Seasonal Change in Nutritive Value of Bluestem Pastures

Abstract

Esophageally fistulated steers were used to determine organic matter intake and digestibility of bluestem pastures during the summer grazing season. Following a 48-hour total fecal collection period, esophageally fistulated steers were used to collect grazed samples of native pastures during June, July, August, September, and October. Esophageal samples were higher in ash and crude protein and lower in crude fiber, N-free extract, and acid detergent fiber than were hand-clipped samples. In vitro dry and organic matter digestibilities were higher in forage collected by cattle than in hand-clipped forage. Multiple regression equations were developed to predict in vitro digestibility. Only crude protein and acid-detergent fiber were highly correlated with digestibility. Average daily intakes of organic matter, digestible crude protein, and digestible energy by steers on pasture were estimated from fecal nitrogen regression established from hay trials. Protein apparently became limiting about mid-July and energy in late August. The positive effects of burning were increased forage yield and weight gain with lowered lignin content.