ARS | Publication request: Protein and Carbohydrate Interactions Alter Ruminal Fermentation, Digesta Characteristics, and Behavior in Lactating Dairy Cattle

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 7, 2009
Publication Date: September 6, 2009
Citation: Hall, M. 2009. Protein and Carbohydrate Interactions Alter Ruminal Fermentation, Digesta Characteristics, and Behavior in Lactating Dairy Cattle. In: Proceedings of Eleventh International Symposium on Ruminant Physiology, September 6-9, 2009, Clermont-Ferrand, France. p. 202-203.

Technical Abstract: The effect of altering dietary nonfiber carbohydrate complement and ruminally degradable protein was evaluated in an incomplete partially balanced Latin square design with a 2 x 2 factorial arrangement of treatments (trt) and two 21-d periods. Eight ruminally cannulated Holstein dairy cows were randomly assigned to a series of dietary trts: supplementation with the nonfiber carbohydrates (NFC) sucrose (SUC) or corn starch (STA) at 10% of diet DM, and relative modification of dietary ruminal protein degradability (RDP) by supplementation with 48% soybean meal (+RDP) or expeller soybean meal + 48% soybean meal (-RDP). All diets contained 33% corn silage and 22% alfalfa silage, on a DM basis. Diets were formulated to contain 30% NDF, 17.3% CP, and 41% NFC. Cows were offered the diets ad libitum. Sample and data collections were made in the last 7 d of each period. DM intake did not differ among treatments (P>0.56). Ruminal pH was lower with SUC than STA diets (P=0.01), and a NFCxRDP interaction showed lower ruminal pH with -RDP than +RDP for SUC, and +RDP than –RDP for STA (P<0.01). The sum of millimolar concentrations of acetate, propionate, butyrate, valerate, and lactate and the carbon they contain was greater with SUC (P<0.01). The carbon in organic acids tended to follow the inverse of the NFCxRDP pattern shown for pH: greater for SUC-RDP than +RDP, and greater for STA-RDP than +RDP (P=0.08). Ruminal NH4 was greater with SUC+RDP than –RDP, but did not differ by RDP treatment with STA (NFCxRDP effect, P=0.04). Digesta DM% tended to be lower with (14.5%) than for STA (15.0%)(P=0.06). Digesta DM kg did not differ by trt (mean = 13.1 kg; P>0.19), but digesta liquid kg was greater for SUC (79.2 kg) than for STA (72.2 kg; P<0.01). Rumination did not differ by trt (mean = 441 min/d; P>0.21), but time spent both eating and standing were greater on the –RDP trt (RDP effect: P<0.03), with the difference between +RDP and –RDP being greater with SUC than with STA (NFCxRDP effect, P<0.05). That ruminal fermentation and digesta characteristics and behaviour changed with changing dietary NFC source and relative level of RDP, suggest that such dietary changes can alter nutrients available to the animal, passage kinetics, and maintenance requirements, thus affecting animal performance.