title: Effects of canola seed supplementation on intake, digestion, duodenal protein supply, and microbial efficiency in steers fed forage-based diets.
abstract: Fourteen Holstein steers (446 +/- 4.4 kg of initial BW) with ruminal, duodenal, and ileal cannulas were used in a completely randomized design to evaluate effects of whole or ground canola seed (23.3% CP and 39.6% ether extract; DM basis) on intake, digestion, duodenal protein supply, and microbial efficiency in steers fed low-quality hay. Our hypothesis was that processing would be necessary to optimize canola use in diets based on low-quality forage. The basal diet consisted of ad libitum access to switchgrass hay (5.8% CP; DM basis) offered at 0700 daily. Treatments consisted of hay only (control), hay plus whole canola (8% of dietary DM), or hay plus ground canola (8% of dietary DM). Supplemental canola was provided based on the hay intake of the previous day. Steers were adapted to diets for 14 d followed by a 7-d collection period. Total DMI, OM intake, and OM digestibility were not affected (P > or = 0.31) by treatment. Similarly, no differences (P > or = 0.62) were observed for NDF or ADF total tract digestion. Bacterial OM at the duodenum increased (P = 0.01) with canola-containing diets compared with the control diet and increased (P = 0.08) in steers consuming ground canola compared with whole canola. Apparent and true ruminal CP digestibilities were increased (P = 0.01) with canola supplementation compared with the control diet. Canola supplementation decreased ruminal pH (P = 0.03) compared with the control diet. The molar proportion of acetate in the rumen tended (P = 0.10) to decrease with canola supplementation. The molar proportion of acetate in ruminal fluid decreased (P = 0.01), and the proportion of propionate increased (P = 0.01), with ground canola compared with whole canola. In situ disappearance rate of hay DM, NDF, and ADF were not altered by treatment (P > or = 0.32). In situ disappearance rate of canola DM, NDF, and ADF increased (P = 0.01) for ground canola compared with whole canola. Similarly, ground canola had greater (P = 0.01) soluble CP fraction and CP disappearance rate compared with whole canola. No treatment effects were observed for ruminal fill, fluid dilution rate, or microbial efficiency (P > or = 0.60). The results suggest that canola processing enhanced in situ degradation but had minimal effects on ruminal or total tract digestibility in low-quality, forage-based diets.
authors.affiliation: Department of Animal and Range Sciences, North Dakota State University, Fargo, 58105, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Leupp
authors.forename: G P
authors.initials: GP
authors.lastname: Lardy
authors.forename: S A
authors.initials: SA
authors.lastname: Soto-Navarro
authors.forename: M L
authors.initials: ML
authors.lastname: Bauer
authors.forename: J S
authors.initials: JS
authors.lastname: Caton
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D029741:Brassica rapa; D002417:Cattle / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D004063:Digestion / Q000502:physiology*; D004386:Duodenum / Q000378:metabolism; D004435:Eating / Q000502:physiology; D008297:Male; D008897:Panicum / Q000378:metabolism; D012417:Rumen / Q000737:chemistry / Q000378:metabolism*