Farm - 08-03-2023 - Tom Oxtoby BVSc CertCHP MRCVS - 0 comments
Semen testing and fly control


As you are all already aware, the quality of your bull or bull semen has a major impact on the fertility performance of your herd. For many years we have collected semen from bulls to analyse the quality of what they produce and looked at defrosted semen out of the AI tank to check they are still alive and swimming! Our ability to do this has recently taken a massive step forwards with the purchase of a Dynescan machine.

An award-winning piece of British technology, the Dynescan machine allows us a new level of semen analysis, especially in terms of AI straw quality assurance. We are now able to stress test semen over a two hour period, getting incredibly accurate figures for the average speed of the sperm and for the percentage of sperm that are properly motile within the straw.

When AI straws are prepared by the genetics companies, they have incredibly rigorous quality control to ensure what leaves the lab is up to their high standards. However, before this semen makes it into a cow it is transported, handled and stored in various different ways. At any point of this supply chain, something could go wrong that degrades the quality. Flasks can split, deliveries of nitrogen can get delayed, lids can be left open, straws can get dropped or handled incorrectly to name but a few of the things that we encounter. If this happens with a large batch of straws, the effect on conception rate and hence pregnancy rate can be extremely damaging, with all the associated financial costs of poor fertility.

The George Farm Vets can now offer semen testing that allows us to check straw quality. Ideally this would be done on new batches of semen before they are used to prevent issues arising. However, it can also be done to help investigate possible reasons for poor performance in a particular bull, following known or suspected storage or handling issues and even to check the viability of straws you have found floating in the bottom of the tank that are many years old! We can collect straws from the farm in our transport flask when we are on a visit, take it back to the practice and have a result within 24 hours. If you are interested in using this service, give us a call and we can arrange it with you.

We can now accurately measure percentage motility and the mean speed of spermatozoa over time, allowing you to make informed decisions on farm to increase conception rates 


Get ahead with Fly Control

Did you know that 85% of the fly population on farm are the pupae/maggots?  - so what we see is only 15% of the problem. A cow with approximately 20 flies on her legs, was shown in a study, to correlate to a 15% decrease in yield. The more flies the greater the drop in yield. USA study showed calf weaning weights on average were 5-10kg heavier on farms where flies were controlled compared to farms doing no fly control. 

Nuisance and biting flies can be a big problem in the summer and fly control is easily forgotten about until we see hoards of them bothering the cows. As well as irritating cattle, they can cause summer mastitis, infectious keratoconjunctivitis/pink eye, reduced feed intakes and growth rates.
The best way to control flies is to start early before the fly population escalates.

Chemical control - pyrethroid based pour on / spot on products or ear tags. Ear tags can be a good option if you tend see lots of eye infections or are grazing cattle away from the farm. Plus they can have less toxic effects on the environment and invertebrates compared to spot / pour on products.

Mechanical control - muck / slurry management is key to reduce the amount of possible fly breeding sites as any mucky moist heavy conditions will allow them to thrive; including areas the scraper can't reach (e.g. corners, under troughs), calf hutches and manure storage areas.

Biological control - "friendly flies" are native wasps which will lay their eggs in the pupae of developing flies, so they feed on the dead fly larvae and develop into adult wasps. Each female wasp can parasitize up to 350 fly pupae per day, hence this targets the 85% of the fly population we can't control with pour / spot on products (as these are only effective on adult flies).

A vet tech can come onto farm to assess how many bags of flies eggs you need and where, then they can distribute these fortnightly from around March to November to build up & maintain the "friendly fly" population on your farm. Flies have a short lifespan, taking < 2 weeks to go from egg to adult fly, compared to the wasps which can take up to 4 weeks. So for every one adult wasp's lifecycle, there will be two adult flies - this is why fly populations can exponentially rise and it's important to start control early.

We're currently in our second year of doing friendly flies as a practice and many farms using them are already seeing a difference. It can take a couple of years of using "friendly flies" for them to establish which is why in the initial years you may still need to use some fly products. But a study conducted in Argentina found farms using "friendly flies" saw a 90% reduction in fly populations compared to untreated farms. Overall helping to reduce chemical fly control - better for your wallet and the environment! 

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