Data-driven analysis of lamb mortality - Final report

Key results:

  • Abortion was the primary cause of lamb mortality, accounting for over 50% (18 of 34) of the season's recorded losses.
  • Poor mothering was also noted as a key driver for lamb losses, which could be addressed by improving ewe Body Condition Score (BCS).
  • Post-turnout risks were minimal for mortality, but clinical analysis identified Parasitic Gastroenteritis (PGE) and Cobalt/Vitamin B12 deficiency.

Background:

Improving flock productivity is paramount to sustainable sheep farming, and improving output in the number of lambs reared is pivotal to that. This project investigates the 2025 lambing season mortality data from a flock of 400 ewes to benchmark performance and identify actionable areas for improvement ahead of the 2026 season.

Purpose of the work:

  1. To quantify the specific percentage of lamb losses at each stage of the production cycle for accurate farm benchmarking.
  2. To identify the single largest cause of lamb mortality in the perinatal period to implement a targeted disease prevention strategy.
  3. To design a simple, cost-effective protocol for immediate implementation to further reduce losses below the current 6.5% rate.

What we did:

The methodology involved comprehensive data collection by the farmer and subsequent veterinary analysis. All lamb losses were recorded during the 2025 lambing period, categorising them by cause (e.g. abortion, poor mothering) and production stage. This raw data was subsequently analysed to develop a plan to improve on future seasons. 

Outcomes:

Initial scanning results indicated a promising 130% scanning rate, projecting a total potential lamb crop of 520 lambs. A retrospective loss analysis was conducted, quantifying mortality rates across two critical periods: scanning to birth and birth to turnout.

The overall lamb loss rate was determined to be 6.5% (34 lambs), a figure that currently sits within the established industry standard for commercial flocks (<13%). While this result is statistically acceptable, the objective of this investigation is to move beyond industry averages. The core focus is to drill down into the data to identify specific, preventable causes of loss so that targeted management changes can be implemented for the 2026 lambing season, ultimately aiming to reduce mortality below the current benchmark.

The analysis of the 34 recorded lamb losses revealed that abortion was the main driver of mortality, accounting for 18 losses, or over 50% of the total recorded this season. Further investigation highlighted a higher-than-target barren rate, with 5% of ewes (20 total) being barren, resulting in a deficit of 30 potential lambs against the farm's goal of under 2%. Previous diagnostic findings identified Toxoplasmosis as a likely agent in the barren ewe group; this finding was used to contextualise the high rate of abortions reported during the season.

The majority of losses (29 lambs) occurred between scanning and the first 12 hours post-birth, with specific early life mortality causes including poor mothering and suffocation (8 losses total) suggesting a need for improved Ewe Body Condition Score (BCS) management. While post-turnout mortality was minimal, clinical analysis did identify Parasitic Gastroenteritis (PGE) and Cobalt/Vitamin B12 deficiency as persistent risk factors that could compromise growth rates in grazing lambs.

How to apply on your farm: 5 steps to reduce lamb loss

  1. Screen abortions: Sample any aborted lambs in the upcoming season to screen for additional abortion agents and definitively confirm or rule out other causes.
  2. Vaccinate replacements: Implement a Toxoplasmosis (Toxovax) vaccination programme for breeding replacement ewes at least four weeks before their first breeding season. Although it seems an expensive vaccine, the return on investment for the flock at Cornwal could be up to 238% over 5 years (assuming vaccination costs of £6 and additional 18 lambs saved annually).
  3. Assess ewe condition: Regularly assess ewes and separate thin ewes (<2 BCS) from the flock for additional supplementary feeding. It takes around 6-8 weeks for ewes to increase their BCS by one score, so regular monitoring is essential.
  4. Targeted worming: Perform Faecal Egg Counts (FEC) on lambs at four-week intervals to identify worm burdens before clinical signs develop and administer treatment only when necessary.
  5. B12 Supplementation: Plan for Vitamin B12 supplementation of lambs, particularly around the weaning period, to minimise growth checks during the transition to a grass-only diet.

Please contact timtechnegolcff@mentera.cymru if you would like to receive a copy of the full final report for this project.