In this article, Brian Hanthorn from the College of Agriculture Food and Rural Enterprise (CAFRE) discusses advancing the breeding season and increasing production in early lambing flocks.
It is essential to achieve a respectable rearing percentage of 1.65 lambs per ewe and obtain 90% of lambs sold within 16 weeks if the system is to be profitable in a normal year.
Obtaining a good lambing percentage and, subsequently, high ewe output are more challenging without using some hormonal intervention.
A long, drawn-out lambing period is one of the main reasons why many flock owners revert to March lambing.
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 crosses within the Northern Ireland flock need some intervention to help them mate early in the season and improve prolificacy.
Synchronising ewes using sheep sponges and PMSG is probably the most common method of advancing the breeding season.
Using progestagen impregnated sponges, you can mate a group of ewes in one day as a batch. The use of a hormone injection PMSG will increase ovulation rates and, in turn, improve litter size.
A typical programme for synchronising ewes:
Table 1. Synchronisation programme for early lambing ewes.
|Insert sponges||Day 0 AM|
|Remove sponges and inject PMSG||Day 12 AM|
|Mating hogget ewes (36 hours after sponge removal)||Day 13 PM|
|Mating mature ewes (48 hours after sponge removal)||Day 14 AM|
|Remove rams||Day 16|
|Introduce rams for repeats||Day 28|
|Remove rams||Day 34|
|Scan ewes and return non-pregnant ewes to ram||Day 80|
To achieve good results with synchronising ewes, ewes should be weaned for at least 6 weeks and be in a body score 3.5-4.0 at sponging.
Using 3 experienced, fit rams together per 20 ewes is essential. Having insufficient ram power leads to very disappointing pregnancy rates.
Order the sponges and PMSG in good time as they are Prescription Only Medicines (POM) only available through your local veterinary practice.
Discuss in-depth the PMSG rate (typically 500-700 international units) with your Veterinary Surgeon. It is very important to follow veterinary advice and manufacturers administration instructions with all animal medicines.
An alternative to sponging and PMSG is a melatonin implant.
This is a hormone administered at the base of the ear around 35 days before 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.
Therefore, it can make the ewes come into season earlier in the year and produce a lambing percentage similar to a March lambing flock.
Melatonin implants have the advantage over sheep sponges in that there is a lot less handling involved.
Also, evidence suggests lambing spread is more consistent with a later lambing flock. Melatonin implants again are POM products only available through your veterinary practice.
Table 2. Melatonin implant programme
|Remove rams/ teasers from neighbouring fields and paddocks||Day 1|
|Implant the ewes at the base of the ear. Keep isolated from male sheep, this includes sight, sound and smell.||Day 7|
|Introduce rams (35 days after implantation). Peak mating activity will occur 25-35 days after the introduction of rams.||Day 42|
High lamb prices this spring have been very encouraging. However, it is still very important for early lambing flocks to produce at least 1.65 lambs per ewe and get 90 % of their lambs away within 16 weeks.
If early lambing flocks are managed at a mediocre level, then they are likely to be less profitable than March lambing flocks.
The use of either sheep sponging /PMSG or Melatonin implants are very useful methods for early lambing flocks to tighten lambing, improve output and achieve targets.
Lamb prices peaked this year around the middle of April with an unprecedented price of around £7.00 per kilo carcase and remained above £6.00 per kilo until early June.
These high prices make early lambing systems appear very financially attractive.
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