Uros have shockingly strong jaws. If your uro is an adult with healthy teeth, he can likely crunch the dry lentils like popcorn. Some people do grind or soak/sprout lentils. I don't bother. Keep in mind, don't feed large amounts of dry foods unless he's also eating plenty of greens and veggies (not for you specifically, just a general caveat).
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Torey
Eugene, Oregon, USA
1.1 Saharan Uros (Joe and Arthur)
3.0 Mali Uros (Spike, Turtle, and Tank)
1.1 Ornate Uros (Scuttlebutt and Shazzbot)
1.1 Collared Lizard (Ripcord and Rorschach)
2.0 Green Anoles (Bowser and Sprocket)
1.1 Chubby Housecats (Roscolux and Jenny)