title: Influence of feed intake fluctuation and frequency of feeding on nutrient digestion, digesta kinetics, and ruminal fermentation profiles in limit-fed steers.
abstract: Nine crossbred beef steers (344 +/- 26 kg) fitted with ruminal cannulas were used in a randomized complete block design to evaluate the effects of feeding 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% fluctuation in a day-to-day feed intake. In Period 2, steers were reallocated across 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 were 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. Ruminal 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 digestibilities 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 frequency or intake fluctuation. A frequency x fluctuation x sampling time interaction occurred (P < .01) for ruminal pH. Steers fed a constant amount of feed once daily had higher (P < .05) ruminal pH at 0, 3, 18, and 24 h than steers fed once daily with a 10% fluctuation in feed intake. Total VFA concentration was greater (P < .01) at 9 h after the 0800 feeding when feed was offered once vs twice daily. Feeding twice daily increased (P < .05) the molar proportion of acetate and decreased (P < .05) the molar proportion of propionate. Increasing feeding frequency resulted in a more stable ruminal environment; however, the increased acetate:propionate ratio with twice-daily feeding might result in lower efficiency of energy utilization by limit-fed steers.
authors.affiliation: New Mexico State University, Las Cruces, 88003, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Soto-Navarro
authors.forename: C R
authors.initials: CR
authors.lastname: Krehbiel
authors.forename: G C
authors.initials: GC
authors.lastname: Duff
authors.forename: M L
authors.initials: ML
authors.lastname: Galyean
authors.forename: M S
authors.initials: MS
authors.lastname: Brown
authors.forename: R L
authors.initials: RL
authors.lastname: Steiner
mesh_terms: D000821:Animal Feed; D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism; D004040:Dietary Carbohydrates; D004063:Digestion; D002149:Energy Intake; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009584:Nitrogen; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism*
chemical_list: D004040:Dietary Carbohydrates; D009584:Nitrogen