Alteration of fasting heat production during fescue toxicosis in Holstein steers

A. F. Koontz, D. H. Kim, A. P. Foote, L. P. Bush, J. L. Klotz, K. R. McLeod, D. L. Harmon

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


This study was designed to examine alteration of fasting heat production (FHP) during fescue toxicosis. Six ruminally cannulated Holstein steers (BW = 348 ± 13 kg) were BW-matched into pairs and used in a 2 period crossover design experiment. Each period consisted of 2 temperature segments, one each at 22 and 30°C. During each period, 1 steer per pair was ruminally dosed twice daily with 0.5 kg of ground endophyte-infected fescue seed (E+) and the other with ground endophyte-free fescue seed (E-) for 7 d. Steers on E- treatment were pair-fed to E+ steers offered alfalfa cubes at 1.5 × NEm. On d 8 of each segment, steers were moved to individual metabolism stalls fitted with indirect calorimetry head boxes. Ruminal contents were removed, weighed, and subsampled for DM determinations. The reticulorumen was washed and filled with a buffer (NaCl = 96; NaHCO3 = 24; KHCO3 = 30; K2HPO4 = 2; CaCl2 = 1.5; MgCl2 = 1.5 mmol·kg buffer-1) that was gassed with a 75% N2 and 25% CO2 mixture before rumen incubation. During buffer incubation, an E+ or E- fescue seed extract was added at 12 h intervals to maintain treatment presentation to the animal. After a 12-h wait, heart rate, O2 consumption, CO2 production, and urinary output were recorded for 16 h. There was no difference (P = 0.931) in DMI/kg0.75 between endophyte treatments by design; however, intake decreased (P = 0.004) at 30°C. Increased temperature had no effect (P > 0.10) on other measurements and there were no significant interactions (P > 0.11) of temperature and endophyte treatment. Heart rate was unaffected by fescue treatment or environmental temperature. Percent DM of ruminal contents as well as total rumen DM/kg0.75 was increased (P < 0.0001) in E+ steers. Respiratory quotient was elevated (P = 0.02) in E+ steers. Oxygen consumption decreased (P = 0.04) and CO2 production tended to be reduced (P = 0.07) during E+ treatment. Calculated FHP (kcal/kg BW0.75) was also less (P = 0.006) in steers receiving E+ treatment. These data suggest that consumption of endophyte-infected tall fescue by cattle results in a reduction in basal metabolic rate.

Original languageEnglish
Pages (from-to)3881-3888
Number of pages8
JournalJournal of Animal Science
Issue number8
StatePublished - Aug 2013


  • Bovine
  • Fasting heat production
  • Fescue

ASJC Scopus subject areas

  • Food Science
  • Animal Science and Zoology
  • Genetics


Dive into the research topics of 'Alteration of fasting heat production during fescue toxicosis in Holstein steers'. Together they form a unique fingerprint.

Cite this