This might have been discussed before, please let me know, but a quick search on the forum hasn't shown much. Assuming it hasn't I think the link between sentient lived experience and happiness isn't discussed enough in EA and Utilitarianism. 

The general premise is, that as we have different experiences this alters how our future experiences are judged with respect to happiness or sadness. As an example we can "train" our pain/comfort thresholds, to such an extent that for what some would consider torture, others would be fine with/experience joy. A more mundane example might be if I am taking a crowded train in Tanzania (where I live)  in third class on very hard cramped seats for 2 days across the country, this would be supremely uncomfortable and painful for me, whereas for many of the other passengers they seem completely comfortable and are unfazed by the journey. Similarly a Saudi Prince if put into the living conditions that much of the rural communities in least developed countries live in, would likely find this experience very unpleasant and choose to "skip" the experience rather than live through it.

Assuming the above is true for our conscious experience, then perhaps similar is true for other animals, which would have wide implications for animal farming in terms of how best to reduce negative experiences for the most animals.

Overall, perhaps the best way to increase utility is to concentrate on ensuring that the (negative) delta between peak experience is minimized. 

I should stress that I'm not completely sure on the above, I'm an avid reader rather than an expert in these fields, but I think these are questions that should be asked more in general (if they haven't already been).