My horse has had a cough for the past 2 weeks. It starts up as soon as we trot and once he has finished the coughing fit seems ok with ridden work. Hay is dampened and has been analysed and foung to be 'good' apparently. I was wondering if it is some kind of pollen allergy. Was particularly bad today. He has not got a snotty nose and seems ok in himself.He is out on restricted grazing in the day and in at night. Should I be calling the vet?