Performance and Forage Intake of Beef Steers Grazing Annual Ryegrass Varieties Differing in Water Soluble Carbohydrate (WSC) Content.

This study aimed to compare the animal performance of beef steers grazing annual ryegrass varieties selected to have differential water soluble carbohydrate (WSC; Lonestar, (conventional) vs Enhancer, (high WSC)) content. Steers grazing both varieties were either individually supplemented daily with cracked corn at 0.75% live weight basis or were not supplemented. Two 2 ha paddocks were planted during mid-October and grazing began in mid-March due to a dry fall and abnormally cold winter. Experimental design was a split-plot design with grass variety as main plot and corn supplementation as sub-plot. Twenty-four steers (324 ± 15.7 kg initial BW) were assigned to one of four paddocks (2 replicates per variety), with 6 animals per paddock. Within each paddock replicate three animals were supplemented (average 2.7 kg DM as cracked corn/animal/day) and three animals per paddock were not supplemented. Cracked corn supplements were provided to individual steers using Calan gates (American Calan Inc., Northwood, NH). Put and take stocking was utilized to maintain similar forage allowance among paddocks. Average daily gain was calculated by weight difference between initial and final weight, using double unshrunk weights on consecutive days. Corn intake was measured daily. Titanium dioxide was used to estimate total DM and grass intake. Animals received daily oral administration of pork-gelatin capsules containing 10g titanium dioxide during a 21d period. Fecal grab samples were collected twice daily (approximately 150 g wet material/ animal) during the last 6 days of titanium dioxide administration. Titanium dioxide concentration in feces will be assessed by concentrated H2SO4 digestion and spectrophotometry at 410 nm. Since grazing is still underway and diet and fecal samples have not yet been analyzed, final results will be analyzed and presented in the poster.