Dogs can use beta-carotene, but cats cannot convert it to Vitamin A and must receive Vitamin A itself in the diet. Signs of toxicity include anorexia, weight loss, sensitivity to touch, and loss of bone density which may cause fractures. Kittens and puppies require about 200 IU of Vitamin A per kilogram of body weight per day, adult cats and dogs about 75 IU per kilogram per day. Commercial pet foods probably contain adequate amounts of Vitamin A. Green tea, which can be found as an extract in some antioxidant combinations Selenium, which is synergistic with Vitamin E and a component of the antioxidant glutathione peroxidase, which is produced by the body. Puppies and kittens need about 5 mg of selenium per kilogram of body weight per day, adult cats 1.6 g, and adult dogs 2.2 g per kilogram per day.
Selenium can be toxic in overdose.
Signs of toxicity including vomiting, anorexia, nervousness, staggering gait, weakness and difficulty breathing. There is some controversy as to whether SOD taken orally is actually absorbed from the gut into the bloodstream. Zinc can be toxic in overdose. Too much zinc will cause imbalances in calcium and copper. Signs of toxicity include vomiting, diarrhea, anemia, loss of hair color, constipation, tetany, lameness, stiffness, or reluctance to move.