For breeders and commercial sheep farmers, lambing season is the single most important period in the breeding year. It ultimately sets the direction for the farm, dictates management workload, and sets the foundation for next year’s flock performance.
One figure lies at the heart of both farm records and Sheep Ireland’s genetic evaluations: Number of Lambs Born (NLB).
The NLB index simply measures how many lambs each ewe produces at lambing, including lambs born alive, dead, or aborted. But behind this simple measure is a powerful tool that helps identify productive ewes, highlight fertility issues, and drive stronger maternal genetics across Irish flocks.
Why NLB matters for Commercial Farms?
NLB is a major component of the Replacement Index. For commercial farmers, this has direct, practical implications:
- More lambs reared per ewe means more output from the same flock size.
- Better maternal genetics lead to improved fertility, easier lambings, and stronger lamb survival.
- Accurate NLB records boosts the evaluations accuracy and helps to identify the ewes worth keeping—and the ones worth culling.
High‑accuracy NLB records mean better breeding decisions, and better breeding decisions mean more profit.
How NLB Is validated and why it matters?
Sheep Ireland validates NLB using several data checks to make sure the information feeding into €urostars is correct and useful. These checks also ensure breeders best-performing animals get the credit they deserve and allows commercial farmers to use these animals to improve the prolificacy of their ewes.
- Matching scanning results to lambing data
Lambing outcomes are compared to pregnancy scan results. This helps identify missing lambs, incorrect records, or unrealistically high litter sizes.
- Recording all lambs, alive or dead
To validate true prolificacy, breeders must record:
- Lambs born dead.
- Lambs that die within 48 hours
- Lamb mortality up to 100 days
This reflects the reality that lamb survival is heavily influenced by ewe genetics. Dead-at-birth and early deaths must be recorded with sex and birth weight.
- Cross‑Checking with lambing traits
NLB is validated against:
- Lambing difficulty
- Lamb vigour
- Birth weights
These traits strongly influence lamb survival and are essential for understanding whether a ewe consistently produces viable lambs.
- Linkage requirements
To maintain genetic linkage, a flock must have at least five live, weighed lambs from a linkage sire. NLB records form the first step in establishing this linkage and ensuring accurate across‑flock evaluations.
What is the impact for commercial farmers?
For commercial systems, productivity is simple: lambs sold = income.
Data across Sheep Ireland programmes consistently show that:
- High-NLB ewes (with good survival) generate more saleable lambs.
- Progeny from high Replacement Index ewes achieve better weaning weights and lower barren rates.
- Using high-star rams and ewes increases lamb survival and shortens finishing times.
CPT (Central Progeny Testing)
Validation figures shows the difference between using a 5 star ram for each index (Replacement or Terminal);
What CPT farmers and Sheep Ireland have seen from the CPT ewes, is that consistently using 5 star Replacement index rams produced:
- 21 more lambs born
- 4% less lamb mortality
- 4% better mothering ability
In the same way, consistently using 5 star Terminal index rams produced:
- 6% less lambing difficulty
- 1 heavier lambs at weaning
- 17 days quicker to slaughter
Using the LambPlus App wherever possible
It reduces errors and syncs data directly with Sheep Ireland. Avoiding paper-based delays ensures flocks accurate records.
