PSII-31 Manipulation of steam-flaked corn bulk density during grain adaptation phase of beef steers: ruminal fermentation characteristics and feeding behavior

摘要

The effects of steam-flaked corn bulk density (SFC-BD) during grain adaptation phase on ruminal fermentation characteristics and feeding behavior were evaluated. Six crossbred ruminally-cannulated Angus beef steers (BW = 404 ± 42 kg; experimental units) were used in a randomized complete block design (block = BW). Steers were assigned to adaptation strategy grain-treatment: a) SFC-BD of 335g/L (335); or b) 412g/L (412). Steers were fed ad-libitum during six 7d phases consisting of: HAY; step-up (1, 2, 3, and 4); and a common 335 SFC-BD FINISHER diet. Respective SFC-BD treatments were fed throughout step-up diets. Ruminal pH was continuously measured (wireless pH probes), and ruminal fluid collected for further analyses. A continuous observation (24h) was used for feeding behavior. Data were analyzed using GLIMMIX procedures of SAS. SFC-BD did not affect (P ≥ 0.19) measured variables, except for increasing NDF (P < 0.01) and tending to increase (P = 0.09) ADF digestibility for 412 steers during step-up 2 and 3. Steers fed 412 had greater (P ≤ 0.05) DMI during step-up 3 and 4 compared to FINISHER. Greater (P ≤ 0.01) digestible DMI during step-up 4 and FINISHER were observed compared to other phases. Digestible NDF/ADF intakes were greatest (P ≤ 0.05) during HAY-phase. Digestibility of DM was lowest (P ≤ 0.05) during HAY-phase. Steers ruminated more (P ≤ 0.05) during HAY-phase than FINISHER. Chewing was greatest (P ≤ 0.05) for HAY and intermediate for Step-up 1. Ruminal C2:C3 decreased (P < 0.01) as steers advanced through phases. Ruminal ammonia-N was greatest (P < 0.01) for step-up 1 and 2, and intermediate for other phases. The SFC-BD range studied seemed to not dramatically affect ruminal fermentation characteristics and feeding behavior. The most critical moment evidenced was between HAY and the receiving diet, as well as, when 412 g/L was suddenly switched to 335 g/L.