Influence of soybean hull supplementation on rumen fermentation and digestibility in steers consuming freshly clipped, endophyte-infected tall fescue.
Six steers (288.6 +/- 2.1 kg of BW) fitted with rumen and duodenal cannulas were used in a crossover design to evaluate intake, rumen fermentation, and site of nutrient digestion of freshly clipped, endophyte-infected (E+) Kentucky 31 tall fescue with or without soybean hull (SH) supplementation at 0.60% of BW (OM basis). Steers were placed in metabolism units within an environmentally controlled room and provided with free-choice access to fresh forage, water, and a vitamin/mineral supplement. The spring growth of E+ tall fescue was harvested daily during the experiment. Supplement was fed at 0700 with approximately 65% of the estimated daily forage. To maintain a fresh forage supply, additional forage was stored in a cooler and fed at 1900. Periods were 21 d with 14 d of adaptation and 7 d of digesta sample collection. Chromic oxide was used as a marker of duodenal digesta flow. Duodenal samples were taken 4 times daily with times shifting by 1 h each day to represent all 24 h of a day. Treatments were considered significant at P < 0.05. Supplementation of SH decreased forage OM intake from 1.64 to 1.41% of BW but increased total OM intake from 1.64 to 2.01% of BW. Apparent percentages (53.1%) and quantities (2,786 g/d) of rumen OM disappearance were not affected by supplementation. Percentages of total tract OM disappearance were not different (70.8%). Percentages of apparent rumen NDF disappearance also were not different (65.6%). Percentages of N disappearance were not different. Supplementation of SH resulted in increased total N (34.1 g/d) and microbial N (17.1 g/d) flowing to the duodenum. Rumen pH (6.5) was not affected, and rumen ammonia concentrations exhibited a time x treatment interaction in which SH decreased ammonia for 12 h after supplementation. Total VFA concentrations (103.9 mM) were unaffected. Liquid dilution rate (12.7%/h) and rumen OM fill (4.3 kg) were not different between treatments. Supplementation of SH at a rate of 0.60% of BW (OM basis) to calves consuming fresh E+ tall fescue decreased forage consumption but resulted in greater total intake, greater flow of N to the duodenum, and increased total tract OM disappearance.
Richards
C J
CJ
Department of Animal Sciences, The University of Tennessee, Knoxville, 37996, USA. chris.richards@okstate.edu
Pugh
R B
RB
Waller
J C
JC
D000641:Ammonia / Q000032:analysis; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002417:Cattle / Q000502:physiology*; D018592:Cross-Over Studies; D004043:Dietary Fiber / Q000008:administration & dosage / Q000378:metabolism*; D019587:Dietary Supplements; D004063:Digestion / Q000502:physiology; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D009753:Nutritive Value; D006109:Poaceae / Q000378:metabolism* / Q000382:microbiology; D011897:Random Allocation; D012417:Rumen / Q000737:chemistry / Q000378:metabolism*; D013025:Glycine max / Q000378:metabolism*; D013997:Time Factors
D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D000641:Ammonia; D009584:Nitrogen