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Flashcards in CAL: Bovine Reproduction Deck (19)
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  • Key Performance Indicators on a Farm

Submission Rate in Dairy cattle

  • submission rate is the proportion of eligible cows which are served in a given period.
  • A realistic targetsubmission rate for an all the year around calving herd is greater than 75%

Thus, submission rates are relatively high, but conception/pregnancy rates are low on this farm.

What areas might you focus on to investigate this type of problem? Try to rank them in order of importance

  • AI technique (Who is doing the AI? Does the decrease in fertility coincide with a new operator? How well trained are they? What technique are they using - AM/PM rule? Another method?)
  • Heat detection (submission rates are high, so this is less likely, but if the wrong animals are being selected for service, then submission rates would remain high whilst conception rates are low. This may also be linked to AI technique/operator)
  • Nutrition (cows in Negative Energy Balance with low BCS at/post calving may encounter significant problems getting back in calf. Cyclicity may also be an issue that is detected here?)
  • Infectious diseases (list the ones that cause low conception rates)
  • Investigate bull fertility if used (This farm appears to be using AI, but if a bull is used, you may find that his fertility may affect specific groups within which he is used - i.e. on a dairy farm, the bull is most likely to run with the heifers, therefore any infertility may be most noticeable in these groups)

Gestation of Dairy Cow

  • 275-276 days


  • Whist the regulations have changed in recent years, there is still the requirement to inform AHPA (should be done by the farmer but probably worthwhile reminding the farmer of this) of any cattle abortion
  • This consists of any calf born prior to day 271 of a normal gestation or prior to day 265 of embryo transfer.
  • Brucellosis testing will only be initiated if animal is not contributing to milk tank e.g. beef, heifer or if it is an imported animal (or sudden outbreaks of abortions).
  • Bulk tank samples are regularly and routinely tested for
  • Brucellosis therefore if the animal that aborted was contributing to the bulk tank milk, this would have been detected by the routine surveillance
  • It is important that brucellosis testing in those aborted foetuses is kept up as England is required to consistently “prove” that brucellosis free by testing of abortions. The following is the text that AHPA routinely send out to local farm veterinarians

List four infectious causes of poor fertility taking into account that the recent abortion may or may not be linked to the current situation

  • IBR - Infectious Bovine Rhinotracheitis
  • BVDV - Bovine Viral Diarrhoea Virus
  • Neospora Caninum
  • Leptospirosis

Of these four, which is most likely to account for abortions but unlikely to be a major cause of early embryonic death?

  • Neospora Caninum
  • coccidian parasite of animals

Neospora Caninum

  • Neospora caninum is the most commonly diagnosed cause of abortion in the UK. The organism is a protozoan parasite. Dogs are the definitive hosts of Neospora caninum and cattle are intermediate hosts that can become infected either
  • Vertically – i.e. a calf born to a congenitally infected dam or;
  • Horizontally – this occurs through ingestion of faeces from infected dogs contaminating feed or grazing pasture.
  • Farm dogs may become infected by ingestion of placental material or dead calves from infected animals and can act to spread the disease further on a farm.

Abortion by Neospora

  • Abortion may occur through transplacental infection of the foetus and is generally observed between months three and eight of gestation, hence may not account for return to service seen before 90 days gestation in this case.
  • A blood sample to be tested for antibodies from the animal that aborted should be sufficient to determine if the abortion was due to neospora in this case.

Lepto, IBR and BVD with abortion


With respect to abortion:

  • Lepto most often causes late term abortions from month five to term
  • IBR may cause abortion throughout gestation
  • BVD tends to cause early returns to service and abortion up to 6 months of gestation.

Clinical signs you would expect to see for IBR beyond abortions and infertility

  • Acute Upper Respiratory Infection - one of the common clinical signs associated with acute IBR infections
  • Fatal pneumonia - may occur with acute IBR infection although this may be considered rare in most circumstances
  • Decreased milk yield is a common clinical sign and will accompany the pyrexia and loss of appetite
  • Abortion is the primary effect seen on calves born to IBR positive dams
  • Vaginitis may be seen with some forms of bovine herpes viruses and so may be associated with IBR infection, although will often go unnoticed
  • Conjunctivitis is a common feature of IBR infection - especially the acute primary outbreaks. Ocular discharge is often also noted as a result
  • Nasal Discharge is commonly noted with IBR infection. It is initially serous and later muco-serous to muco-purulent
  • Secondary diseaes is not common, but secondary pathogens may invade damaged lung tissue as a result of the initial outbreak, thus more severe pneumonias may be seen
  • Pyrexia can be severe with IBR infection and temperatures may reach 42C

clinical signs you would expect to see for Lepto beyond abortions and infertility

  • often mild and unnoticed - many lepto infections in cattle are subclinical and will go unnoticed. This is especially true if the animal is not pregnant or lactating
  • In addition to abortion, weak calves may be born to dams infected with leptospirosis
  • Agalactia and decreased milk yield may be apparent with acute Lepto infection. However, this may often be mild and go unnoticed
  • Flaccid udder is a clinical sign that may be associated with lepto infection in lactating cattle
  • bacteria has the potential to reside in the kidney and result in animals that may intermittently shed in the urine, UTI is not a feature of lepto infection
  • Chronically infected animals may be treated with long acting oxytetracycline or long release ceftiofur yet, whilst these two drugs have been shown to be most effective against the disease, clearance is not certain following treatment

Presentation of IBR

  • IBR can be mild. Especially if it is the second time the animal has experienced the infection.
  • Usually primary outbreaks are most severe and this is when severe respiratory signs, pyrexia and abortion are most likely to occur.
  • Once infected, and as with all herpes viruses, animals become latently infected (tri-geminal ganglia) and the virus may recrudesce under periods of stress.
  • Secondary outbreaks as a result of recrudescence are generally mild and abortion is not commonly seen with secondary outbreaks

clinical signs you would expect to see for BVD beyond abortions and infertility

(Bovine Viral Diarrhoea Virus)

  • Decreased milk yield is a common clinical sign and will accompany the pyrexia and loss of appetite. This may go unnoticed by the farmer in many situations though
  • As well as abortions, still births and weak calves can be a result of BVD infection in the dam
  • High Levels of Concurrent Disease - BVDV is immunosuppressive and as such, it makes other diseases more likely and also more severe. These secondary diseases can range from infectious causes of lameness, mastitis, pneumonia and scours. They are often unnoticed in adults, but BVD may be a major cause of severe secondary pneumonias and scours in calf groups.
  • Mild respiratory infection can be noticed with acute BVD infection but, in combination with the immunosuppression the virus causes, this may facilitate secondary pathogens to invaded the lung and resulted in a severe pneumonia
  • Conjunctivitis is not a common clinical sign to occur following BVD infection, but this may accompany the mild respiratory disease that the virus causes in some cases
  • Despite its name, diarrhoea is one of the least common clinical signs of BVD infection!
  • BVD most often only causes mild pyrexia. This may, in most cases, go unnoticed.

With BVDV, How are PI animals created?

  • In utero infection in the first trimester of pregnancy leading to the birth of an immunotolerant calf
  • 0 to 110 days of the pregnancy

PI calf and the “Trojan Cow”


The farmer asks how many PIs are commonly found in infected herds and you reply

  • 1-2%

Eradicating BVDV from farms and searching for PI’s

  • vaccinating and biosecurity are huge in prevention!
  • Also need to cull any PI animals