Tendency toward higher ADFI leading to increased G:F suggests that the higher apparent feed intake may have been an artifact of higher feed wastage. Otherwise the increased intake would be expected to improve ADG.
I frequently see Capsicum positioned as a way to combat heat stress, but I'm just not convinced. Too many examples like this one where no benefit is seen, or in-fact the opposite is observed (sow trends discussed at the top are also unflattering to this compound).
If the gene expression data is truly worthwhile (no real discussion of it here), then some sort of encapsulation may be necessary. Or training piglets to eat it young, with a hit to performance at that age, to hopefully be offset later on when he pigs are older.
Liu et al (2013) also showed reduced ADFI in piglets fed Capsicum. It may be time to conclude that pigs, like my kids, just don't like spicy foods.