Sheep Scanning and Fetal Number: Welfare and Management Implications
Pregnancy Scanning in Ewes: Welfare Benefits and Applications
Ultrasound pregnancy scanning of ewes — identifying pregnancy status and fetal number — is one of the most cost-effective welfare and production management tools available to sheep farmers. By targeting nutritional and management resources according to individual ewe requirements, scanning dramatically reduces the incidence of twin lamb disease, starvation, mis-mothering, and lamb mortality.
The Welfare Case for Scanning
The fundamental welfare benefit of scanning is enabling targeted nutrition in late pregnancy. Ewes carrying triplets or quads have dramatically higher energy requirements than singles or barren ewes. Without scanning, feeding all ewes the same ration means: single-bearing ewes become over-fat (increasing dystocia risk), while triplet-carrying ewes are underfed (increasing twin lamb disease, weak triplets, and rejection). Scanning resolves this welfare problem by enabling individual-level nutrition management.
Optimal Scanning Timing
The ideal scanning window is 6-8 weeks before lambing, when fetal number can be accurately determined and nutrition adjusted in time to influence outcome. Scanning too early (before 6 weeks) has lower accuracy for multiples; too late allows insufficient time for nutritional adjustment to have effect. External factors — weather, facilities, scanner availability — affect practical timing.
Sorting and Group Management
Following scanning, ewes are sorted into management groups:
- Barren ewes: Minimal supplementary feeding required; early culling of poor-conditioned barren ewes improves flock efficiency
- Single-bearing ewes: Moderate supplementary feeding, typically 0.2-0.4 kg concentrates/day from 6 weeks before lambing
- Twin-bearing ewes: Higher feeding level: 0.4-0.6 kg concentrates/day from 6 weeks
- Triplet/quad-bearing ewes: Highest energy input: 0.6-0.8 kg concentrates/day, often with additional high-quality hay or haylage; consideration of early housing; potentially triplet reduction (careful ethical considerations apply)
Impacts on Lamb Welfare
Studies consistently show that farms implementing scanning and targeted feeding achieve: reduced lamb mortality (particularly from starvation/exposure), better colostrum production in adequately-fed ewes, reduced incidence of mis-mothering (less stressed, adequately-fed ewes mother better), and higher lamb birth weights. These translate directly to improved lamb welfare outcomes across the lambing period.
Economic and Welfare Return
The economic return on pregnancy scanning — reduced lamb losses, better condition in ewes, targeted feed use — consistently exceeds the cost of scanning within the same season. The combined economic and welfare case makes pregnancy scanning a near-universal recommendation for commercial sheep flocks lambing over 100 ewes.
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