Location: Forage-animal Production ResearchTitle: Alteration of fasting heat production during fescue toxicosis in Holstein steers Author
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.