Performance, chewing activity, and ruminal parameters in yearling beef steers fed early-harvested sorghum silage: Effect of chop length and wheat straw addition

Two experiments were conducted to evaluate effects of silage chop length (SCL) and long wheat straw (WS) addition on performance, ruminal parameters, and chewing activity of yearling beef steers. The aim of the first experiment was to measure dry matter (DM) intake, average daily gain (ADG) and feed conversion (FC). For this, 59 Angus yearling steers were assigned to one of the four treatments in a 2 × 2 factorial arrangement. The factors were SCL (i.e., 5.8 and 9.4 mm mean particle length, MPL) and WS addition (i.e., 0 and 100 g/kg). Diets consisted of 792 g/kg of early-harvested sorghum silage (SS, Sorghum bicolor (L.) Moench.), 200 g/kg of pelleted sunflower meal, and 8 g/kg of urea and mineral–vitamin supplements. The amount of SS was reduced by 100 g/kg when WS was added to the diet. The second experiment, which aimed to evaluate ruminal parameters and chewing activity, consisted of two treatments with four rumen-cannulated steers fed with a diet comprised of finely chopped SS (5.8 mm MPL) either with or without WS. In the first experiment, SCL had no effect on DM intake, ADG or FC, while addition of WS depressed DM intake and ADG and had a negative effect on FC, without interactions between the factors. In the second experiment, WS addition reduced DM intake and volatile fatty acid concentration, but did not affect rumen pH or chewing activity. Results suggest that WS addition to these SS-based diets containing a high aNDF did not improve the ruminal environment, did not affect chewing activity and had a negative effect on steer performance, while SCL may not affect performance of beef steers.