The Itinerant Bull SGTR case Flashcards
Read this background slide first and then all other FC are quesitons relating to this history of the farm
(saves having every FC hundreds of words long)
Try to do in order as works a long as a case
Mr Plum has a herd of 200 HF cows most of which calve in the autumn with about 50 stragglers calving between January and April. The herd is on a TMR with a 305 day yield average of 10,234 litres of milk/cow/year.
All of the cows are artificially inseminated by Mr Plum and his son James. This year the submission rate has been 30% and the conception rate 31%; by the end of March 80 cows are still not in calf.
Some definitions:
Submission rate: the percentage of cows served of those available for service in a given time period. The target value for submission rate is a year round calving herd is around 65%, investigation is indicated when submission rate drops below 40%. In a truly seasonal calving herd the submission rate needs to be much higher (>85%) to maintain a 6-8 week calving period.
Conception rate: the percentage of cows pregnant for all services. Pregnancy rate appears a more accurate description of this outcome as many cows conceive after service but will lose an embryo early on and return to oestrus at the normal time in their cycle. However, most people also use pregnancy rate to mean different things. The expected value for conception rate is 40% (top 5% of UK dairy herds have a conception rate >50%). Active investigation is instigated when the conception rate drops below 30%.
Is the submission/conception rate acceptable?
Submission rate and conception rate are too low.
Give 5 factors that can effect submission/conception rates?
The factors that affect submission rate are herdsman skills, the time taken to look for cows in oestrus, use of heat detection aids and lameness, environment, pecking order, nutritional factors and health of the cows.
What questions would you ask the farmer to further investigate the fertility performance?
- Conception rate is multifactorial with almost every aspect of management, nutrition, infectious disease and general health contributing in a positive or negative way.
- Fertility history i.e. conception rate over the past years
- AI technique
- Management and nutrition; what is he feeding, how is he managing transition/early lactation cows, BCS in dry/early/midlaction cows.
- Any concurrent metabolic diseases (milk fever, ketosis, LDAs etc)
- Infectious disease status, is he aware of diseases present on the farm, is there any historical diagnostic
Mr Plum decided to bring in a sweeper bull to get his barren cows pregnant. He did not want to risk a young bull so he has borrowed a proven bull from Mr Jones (his brother-in-law) that had been in use in his suckler herd. Mr Plum left the bull with the cows for 2 months and 1 month later you are asked to PD them all.
Fertility Visit Results
- PD+ve = 6 (all 30-40 days in calf)
- PD-ve = 74 (70 appear to be cycling normally)
- Ovarian abnormalities = 2 with follicular cysts
- Uterine abnormalities = 2 with mild endometritis
- Other = 7 lame cows
- What is the pregnancy rate?
- Discuss the results from the visit and broadly list areas/different diagnoses that could contribute to the poor fertility performance –
- 6 PD+ cows / 80 eligible cows = 7.5%
- The majority of cows appear to be cycling normally (no true anoestrus), two cows with cysts or endo-metritis are not unusual in a high yielding dairy herd, the same applies to 7 lame cows; it is not what we’d like to see but it does not explain the fertility issues observed.
Oestrus detection management (farmer does not see it or cows don’t show it)
Nutrition (quality, quantity, palatability) leading to negative energy balance in a high yielding herd
Concurrent metabolic diseases (endometritis, ketosis)
Infertility or inability of the bull (semen quality, lameness)
Infectious causes.
Choose the most suitable additions/options Mr Plum could now include to try to improve the submission rate for this herd
- Heat detection systems
- Use a sweeper bull earlier in the block calving
- Using a sweeper bull later in the calving
- Check for endemic diseases
- Synchronise females
- Include GnRH at day 0 and day 10 post service
- AI refresher course
- Heat detection systems – CORRECT – pedometers, kamars, tail paint
- Use a sweeper bull earlier in the block calving - CORRECT
- Using a sweeper bull later in the calving – INCORRECT
- Check for endemic diseases – correct – lameness might be having an effect.
- Synchronise females – CORRECT – although this might be an expensive option, due to cost per cow.
- Include GnRH at day 0 and day 10 post service – CORRECT - Could improve pregnancy rate
- AI refresher course – this would improve conception rate but not submission rate
Mr Plums brother in-law is now on the phone
Ring ring. Mr Plum brother-in-law, Mr Jones, phones you. Mr Jones has 80 suckler cows. He used to have 50 but expanded his herd this year by buying in 30 cows from 4 different farms. His farm utilises some low hill pasture. He also keeps 600 ewes.
He has talked to Mr Plum about the problems in his herd who hinted that Brian the bull may be a problem. Mr Jones is now concerned about his bulls’ performance and wants you to PD his cows and check the bull.
Pregnancy diagnosis results
You PD the 30 cows and only 19 are in calf. The bull is an 8yr old Limousin that has performed very well for the last 3 years, and his semen sample last year was fine.
Physical exam of the Brian the Bull
- Normal physical exam
- Normal rectal exam
- Scrotum 36cm circumference (…is this normal?)
One of the cows is bulling so you put the bull in with her. He serves the cow without difficulty and no penile defects are noted.
List 2 investigations/diagnostic tests you would like to consider to determine where the issue is with the poor fertility performance?
Check that scrotal circumference is WNL (what is normal for an adult Limousin bull?)
Collect a semen sample using electro-ejaculation, manual massage or artificial vagina.
Check bull to cow ratio: As a general rule up to 25-30 cows/heifers should be assigned to a yearling bull with up to 45-50 cows/heifers to an adult bull.
Check for infectious disease affecting fertility
Fresh semen sample microscopy
You decide to take a fresh semen sample from Brian the bull. You could compare this with last years sample results to check for any deterioration.
You collect a semen sample into a warmed tube, and examine the sample immediately on farm. The sample is cream coloured and homogenous. You’ve remembered to bring saline and eosin nigrosin stain.
Under the microscope
- Under 100x magnification the sample is swirling
- Under 400x magnification you see a dense semen sample with a high proportion of live motile sperm.
- You place a cover slip on a diluted sample and then track a number of individual sperm and they show good linear motility.
- You make a smear with nigrosin eosin. You observe that less than 10% of sperm have anatomical defects
Does the bull appear to have good fertility based on this result?
Yes
You decide to take a blood sample to look for specific disease, rather than generalised haematology/biochemsitry.
What can we test for?
- IBR (antibody)
- BVD (virus/antibody)
- Johnes
- Lepto
You decide to blood test Brian and 4 non-pregnant suckler cows
You decide to check for infectious disease, as the bull could be a vector between both farms.
List 5 differentials for the infectious diseases possible
- Campylobacter fetus venerealis
- BVD
- Leptospirosis
- IBR
- Mycoplasma bovigenitalium
- Bluetongue
- Brucella abortus
- Tritrichomonas foetus
You send off a sheath wash from Brian for culture at the lab.
You can also do vaginal swabs from the cows (in a transport rich media) but it is usually more successful to sheath wash the bull with phosphate buffered saline and send to lab for bacteriology.
See the results attached
- Do we have a diagnosis yet or do we need to do more tests?
- If you think you have a diagnosis, which of these do you think the cause of the fertility is: BVD, Laptospirosis, Campylobacter, IBR?
I have a diagnosis!
Which of the following based on the previous tests have you decided is the cause of the fertility issues:
- BVD – INCORRECT - Test results indicate there is probably no BVD on the farm
- Leptospirosis - evidence of exposure; need paired serology to better interpret results, but have to be around the time of infection, which is now weeks ago; check vaccination history, as it may be in response to vaccination.
- Campylobacter infection – CORRECT - Significant infection found on bacteriology and the finding fits the clinical picture.
- IBR - Some animals tested positive on titre testing. Appears to be recent infection or could be recrudescence of IBR virus. Need to check vaccination history (be specific on vaccine used, there is a marker vaccine). The timing of paired serology does not match with the timing of fertility issues and even though IBR could produce this picture you would expect some sick animals if it was a new infection.
What is the most likely source of capylobacteria infection based on the farms history?
Probably one of the purchased suckler cows was a carrier.
Which of the following are sensible treatment options for campylobacter infection?
- Use AI for 1-2 years and no bulls
- Treat Brian with sensitive antibiotics
- Recommend Brian is culled
- Isolate any young animals and attempt treatment
- Advise on improved head detection methods
- Consider an Ovsync programme
Use AI for 1-2 years and no bulls – CORRECT. The disease is self-limiting if no bulls are present. If both herds use AI for one or preferably two years this should eliminate the infection from the herd.
Treat Brian with sensitive antibiotics – older bullers respond poorly to treatment due to prepuce becoming too convoluted and therefore antibiotics penetration is poor
Recommend Brian is culled – CORRECT - older bullers respond poorly to treatment due to prepuce becoming too convoluted
Isolate any young animals and attempt treatment – CORRECT – treatment may be attempted (streptomycin, parenteral and wash, 3 days) Advise repeated attepts to culture after treatment and before use, as it is difficult to be certain the bull is negative. Should definitely at least discuss culling with farmer and make clear the bull is reused at the farmer’s own risk
Advise on improved head detection methods - CORRECT
Consider an Ovsync programme – This would only really be beneficial after evaluating their heat detection
