Advancing breeding season and increasing production in flocks

Obtaining a good lamb price is often associated with early lambing flocks.

However, achieving a good lambing percentage to drive high ewe output is perhaps more challenging without well planned use of a hormonal intervention programme. Achieving a compact lambing period is also key to reducing labour costs and having lambs ready for market at the target time.

Brian Hanthorn, a Beef and Sheep Adviser at the College of Agriculture, Food and Rural Enterprise (CAFRE) said: “Two of the key targets for an early lambing flock are a litter size of 1.65 lambs reared per ewe and to have 90 per cent of lambs sold within 16 weeks of age.

“Sheep are seasonal breeders and begin to come into heat or oestrus as daylight hours decrease. While some specific lowland breeds will mate early in the year, most lowland breeds and cross bred ewes within the Northern Ireland flock need veterinary intervention to aid them to lamb early in the season and improve their prolificacy.

“There are a number of different programmes that can be used to help ewes come into season early and produce a good crop of lambs.

“ Two of the most common programmes are progestogen impregnated sponges with PMSG and secondly melatonin implants.”

Using progestogen impregnated sponges as part of the breeding programme allows a group of ewes to be mated as a batch on one day, and the use of a hormone injection PMSG will increase ovulation rates and in turn improve litter size.

Brian Hanthorn continued: “The main benefits of sponging and PMSG to the early lambing flock are an improvement in litter size; compact lambing – ewes that hold to first service will typically lamb within a four to five day period; repeats - ewes mated to second or subsequent oestrus will lamb from 15 days onwards and advances the breeding season around six weeks ahead of normal mating time.”

Other important points to note to improve performance include that ewes should be weaned for at least six weeks before the start of the breeding programme.

Furthermore, ewes targeted for sponging should be body score 3.5-4.0. Also, use three rams together per 20 ewes and have plenty of rams available.

Ram lambs are not always recommended and rams must be fit, active and ready for work. You should order the sponges and PMSG well in advance from your Veterinary Surgeon and store the PMSG in the fridge, according to the manufacturer’s instructions. You should also read the instructions carefully on the use of all the products used in the programme.

PMSG is administered into the muscle and the amount given is breed and month dependant. Typical rates for an early lambing flock would be 500-700 international units (i.u.) per ewe.

Brian Hanthorn also spoke about the use of Melatonin implants and said: ”This is a hormone administered at the base of the ear around 35 days prior to ram introduction to the flock. It works by releasing a small amount of melatonin into the ewe similar to what the ewe produces naturally as daylight hours decrease.

“It therefore has the ability to make the ewes come into season earlier in the year and produce a lambing percentage similar to a March lambing flock.”

Brian Hanthorn concluded: “Lamb prices this spring have been encouraging, but it is still very important for early lambing flocks to produce at least 1.65 lambs per ewe. Either sheep sponging /PMSG or Melatonin implants are very useful programmes for early lambing flocks to bring forward the lambing season, make it more compact, and achieve their targets to improve output and profit.

“You should consult your veterinary surgeon about which programme is most suitable for your farm and your sheep, and follow veterinary advice at all times.”