Diet and forage quality of intermediate wheatgrass managed under continuous and short-duration grazing

Abstract

Diet quality and forage quality were determined under short-duration and continuous grazing of intermediate wheatgrass (Agropyron intermedium) in 72-day grazing trials in 1985 and 1986. The short-duration unit was divided into 8 subunits grazed sequentially for 3 days each. Six crossbred heifers and 2 esophageally fistulated steers were randomly assigned to each grazing treatment. Animals were weighed and fecal samples, pasture samples, and diet (esophageal masticate) samples were collected in each of the three 24-day periods. In vitro organic matter disappearance (IVOMD) of steer diets under short-duration grazing declined linearly across periods of both years and across days within periods in 1986. Crude protein content of steer diets under short-duration grazing declined quadratically across periods in 1986. Crude protein and IVOMD content of steer diets under continuous grazing declined linearly in 1985. The effects of 4 maturities of intermediate wheatgrass on digestibility and ruminal kinetics were compared in a 4 × 4 Latin square design with 4 ruminally and abomasally fistulated crossbred wethers. Organic matter intake and digestibility, in situ rate and extent of NDF digestion, liquid passage rate and particulate mass flowing from the rumen decreased linearly with increased forage maturity. These data suggested that effects of forage maturity or period of grazing had similar effects on diet quality and forage quality. However, diet quality under short-duration grazing also declined across days within subunits.