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United States Department of Agriculture

Agricultural Research Service

Research Project: Optimizing the Biology of the Animal-Plant Interface for Improved Sustainability of Forage-Based Animal Enterprises

Location: Forage-animal Production Research

Title: Effect of fescue toxicosis on ruminal kinetics, nitrogen and energy balance in Holstein steers)

item Koontz, Anne
item Foote, Andrew
item Kim, Do
item Klotz, James
item Mcleod, Kyle
item Harmon, David

Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract only
Publication Acceptance Date: 3/8/2013
Publication Date: 7/8/2013
Citation: Koontz, A.F., Foote, A.P., Kim, D.H., Klotz, J.L., Mcleod, K.R., Harmon, D.L. 2013. Effect of fescue toxicosis on ruminal kinetics, nitrogen and energy balance in Holstein steers. J. Anim. Sci. Vol. 91, E-Suppl. 2:92.

Interpretive Summary:

Technical Abstract: This study was designed to examine alteration of ruminal kinetics, as well as N and energy balance during fescue toxicosis. Six ruminally cannulated Holstein steers (BW=217 ±7 kg) were weight-matched into pairs and pair-fed throughout a cross-over design experiment with a 2x2 factorial treatment structure. Factors were endophyte (infected, E+ vs. uninfected, E-) and feeding level (1.8 x NEm, H vs. 1.1 X NEm, L). During each period after 8d of diet adaptation one steer per pair was ruminally dosed with ground endophyte-infected fescue seed (E+), the other with ground endophyte-free fescue seed for the remainder of the period. In situ degradation of ground alfalfa was determined on d13-16. Total fecal and urinary collections were performed on d17-21, with animals placed into indirect calorimetry head-boxes during d20 and 21for determination of heat production (HP) using the Brower equation. Liquid and particulate passage rates were evaluated using Cr:EDTA and iADF respectively on d 22 and 23. There was no difference (P > 0.9) in DMI/kg.75 between endophyte treatments, and DMI/kg.75 was different (P < 0.01) between H and L intake by design. Animals on H feeding had higher (P < 0.01) water, N, and energy intakes. Energy and N excretion, as well as retained N, DE, ME, RE, and HP were higher (P < 0.03) for H v L. There were no differences in retained N, DE, ME, HP, or partial efficiency of energy use (P > 0.15) between endophyte treatments. Neither rate nor extent of in situ degradation was altered by intake level or endophyte treatment (P > 0.3). Dry matter percentage and DM weight of rumen contents were increased (P < 0.01) by E+ dosing. Particulate passage was decreased by both intake (P < 0.01) and endophyte (P = 0.02). Ruminal liquid passage rate increased (P = 0.03) with H feeding and tended to be reduced (P < 0.15) with E+ dosing. Total VFA concentration increased with both H feeding (P < 0.01) and E+ dosing (P < 0.01). Despite these differences, the N and energy balance data indicate that reduced weight gain during fescue toxicosis is primarily a function of reduced intake and not secondary effects of alkaloid ingestion.

Last Modified: 8/24/2016
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