to flock is very variable and there was discussion about the justification of vaccination with immune animals. The difficulty is that the infection could arise again and threaten a naive population of animals. Monitoring any clinical incidence and surveillance by veterinary surgeons remains the first alert and this awareness will direct a risk assessment for the benefit of clients.

Lessons learned

Learning the lessons from other experiences of BVDv was strongly highlighted by Klaus Doll of the University of Gleissen. The sequence of an outbreak in Germany is that two heifers were bought into the herd and a month later the herd suffered milk drop, respiratory distress, diarrhoea and abortions. Mortality was 12%.

Calves and two cows were sold to other farms with 23 herds becoming infected, 20% mortality in dairy herds and 80% on veal units. There was continuous virus shedding for weeks. Transfer of the virus was due to cattle movements but also from cow to cow and farm to farm by vets.

Vaccination with BVDv-1 live vaccine commenced under emergency procedures but not all herds improved. The incidence of BVDv-2 has been low in Germany but the relevance of genotypes will be important in the future.

Control initiatives

Joe Brownlie reviewed relevant BVD control initiatives taking place throughout Europe and the BVD-free initiative promotion to farmers in England. Cattle Health England is seen as the way forward, food industry led, a legal framework, an executive function and concentrating on endemic diseases.

A realistic budget of some £10 million per year would enable the first role to be BVD eradication and then build in other disease control. A long-term government commitment is sought; the returns are substantial (£46 million losses) and it is important that the UK at least matches the effort of other countries. Persistently infected animals would be paid for.

A breakthrough has occurred with veterinary surgeons. Some time ago it was recognised that vets do not like the complexity of BVD, but training and application has shown that once the disease is understood it is a pleasure to work with. “No farmer has ever regretted getting rid of BVD,” Prof. Brownlie said.

Richard Booth of the RVC has investigated BVD controls and outbreaks in the UK and advises that vaccination is not enough: there has to be removal of PIs and biosecurity.

Determining the herd status requires assessment of herd screen and individual tests. Blood tests, bulk tank milk samples for Elisa or PCR and ear notch samples all have a role to play within a managed programme to search out the PIs. Antibody levels change with vaccination. The tools are in place, with farmers and vets able to have confidence that BVD can be eliminated.

Progress in Ireland

Finola McCoy spoke about the work of Animal Health Ireland. Recognising the obstacles to change on the farm, emotional distress, personal pride, installing confidence, no quick fix, small things being done right, a team approach and a science base are all aspects that are included.

Working to control BVD, mastitis, Johne’s, IBR, infertility, lameness and calf health involves farmer workshops, monthly articles, consistent information, technical working groups and up to date research.

The initiative is a not-for-profit public/private partnership with time given for free by industry. Over 1,000 farmers were involved in 2013. There is much to be learned from this model of activity and enthusiasm for success.

Equally enthusiastic was the presentation from Bryony Kendall and Andrew Henderson of Tynedale Farm Vets about dairying in the dust in Mozambique. This project involving XL Vets’ members aims to provide financial and nutritional security for families by managing a jersey heifer to pro- duction. Local obstacles are great but veterinary input is helping to achieve significant results.