Rancherfred, could it be something as simple as a Vitamin A deficiency?

Symptoms of vitamin A deficiency

 

One of the first easily detected signs of vitamin A deficiency in cattle is night blindness. An easy way to check for this condition is to place an obstacle in the pathway of cattle and notice if they stumble over it at twilight. Other early signs are loss of appetite, rough hair coat, dull eyes, slowed gains and reduced feed efficiency. Diarrhea and pneumonia may be the first indicators, especially in young animals. Later developments include excessive watering of the eyes, staggering gait, lameness or stiffness in knee and hock joints, and swelling of the legs and brisket (and sometimes in the abdominal region). Feedlot cattle with advanced vitamin A deficiency often pant excessively at high temperatures and go into convulsions when excited.

 

Signs of vitamin A deficiency in breeding herds include lowered fertility and calving percentage. Cows abort, drop dead or weak calves, and are difficult to settle.