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United States Department of Agriculture

Agricultural Research Service


Location: Forage-animal Production Research

Title: Alteration of fasting heat production during fescue toxicosis in Holstein steers

item Koontz, Anne
item Foote, Andrew
item Kim, Do
item Bush, Lowell
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: 3/6/2012
Publication Date: 7/15/2012
Citation: Koontz, A.F., Foote, A.P., Kim, D.H., Bush, L.P., Klotz, J.L., Mcleod, K.R., Harmon, D.L. 2012. Alteration of fasting heat production during fescue toxicosis in Holstein steers. J. Anim. Sci. Vol. 90, Suppl. 3:622-623.

Interpretive Summary:

Technical Abstract: This study was designed to examine alteration of fasting heat production (FHP) during fescue toxicosis. Six ruminally cannulated Holstein steers (BW = 348±26kg) were weight matched into pairs and utilized in a two period crossover design experiment. Each period consisted of two segments, one each at 22°C and 32°C. During each period, one steer in each pair was ruminally dosed twice daily with 0.5kg of ground endophyte infected seed (E+), the other with ground endophyte free fescue seed (E-) for 7 d. Animals were pair-fed through the experiment with the E+ animals offered alfalfa cubes at 1.5 x NEm. On d 8 of each segment, animals were moved to individual metabolism stalls fitted with indirect calorimetry head-boxes. Rumen contents were removed, weighed and subsampled for dry matter (DM) determinations. The reticulorumen was then washed and filled with a buffer (NaCl=96; NaHCO3=24; KHCO3=30; K2HPO4=2; CaCl2=1.5; MgCl2=1.5 mmol/kg of buffer) that was gassed with a mixture of 75% N2 and 25% CO2 before incubation in the rumen. During buffer incubation a fescue seed extract was added at 12 h intervals to maintain alkaloid presentation to the animal. After a 12h wait time heart rate (HR), core temperature (CT), O2 consumed, and CO2 produced were recorded for 16 h. There was no difference (P > 0.9) in DMI or DMI/kg.75 between endophyte treatments by design. However, intake decreased (P < 0.01) at 32°C. CT was unaffected by fescue treatment or temperature. Total weight of rumen contents tended to be increased (P < 0.15) and DM of rumen contents as well as total rumen DW/kg.75 was increased (P < 0.0001) in E+ animals. Increased temperature had no effect on measurements with the exception of HR and RQ. HR increased (P = 0.05) at 32°C, but was unaltered by fescue treatment. RQ was elevated (P = 0.02) in E+ animals and tended to increase (P = 0.1) at 32°C. Oxygen consumption decreased (P = 0.04) and CO2 production tended to be reduced (P = 0.07) in E+ animals. FHP was reduced (P = 0.04) in E+ animals. These data suggest that consumption of endophyte infected tall fescue by cattle results in a reduction in basal metabolic rate.

Last Modified: 10/17/2017
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