With the global demand for lamb increasing by a potential two and a half million tonnes by 2020, UK sheep farmers have to be in a position to take a share of this opportunity. Targeting ewe fertility to ensure a consistent lamb crop could help with this.
Why improve flock
1 Improved profitability
By using techniques to advance the breeding season, some farms have been able to overcome fluctuations in lamb prices due to supply and demand improving cash flow and profitability. An earlier lambing time provides an opportunity to utilise spring grass efficiently for lamb production allowing for earlier marketing of the lambs for a faster return on investment. Lambs sold in April and May generate on average a 21% greater return over those sold in the summer months, giving up to an extra £18 per 45kg lamb.
2 Reduced labour
Synchronisation of a lambing period also has obvious advantages as a result of the production of even batch of lambs for rearing and reduced labour. On-farm labour is one of the biggest fixed costs in a sheep enterprise and the most profitable UK producers have half the labour costs per ewe due, in part, to a condensed lambing period.
3 Improvement of the flock’s genetic potential
Synchronisation also enables the use of advanced breeding techniques such as artificial insemination and embryo transfer. These techniques can lead to fast improvements in the genetic potential of a flock and the lambs. Allowing access to superior rams without the initial purchase costs, a top terminal sire can add £3.50 extra sale value per lamb per year.
What options are there?
There are several methods which can be used to alter the breeding season of sheep, which have varying levels of success.
1 The “teaser” or
This is where the sheep have not had sight or smell of a male for a period of four to six weeks. A male is then introduced and the pheromones can bring the sheep into season a few weeks earlier than normal and there will be a small degree of synchronisation depending on where the sheep were in their normal hormonal cycle. The male introduced has to be vasectomised by a veterinary surgeon.
2 Melatonin implants
These simulate the natural decrease in day length and therefore can advance the breeding season. The implants will tend to induce cycling 60 – 70 days after their use and must be given to the males too, in order to increase the quantity and quality of the semen. They will not, however, synchronise oestrus, so the use of advanced breeding techniques and the potential for reduced labour is not possible.
3 Injections of prostaglandin (PG)
PG acts by removing the progesterone influence of the corpus luteum, allowing the levels of oestrogen to build and the sheep to ovulate if they have a follicle ready for ovulation. This method will allow for some degree of synchronisation of oestrus and ovulation, but will not advance the breeding season due to the need for the sheep to be cycling at the time of injection.
4 Progesterone devices, such as CIDR® OVIS
These mimic the natural progesterone of the sheep and in essence hold the cycle and allow the development of follicles that are ready for ovulation. When the device is removed the drop in progesterone allows for oestrus behaviour and the timed injection of equine chorionic gonadotrophin (eCG) means the developed follicles will ovulate leading to close synchronisation. The use of these devices in this manner also allows the commencement of cycling out-with the normal breeding season, by triggering natural hormonal events. Hence progesterone devices can both advance and synchronise the breeding season.
Why CIDR OVIS?
In European studies in several different breeds of sheep, CIDR OVIS has been shown to be highly effective at stimulating and synchronising oestrus behaviour in ewes at different stages of seasonal breeding.
Another European study has shown that all ewes ovulated within 58 hours after removal of CIDR OVIS and administration of eCG. In instances where oestrus is synchronised, knowledge of the point of ovulation can help determine the most successful time for AI and other advanced breeding methods.
CIDR OVIS had less removal issues (P<0.05) than a fluorogestone acetate sponge and 84.5% of sheep showed no or a clear discharge when using CIDR OVIS.
For further information on how CIDR OVIS can benefit your flock and improve your productivity speak to your veterinary surgeon.