Thanks for the article which at least activate the possible interest and problems related with that group of products. It's a pity that the number of animals and replicates is so low and the design doesn't look very strong, otherwise there would have been more significant differences. For example liverweight differences of 3.7%, 7% and 11% should normally be significant.
Also a bodyweight of only 1260 grams at 35 days looks to me very poor and not representative. In most countries birds are 1 kg heavier at that age. Treatments influences on Body weight of 22.1% and 15% and -1.1% are strange.
FCR's are on PIG level, not on poultry level.
Effects on liver and spleen like they are documented here, would reveal some toxic effects. But then strange that they are lower when used with higher intervals.
It would be good to rerun the experiment with a proper design with much more animals and replicates involved and a a modern realistic production level.