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- Some breeders do not want to interfere with nature and prefer to leave a ram with the ewes so that they can come into heat and breeding can proceed naturally.
- In order to synchronise a flock of ewes to come into heat at the same time, progesterone must be increased artificially using intravaginal sponges (CIDRs) that release progesterone.
- Assisted by the synchronising agents, all ewes reach oestrus simultaneously, facilitating planning and shortening the lambing period.
- Lambs are the same age, which simplifies weaning, and a large group of lambs will be market ready simultaneously.
- Synchronising ewes is an effective way to improve your flock and increase your lambing percentage, but it is also important to have experts such as your veterinarian on hand if things don’t go as smoothly as you hoped.
Various schools of thought exist regarding the breeding of lambs. Some breeders do not want to interfere with nature and prefer to leave a ram with the ewes so that they can come into heat and breeding can proceed naturally. Others follow the synchronisation route – here lambs are born within four to five days of each other and the breeder is better able to manage the lamb crop.
This technique is gaining in popularity with intensive and extensive livestock producers alike using it. However, the concept does require some understanding of the biology of the breeding cycle.
Read more about Evaluating the body condition of ewes in intensive systems
How hormones work
The breeding cycle is driven by the hormones progesterone and oestrogen. Progesterone dominates during pregnancy and between oestrus cycles; when it decreases, oestrogen increases. During this time, the ewes start showing heat and are ready to mate.
In order to synchronise a flock of ewes to come into heat at the same time, progesterone must be increased artificially using intravaginal sponges (CIDRs) that release progesterone. Upon removal of the CIDR progesterone decreases and the ewes come into heat. Once this happens, the ewes are injected with a hormone stimulant, pregnant mare serum (PMSG), to boost conception.
An accurate dose of PMSG must be administered to prevent ewes that are not yet ready to produce multiples, from conceiving and carrying multiples and not making it in the long run.
A management tool
Hendriette Stafford of Ramsem says that synchronising ewes is actually a very affordable method of improving the management of the sheep flock.
“A growing number of breeders are making use of the method because it is so straightforward and affordable. They are also achieving excellent results. Assisted by the synchronising agents, all ewes reach oestrus simultaneously, facilitating planning and shortening the lambing period. It is also effective in increasing the ewes’ fecundity (number of lambs).
She says it has been proven that synchronised ewes tend to produce more twins and triplets. Retaining ram lambs and the ewes that carry multiples will raise a flock’s fertility, which in turn will boost the breeder’s income. Every breeder’s ideal is to have as many multiples as possible, but this places an additional burden on pregnant ewes carrying multiple foetuses and those caring for multiple lambs.
Breeders will not increase their lamb crop through synchronisation alone, says Stafford. Your planning must be on point and management actions such as vaccination, dosing, feeding, shearing, weaning, and selection are all factors that can improve the lambing percentage.
Advantages of synchronisation
- Not only is the process very successful in practice – it is also cost-effective.
- Application is straightforward and the breeder can do it him- or herself.
- Ewes are in heat at the same time and all ewes that conceive upon synchronisation usually lamb within four to five days of each other. This promotes the planning that goes into lambing periods and the optimal use of lambing pens. The period ewes spend in kraals or lambing pens, or on the field, is shorter and therefore reduces labour and feed costs.
- Lambs are the same age. This simplifies weaning, and a large group of lambs will be market ready simultaneously.
- Predator control is also easier because the breeder can keep a watchful eye on the lambs.
- It promotes management and record-keeping, as well as the management of nutrition – feed is provided for a shorter period because ewes are all at the same stage of pregnancy.
- Another management priority is selection. With synchronisation, breeders can make better use of top-quality rams and speed up genetic progress. Observing rams will also reveal those with libido and mating dexterity issues.
- Pregnancy tests are easier since the gestation period is the same.
- Vaccination programmes run smoothly, especially when live vaccines are used.
Read more about the ins and outs of on-farm lambing pens.
Note though that there is also a downside to synchronisation. The weather can be unpredictable and severe cold, snow, rain, and wind can lead to losses. However, breeders are familiar with the environments they farm in and can plan ahead to minimise losses.
“Breeders who synchronise must also employ reliable people who are able to accurately scan ewes to verify whether they are carrying multiples. This way, ewes pregnant with multiple foetuses can receive extra attention to eliminate potential issues such as ketosis,” says Stafford.
Synchronising ewes is an effective way to improve your flock and increase your lambing percentage, but it is also important to have experts such as your veterinarian on hand if things don’t go as smoothly as you hoped. – Koos du Pisanie, Stockfarm
For more information, phone Hendriette Stafford on 082 900 3903/4 or 051 412 6327.
