EFFECT OF SUPPLEMENTAL RATION ON CHANGES IN BLOOD COMPONENTS OF STEERS GIVEN ACCESS TO LUSH PASTURE

Abstract

Prepasture feeding of low quality hay versus hay and grain had no subsequent effect on rumen fluid ammonia, blood urea, or plasma calcium, glucose and lactic acid concentration in steers turned out on lush pasture. Steers previously fed hay and grain had lower plasma magnesium levels on the first day on unsupplemented pasture than those fed hay prior to pasture. Supplemental feed on pasture partly alleviated the depression in plasma magnesium on the first day on pasture. Feeding supplemental hay with pasture tended to lower rumen fluid ammonia, blood urea and plasma lactic acid compared with feeding no supplement during the initial days on pasture, indicating the desirability of hay feeding during this time. A hay and grain supplement with pasture had a similar effect to the hay supplement on rumen-fluid ammonia, and plasma lactic acid, but a lesser effect on blood urea concentration. Neither supplemental hay nor hay plus grain affected plasma calcium or glucose levels. All steers showed an increase in rumen fluid ammonia, blood urea and plasma lactic acid on the first day and a decrease in plasma calcium and magnesium on the second day on pasture. Blood urea, plasma magnesium and plasma calcium concentrations had not returned to prepasture levels by 21 days on pasture.