-
Views
-
Cite
Cite
J. R. Baber, J. E. Sawyer, L. A. Trubenbach, T. A. Wickersham, 031 Effect of time of concentrate delivery on nutrient digestibility, ruminal fermentation, and solid passage rate in limit-fed steers consuming wheat straw, Journal of Animal Science, Volume 94, Issue suppl_1, February 2016, Page 15, https://doi.org/10.2527/ssasas2015-031
Close - Share Icon Share
Abstract
Delivery of limit-fed, total-mixed rations requires significant capital investment and creates logistical challenges. Separate delivery of forage and concentrate portions of the diet may decrease feeding cost. Therefore, effects of time of concentrate delivery in limit-fed steers consuming wheat straw were compared using 4 ruminally cannulated steers (371 ± 12 kg BW) in a 4×4 Latin square. Intake was restricted to 80% of NRC predicted NEm requirements such that steers ate 52.88 g/kg EBW0.75 of a diet consisting of wheat straw (35%), cracked corn (29%), and distillers' grains (27%) formulated to contain 1.58 Mcal NEm/kg. Treatments were: concentrate fed 2 h prior to wheat straw (-2S), concentrate and wheat straw in a TMR (TMR), concentrate fed 2 h after wheat straw (2S), and concentrate fed 12 h after wheat straw (12S). Periods were 20 d each: 11 d adaptation to treatment, 7 d intake and digestion, 1 d ruminal fermentation profile, and 1 d passage rate determination. Nutrient intakes were similar, as designed (P ≥ 0.73), and DE intake averaged 10.4 Mcal/d. Treatment had no significant effects on DM or OM digestion (P ≥ 0.88). Dry matter digestion ranged from 69.2% for 12S to 68.3% for TMR. There was no effect on NDF digestion (P = 0.90) which was 61, 63, 63, and 62% for -2S, TMR, 2S and 12S, respectively. Gross energy digestion did not differ (P ≥ 0.90) among treatments, with 12S having greatest GE digestibility (70.3%). No differences were observed for rate of particulate passage (P ≥ 0.55), or ruminal DM fill (P ≥ 0.19), which averaged 3.8 kg. Differences in VFA concentration were not detected (P = 0.65). A time × treatment interaction was observed for pH, acetate and propionate proportions (P ≤ 0.05), but not for acetate to propionate ratios (P = 0.23). Nadir of pH was consistently observed 4 to 8 h after concentrate was delivered, but mean ruminal pH was similar among treatments (P = 0.22) ranging from 6.44 to 6.55 for 2S and 12S, respectively. Interactions resulted from a phase shift caused by anchoring analysis relative forage delivery; if evaluated relative to concentrate delivery, no time × treatment effect would be observed. Acetate proportion decreased directly after concentrate was delivered, whereas propionate increased. These findings suggest delivering forage and concentrate separately will not change digestion, and timing of concentrate delivery has little impact on ruminal fermentation.
