I use the Dr Mercola Probiotic for him and give him 1/2 capsule with each meal
Mercola Probiotics | Complete Probiotics - Mercola.com. I give him the human grade not pet grade. He eats wet food so it's easy to add to his food. I used to give him Jarrow Petdophilus
Jarrow Formulas : Pet Dophilus. There are also other good brands. For his fish oil he gets is Iceland Pure
Vista CA Fish Oil for Pets & Animals by Iceland Pure I also give him Fying Basset colustrum a few times a week to boost his immunity.
The Flying Basset :: 100% Pure Colostrum Powder -8oz $27.95