Synchronising ewes is the management practise to achieve a compact lambing system. There are significant benefits in terms of ease of management of the flock from mating right through until slaughter of lambs – such as having the majority of the lambs at a uniform age.
The demand for consistent quality finished lambs from Mid-March onwards means a proportion of the national flock needs to lamb in December/January.
Sheep are seasonal breeders – in ewes oestrus begins as daylight hours start to decrease in the autumn. While there are some breeds that will naturally commence oestrous cycles in July/early August for the vast majority of the breed types in the Irish National Flock, oestrus can be induced by using progestagen impregnated sponges.
The use of sponges allows for oestrus to be synchronised and thereby allows the use of PMSG to be used to increase ovulation rates and ultimately the litter size of ewes successfully mated.
It is important to note that both the progestagen sponge and PMSG are prescription only medicines and manufacturers or veterinary guidelines should be followed at all times.
To make the practise of synchronising ewes cost effective, there are very specific targets to aim for – 70% of ewes should lamb down with a litter size of 1.7 per ewe lambed and 90% of lambs sold by 16 weeks of age.
The feeding system for early lamb production will mean relying heavily on concentrate feed and brassica crops as the lambing and rearing phases of the production cycle take place outside of the normal grass growing season.
Ewes in body condition score 2.5 – 3.0 generally respond well to a rising plane of nutrition for at least three weeks before and during the mating period. It is recommended to feeds ewes on a coarse ration or concentrates which are high in protein and energy, while offering high quality leafy grass.
Typically, ewes for mating should be offered 0.5 kilogram per head per day in the flushing period to have ewes increasing in body condition. This will increase ovulation rate and can enhance embryo survival in early pregnancy.
If feeding brassicas, these can be supplemented with forage or straw as brassicas are low in fibre. It is important to offer additional supplementation with brassicas as they contain varying amounts of toxin substances which could depress appetite. Mineral supplementation must be provided for ewes being offered brassicas.