Ah, OK. My cousin is a trucker and just posted something on Facebook about this. It's not just pet food. A bunch of truckers have been stranded along I-80 (which is closed because of severe winter weather) for days now, and this has caused a lot of supply problems. So that's probably the issue. Some areas have opened up so maybe the situation will improve soon.
200+ Miles of I-80 in Wyoming to Remain Closed Well Into Tuesday
200+ Miles of I-80 in Wyoming to Remain Closed Well Into Tuesday