Influence of feed intake fluctuation and frequency of feeding on nutrient digestion, digesta kinetics, and ruminal fermentation profiles in limit-fedsteers

Nine crossbred beef steers (344+/-26 kg) fitted with ruminal cannulas were used in a randomized complete block design to evaluate the effects of feedi ng frequency and feed intake fluctuation on total tract digestion, digesta kinetics, and ruminal fermentation profiles in limit-fed steers. In Period 1, steers were allotted randomly to one of four dietary treatments: 1) feed offered once daily at 0800; 2) feed offered once daily at 0800 with a 10% fluctuation in day-to-day feed intake; 3) feed offered twice daily at 0800 and 1700; and 4) feed offered twice daily at 0800 and 1700 with a 10% fluct uation in a day-to-day feed intake. In Period 2, steers were reallocated ac ross treatments. The 90% concentrate diet was fed at 90% of the ad-libitum consumption by each steer. Chromium-EDTA and Yb-labeled steam-flaked corn w ere intraruminally infused at 0800 on d 1 and 3 and Co-EDTA and Er-labeled steam-flaked corn were infused on d 2 and 4 of the 4-d collection period. R uminal samples were collected at 0, 3, 6, 9, 12, 15, 18, and 24 h after the 0800 feeding, and total feces were collected for 4 d. Total tract digestib ilities of OM, N, and starch were lowest (fluctuation x frequency, P <.05) when feed was offered twice daily with a 10% fluctuation in intake. Ruminal fluid volume and passage rate were not affected (P >.10) by feeding freque ncy or intake fluctuation. A frequency x fluctuation x sampling time intera ction occurred (P <.01) for ruminal pH. Steers fed a constant amount of fee d once daily had higher (P <.05) ruminal pH at 0, 3, 18, and 24 h than stee rs fed once daily with a 10% fluctuation in feed intake. Total VFA concentr ation was greater (P <.01) at 9 h after the 0800 feeding when feed was offe red once vs twice daily. Feeding twice daily increased (P <05) the molar pr oportion of acetate and decreased (P <.05) the molar proportion of propiona te. Increasing feeding frequency resulted in a more stable ruminal environm ent; however, the increased acetate:propionate ratio with twice-daily feedi ng might result in lower efficiency of energy utilization by limit-fed stee rs.