Multi-study analysis comparing salinomycin with narasin

A multi study analysis was performed to compare the efficacy of salinomycin with narasin. The analysis was performed using data of 18 different anticoccidial sensitivity tests (ASTs) conducted over a 7-year period (2013-2019). The Eimeria isolates were collected in commercial farms from 13 different countries all using different coccidiosis control programmes. Sensitivity of Eimeria parasites to anticoccidial products can be assessed by performing AST trials (Cervantes & McDougald, 2022). Faecal samples were collected in commercial farms from 13 different countries.

In all farms coccidiosis prevention was done by inclusion of anticoccidial products in the feed. The historical use and nature of the products at the time of sample collection was different for each sample. Sensitivity trials were conducted by 2 different research institutes, using comparable, standardised AST protocol. Groups of birds, reared in cages, were supplemented with salinomycin or narasin starting 2 days before oral inoculation with the different Eimeria field strains. The inclusion rate of both ionophores was always identical per trial and varied between 60 and 70 ppm. Feed samples were collected, and the target concentration of the coccidiostats were confirmed. From day of allocation until the end of the trial, average daily gain (ADG), average daily intake (ADI) and feed conversion ratio (FCR) were evaluated. All variables were analysed using a linear mixed effects model with the treatment, research institute and an interaction between them included as fixed effects, and a random effect for the specific study.

The estimated marginal means were used to evaluate the differences. On average, the salinomycin group had a higher ADG (45.1 g/day vs. 44.0 g/day, p = 0.14) and ADI compared with the narasin group (84 g vs 82.2 g, p = 0.04). The FCR was lower (better) in the salinomycin group (2.03 vs 2, p = 0.36) even without applying a correction for the higher weights. When calculating the averages per treatment the salinomycin group had a higher ADG and ADI compared with the narasin group. The FCR also improved in the salinomycin group even without applying a correction for the higher weights. When evaluating performance of different ionophores there will always be a difference between results of samples collected on different farms.

Main drivers for the efficacy are the intrinsic efficacy of the product and the historical use of the different products on the farm. The best possible way to evaluate the difference between products is to do a multi study analysis using samples with different background and evaluate their average performance. This study indicated that birds treated with salinomycin had a higher ADG and ADI compared with birds treated with narasin. The FCR was lower (better) in the salinomycin group even without applying a correction for the higher weights.