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My question may seem trivial; but do venomous reptiles need to invenomate prey ( f/t, pre-killed ect ) in order to digest; and if they do how does a venomoid possibly digest properly?

Title: The effect of rattlesnake venom on digestion of prey

Authors: Thomas, R, Pough, FH

Citation: Toxicon 17N3 (1979) 221-228

Abstract: Rattlesnake venom injected into live mice before they were swallowed by non-venomous snakes speeded the process of digestion. This effect of venom was more pronounced when digestion was tested at 15°C than at 25°C. The proteolytic activity of viperid venom appears to facilitate the entry of a snake's stomach secretions into the prey's body cavity, inhibiting bacterial activity and thereby reducing the risk of prey putrefying before it can be digested. This effect would be particularly valuable for snakes that eat very large prey in relation to their own body size or that normally experience low body temperatures after feeding. Viperid snakes comprise a disproportionately large fraction of the total snake fauna at high altitudes in North America and Africa. Proteolytic venom appears to be one of a group of characters that permit viperid snakes to swallow and digest large prey. A digestive function of venom probably appeared at an early stage in the evolution of vipers.
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So, yeah venom probably helps to aid in more rapid digestion of prey although I am willing to bet that the effect is minimized when feeding frozen/thawed mice or rats to venomous snakes. Can venomous snakes digest prey without envenomating? Of course. I have a number of rattlesnakes that rarely strike the mice that they eat simply because they have been in captivity long enough to become habituated to eating pre-killed prey. These animals digest their mice well enough to live and thrive like the snakes that do inject venom into their prey before ingestion. So I think that it is safe to say that any digestive properties of venom are not necessary to the survival of the venomous animal, although they may be beneficial.

I forgot to mention something of interest in that article that I cited. The authors mentioned that the effect of digestion by the venom was greater at lower temperatures, which seems important in showing how this digestive effect may have evolved.

Thank you for some insite to a lingering question in my head.