I've seen an arthritic goat hobbling around in agony.
With nature, you don't generally peacefully breathe out your dying breath, even if there are no predators. You live until life as it is is torturous enough that you no longer live.
There is no alternative to life, and death is compulsory and often painful. We, as humans, are lucky enough to be capable to, at times, make that process quick, and, at times, painless.
Predation is not wrong. The quality of life is what matters - and because of that, death is necessary.
Life offers joy, but can dish out misery just as deeply. If life gives you joy, it lasts as long as it can. If life gives you misery, the depth of it is limited by death.
No trust needed.