Kale is a commonly grown garden vegetable. However it can be poisonous if consumed by ruminants.
There will be a rapid loss of condition and anemia. Other symptoms include hemoglobinuria (blood in urine), temperature to 105°F, jaundice. The blood may be thin and watery.
Injections of Vitamin B-12 and iron are recommended. (I would suggest consulting with a vet before giving iron injections.)
Simply, never give kale to ruminants. They can consume limited amounts of if without any trouble; but why take the chance?
Iron injections can have disastrous results. It would be best to discuss this issue with your vet.