That's a really nice looking dehydrator!
Ground beef carries more risk than whole strips of beef, so it has to be treated a little differently to stay safe.
Unless you are adding Cure #1 to the mix (contains 6.25% Sodium nitrite), or are using a pre-made mix which contains sodium nitrite, then Do NOT use a lower temp! 160° is right at the edge of where you should be drying uncured ground meat. I personally wouldn't go below 165°
If you add 1 level tsp Cure #1 per 5 lbs ground beef, or if you're using a pre-made mix which contains sodium nitrite, THEN you can safely dry at a lower temp for a longer period.
Cure #1 prevents Botulism, and the 165° temp will take care of any E. Coli or Salmonella.
The more dry the final product is, the less likely it will be able to harbor any dangerous bacteria or grow mold.
P.S. Some common brand names of Cure #1 are: Prague Powder #1, DQ Cure #1, Insta-Cure #1. Just make sure it contains 6.25% sodium nitrite.
Hope this helps!