Newcomers must not underestimate the importance of careful pre- and post-insemination management of ewes.
That’s the advice of Cumbria vet Andrew Hambleton of Paragon Veterinary Group, who says flocks embarking upon AI for the first time must set out a strict plan of routine flock managements tasks well ahead of the start of the AI programme.
Read advice on the advantages of using AI, how best to select ewes, timing and semen collection.
Selection of AI candidates
Dosing or foot-trimming or giving any other treatments must be done [in advance] so that ewes have to settle, which means that planning well ahead is crucial.
Choosing the correct animals is also key to the programme’s success.
“It’s also important to be strict about the ewes being selected for AI and to focus on those that have had a healthy, trouble-free breeding history. Any ewes that have suffered health issues, difficult lambings or bad feet should not be included,” advises Mr Hambleton.
Body condition scoring should be carried out as an initial assessment.
Ewes need to be in body condition score 2.5 to 3 when inseminated so it’s important to allow enough time for any changes to be made to grazing regimes to improve the condition of thinner ewes, advises Mr Hambleton.
Assessing the body condition of ewes bound for an AI programme needs to be done once lambs have been weaned, he adds.
See also: Tips for a Successful Breeding Season
But as well as making sure ewes are in the right condition once lambs have been taken off, this is the best time to do an all-round health check and to identify any ewes needing foot treatments.Mr Hambleton
Assessing trace element profiles by blood sampling a random batch of the ewes is also very important as any deficiencies could adversely impact conception rates.
“It’s worthwhile speaking to your vet and to taking blood samples from a random selection of ewes from the AI group. The mineral status of ewes is critical and must be checked early. If a bolus treatment is necessary it needs to happen six to eight weeks ahead of the AI date.
Selenium and cobalt, as well as vitamin E deficiencies, are the most critical in terms of fertility.
The aim should be to collect blood samples from a range of different ewes within your prospective AI group, says Mr Hambleton.
Producers should also discuss any risks associated with toxoplasma or enzootic abortion with their vet and ensure all relevant vaccinations are given at least four weeks ahead of insemination.
For four to six weeks prior to tupping, ewes should be kept on good grazing and perhaps fed a small amount of a high energy feed such as sugar beet – although that depends on the number of ewes in the programme.
“But avoid grazing ewes on swards that are high red clover to avoid raising oestrogen intake levels.
“Once all the necessary routine treatments have been carried out ewes should be left alone for at least four to six weeks before the AI programme starts. The next time they are gathered it will be for sponges to be inserted to begin the synchronisation programme.”
Working backwards from the selected lambing date, sponges should be inserted 14 days ahead of the actual date of insemination, explains Mr Hambleton.
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- Sheep breeding and fertility
Sponges are removed after 12 days and the ewes are injected with Pregnant Mares Serum (pmsg). On day 14, the ewes are inseminated.
Which type of semen you use should also be considered as this can affect how many rams you must use.
“The majority of the semen we use is fresh or frozen but most will be fresh. When it’s fresh it allows a flock owner to use a ram over a much larger number of ewes – say 100 ewes or more rather than 30-50 it would cover in a day by natural service.”
The cost of AI
The cost of AI can be between £10-£20 a ewe, but this can vary from flock to flock as costs are based on a “tiered” system that is dependent upon the number of ewes in the programme. And then there is the added cost of the semen collection.
“Some tups will provide enough semen from one collection to use on 100 ewes whereas others may need up to seven or eight collections, so it’s not easy being specific on total costs.”
The advantages of AI
One of the biggest advantages of AI is being able to use superior genetics across a larger proportion of the flock. However, labour requirements need to be considered too.
“More labour is needed at lambing [although] those costs are concentrated over a short time.”
Average conception rates of 70-80% can be expected when using fresh semen although success hinges on ewe selection.
“There is no significant correlation between ewe age and rates of conception, but clearly the older a ewe the more likely she is to have had some issues – say a difficult lambing – that may have been forgotten about but which may affect her current level of fertility.”
See also: When to Separate Ram Lambs from Ewes
Semen collection – considerations
Semen can be collected from most tups three or four times to provide a day’s insemination needs but it’s important to have a semen check undertaken in advance of the AI date.
“Don’t take risks and assume a tup is fertile. Take a semen sample about two to four weeks prior to collection – even though a tup may have been a successful sire previously. It’s not unheard of for a tup to have picked up an infection over the summer that can affect its fertility.
“And remember too that some tups can be ‘shy’ about having semen collected so it’s worthwhile making sure all tups are used to having people around them before the collection day.
“And always have a back-up. While it may be that there is one particular tup that is being relied upon as the principal sire, it’s essential to have several tups available just in case,” Article Source Farmers Weekly