Prevention of the dry season peak in child wasting in Chad: Evidence from a cluster randomised controlled trial of integrated livestock interventions

Background: Child acute malnutrition remains persistently above emergency thresholds in Chad's Sahelian drylands, with a predictable, but rarely recognized, dry season peak linked to declining pasture and livestock productivity, reduced milk availability and heightened exposure to zoonotic infections. Humanitarian responses remain largely reactive and treatment-focused, with limited evidence on preventive strategies that address drivers embedded in local livelihood systems. We evaluated the effectiveness and return on investment (ROI) of an integrated livestock management intervention designed to prevent the dry-season peak of child acute malnutrition in pastoral and agro-pastoral communities in Chad. Methods: We conducted a cluster-randomised controlled trial in Kanem and Barh-El-Gazel provinces, Chad. Seventy-six villages were randomised (1:1) to intervention or control. Eligible households had at least one child aged 6-59 months and access to milking livestock during the dry season. The intervention (December 2024-June 2025) combined livestock feed supplementation to sustain milk production near households during the dry season, household-level zoonotic risk mitigation, and nutrition counselling. Primary outcomes were the prevalence of global acute malnutrition (GAM) and severe acute malnutrition (SAM) at the dry-season peak (May 2025), assessed in a prespecified random subsample of 52 clusters. All 76 clusters were assessed post-peak (July 2025). Analyses followed an intention-to-treat approach using mixed-effects models. A societal ROI analysis was conducted over six months with projections to 24 months. Findings: At the dry-season peak, 821 children 6-59 months from 521 households were assessed across 52 villages. GAM prevalence was 22.2% in intervention villages versus 47.4% in controls (adjusted OR 0.29 [95% CI 0.18-0.49]; p<0.001), and SAM prevalence was 4.4% versus 19.4% (adjusted OR 0.17 [0.08-0.37]; p<0.001). Intervention households had higher daily milk availability (+588 mL per household; p<0.001), and children consumed more milk (+102 mL per day; p=0.008). Odds of self-reported diarrhoeal disease and acute respiratory infection were substantially lower among children in intervention villages (aOR 0.21 [0.10-0.44] and 0.22 [0.11-0.46], respectively). Post-peak, women's dietary diversity increased (aOR 3.68 [1.90-7.13]), alongside reduced workload, lower household food insecurity and distress livestock sales, improved livestock condition, and a benefit-cost ratio of 5.40 at six months, rising to 16.40 at 24 months. Interpretation: Protecting livestock productivity and sustaining children's access to milk while reducing zoonotic exposure during the pastoral lean season effectively prevents seasonal peaks of child acute malnutrition. This integrated anticipatory action and One Health livelihood-based approach offers a scalable, dignifying, high-return lifesaving preventive model for pastoral and agro-pastoral humanitarian settings.