A decision-making framework for evaluating interventions used at weaning to reduce mortality in lightweight pigs and improve weight gains in the nursery

A decision model to aid in selecting treatments for weaned pigs was developed and tested, with the purpose of reducing nursery mortality and improving weight gain. Interventions evaluated were to not treat pigs, to treat the whole population, or to treat only a subgroup of pigs below a certain weaning weight (target treatment). Outcome was characterized as death or survival. Losses were set at zero for survivors weighing > 14.5 kg at the end of the nursery phase. Survivors weighing ≤ 14.5 were defined as lightweight pigs (LWP). Losses due to LWP and death were modeled as 30% and 60%, respectively, of the feeder pig market price ( 1974 to 2002 average, United States Department of Agriculture). Treatment effect, mortality, proportion of LWP, and treatment cost were subjected to sensitivity analysis. Losses were minimal for mortality < 7% and LWP < 18% when target treatment was used with different weaning weight cutoffs. Treating the whole population was economically efficient (mortality and LWP were at least 40% lower) if performance was poor. Each course of action evaluated may minimize losses. However, target treatment minimizes losses for a wide range of mortality, proportion of LWP, and treatment-cost situations.