Application of washed rumen technique for rapid determination of fasting heat production in steers

Authors: KIM, DO - University Of Kentucky; MCLEOD, KYLE - University Of Kentucky; Klotz, James; KOONTZ, ANNE - University Of Kentucky; FOOTE, ANDREW - University Of Kentucky; HARMON, DAVID - University Of Kentucky

Submitted to: Symposium on Energy and Protein Metabolism and Nutrition
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2013
Publication Date: 9/9/2013
Citation: Kim, D.H., Mcleod, K.R., Klotz, J.L., Koontz, A.F., Foote, A.P., Harmon, D.L. 2013. Application of washed rumen technique for rapid determination of fasting heat production in steers. In: Energy and Protein Metabolism and Nutrition in Sustainable Animal Production. 134:235-236.

Interpretive Summary:

Technical Abstract: Two experiments were conducted to evaluate the use of a washed rumen technique as an alternative approach for determining fasting HP in cattle. In Exp. 1, 8 Holstein steers (322±30 kg) were adapted to a cubed alfalfa-based diet (1.5xNEm) for 10 d. After which steers were placed into individual head-boxes and respiratory gas exchange was continuously measured on 2 consecutive d to determine RQ and HP under unwashed (fed state; d11) and washed rumen (fasted; d 12) conditions. On d of the washed rumen procedure, feed was withheld and reticulorumen was emptied, washed, and refilled with buffer (NaCl=96; NaHCO3=24; KHCO3=30; K2HPO4=2; CaCl2=1.5; MgCl2=1.5 mmol/kg of buffer; aerated with a mixture of 75% N2 and 25% CO2) prior to measurement of gas exchange. In Exp. 2, 6 Holstein steers (360±22 kg) were used in a replicated 3x3 Latin Square design, with 21 d periods, to determine the effects level of alimentation on RQ and HP under unwashed (d 20) and washed rumen (d 21) conditions. Treatments were a cubed alfalfa-based diet fed at 1.0, 1.5, and 2.0×NEm . Respiratory gas exchange and washed rumen procedures were conducted as described for Exp. 1. Jugular blood samples were collected at 0, 4, 8, 12, 16, 20, 24 h on d 20 and 21. In Exp. 1, HP was lower for washed rumen than for unwashed rumen (P<0.001). Over the 24 h period, RQ declined from 1.15 initially to 0.80 during unwashed conditions, whereas RQ decreased from 0.81 to 0.72 for washed rumen over the same time period (treatment x time; P<0.001). Fitting RQ data obtained during washed rumen conditions to a one-phase decay equation showed that plateau was achieved by h 8 and plateau of RQ was 0.72±0.01. During Exp. 2, HP increased (P<0.001) with energy intake for both the unwashed (479.2, 587.1, and 713.4 kJ/d·kg0.75) and washed rumen (334.4, 356.6, and 409.9 kJ/ d·kg0.75), however, the ratio of HP for washed rumen to unwashed (0.70, 0.61, and 0.57) decreased as energy intake increased from 1.0, 1.5, to 2.0×NEm. For the unwashed rumen, RQ plateau was 0.76, 0.83, and 0.87 for 1.0, 1.5, and 2.0×NEm intake, respectively. In contrast, RQ plateau for the washed rumen was 0.72, 0.71, and 0.71 for the same range of energy intake. Mean daily plasma insulin, and glucose concentrations were lower for washed rumen than unwashed rumen (P<0.001), whereas cortisol, non-esterified fatty acid (NEFA) and ß-hydroxybutyrate (BHBA) were higher for washed rumen than unwashed rumen (P<0.001), however, the NEFA and BHBA levels did not exceed thresholds for a severe energy deficit which can be induced from prolonged fasting durations. In conclusion, these studies demonstrate that a fasting state has been emulated by using the washed rumen technique in a shorter term than that of the traditional fasting methodologies without a severe energy deficit. This approach may provide an alternative to the traditional 48 h fasting time. Applying the washed rumen technique may be a more rapid and less stressful means to predict energy required for maintenance in cattle.