Effects of roughage inclusion and particle size on performance and rumination behavior of finishing beef steers

Abstract Text:

This experiment was conducted to determine the effects of feeding 5 or 10% corn stalks at various grind sizes with 30 or 25% wet corn gluten feed (WCGF), respectively, on rumination behavior, animal performance, and carcass characteristics of finishing beef steers.  Fifty-one crossbred beef steers (BW = 881 ± 8 lbs), outfitted with rumination monitoring collars, were used in a randomized complete block design.  Corn stalks were either passed through a commercial tub grinder once (large grind; LG) or twice (short grind; SG).  Steam-flaked corn-based finishing treatment diets included: 10% SG with 25% WCGF (10%SG), 5% SG with 30% WCGF (5%SG), and 5% LG with 30% WCGF (5%LG).  Animals were fed once daily at 0900 h using Calan head gates for an average of 155 d (heavy block = 148 d, light block = 162 d).  Particle size of individual ingredients and treatment diets were quantified using the Penn State Particle Separator.  Data were analyzed using the MIXED procedure of SAS with animal as the experimental unit.  Means were separated using LSMEANS with the PDIFF option.  There were no differences (P = 0.52) in final shrunk body weight between 5%SG, 5%LG, and 10%SG (1401, 1393, and 1373 ± 25.46 lbs, respectively), ADG (3.8, 3.8, and 3.7 ± 0.08 lbs, respectively; P = 0.14), or G:F (0.180, 0.175, and 0.176 ± 0.003, respectively; P = 0.27).   However, DMI was greater (P = 0.03) for steers consuming the 5%LG diet compared to the 10%SG (21.9 and 21.0 ± 0.31 lbs, respectively).  Dressing percent also was greater (P = 0.05) for steers consuming 5%LG compared to 5%SG and 10%SG (64.3, 63.1, and 62.5 ± 0.007%, respectively). Hot carcass weight tended (P = 0.10) to be greatest for steers fed 5%LG.  Steers consuming 10%SG had the greatest daily minutes of rumination (P < 0.001) followed by 5%LG, and 5%SG being the least (310, 288, and 244 ± 2.98 min/d, respectively).  Steers consuming a longer particle size had increased dry matter intake and dressing percent, and tended to have greater carcass weights.  With similar roughage inclusion rate, steers consuming a longer particle size also had increased daily rumination minutes.  Therefore, increasing roughage particle size has the potential to allow a decrease in roughage inclusion without sacrificing feedlot performance and rumen function.

Keywords: rumination, corn stalks, corn gluten feed