@wbvs58 and I both suggested checking his gums and I mentioned anaplas as a possibility. Gums (and vulva in a cow/heifer) should be a nice, healthy pink - not white. Eyes should be white, not jaundice. But yes, a blood test will provide a definitive answer.
Other signs of anaplasmosis are limping, staggering, drooling, losing condition, lagging. Late stage is aggression, even if they're normally docile, and death not far behind. BTW limping & staggering, because it's neurological. Took numerous videos of one of my cows that I could NOT figure out what was going on, even though I had her in the chute numerous times. Didn't even occur to me to check her gums because I was focused on her feet, possible stifle, how she was walking. Finally took her to the vet and blood test was positive. Still early stage and LA300 stopped the progression, but she would always test seropositive.