Location: Forage-animal Production ResearchTitle: Development of a fescue toxicosis model using a fescue seed extract Author
Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2010
Publication Date: 7/11/2010
Citation: Koontz, A.F., Bush, L.P., Klotz, J.L., Mcleod, K.R., Schrick, F.N., Harmon, D.L. 2010. Development of a fescue toxicosis model using a fescue seed extract. J. Anim. Sci. 88:(2/J). Dairy Sci. 93( 1)/Poult. Sci. 89(1):704. Interpretive Summary:
Technical Abstract: This study was designed to examine the efficacy of a fescue seed extract for inducing fescue toxicosis in cattle. Four growing Holstein steers (BW = 309±36kg) surgically fitted with ruminal cannulas were utilized in a four phase crossover design experiment. The basal diet consisted of endophyte free fescue hay fed ad libitum. In phases 1 and 2, steers were ruminally dosed twice daily with 1kg either ground endophyte infected seed (SE+) or ground endophyte free fescue seed (SE-) for 7 d in order to develop a baseline of physiological responses during fescue toxicosis. In phases 3 and 4, steers were ruminally dosed twice daily with an extract from endophyte infected seed (EE+) or endophyte free fescue seed (EE-) for 7 d. During d 4-7 of each phase room temperature was increased to 32°C (HS). Steers on both SE+ and EE+ had reduced serum prolactin on D7. Steers on SE+ and EE+ had a reduction in total intake (P < 0.05) during HS, while there was no difference between treatments during thermoneutrality. Rate of intake was also reduced for SE+ and EE+ during HS. Consequently, animals on SE+ and EE+ tended to lose weight (-2.0 kg) while animals on SE- and EE- tended to gain weight (+8 kg). Skin temperature was higher (P < 0.01) during HS for both SE- and SE+. Core body temperature was higher (P < 0.0001), for extract treated animals as compared to those dosed with ground seed for both E+ and E-. Heart rate measurements show the opposite effect for both form and endophyte comparisons. There was no effect of treatment on respiration rate at thermoneutrality, however, HS tended to increase respiration rate for all treatments (P < 0.1) with E+ dosed animals higher than E- (P = 0.0002), as well as S animals higher than E (P = 0.0012). Blood pressure was only measured during E treatment. Systolic pressure was unaffected by treatment (P = 0.203), while diastolic pressures were higher for EE+ (P = 0.008). HS resulted in a reduction in systolic and diastolic pressure for EE+ (P < 0.05), while EE- pressures were unchanged. These data indicate a fescue seed extract model is able to mimic the symptoms of fescue toxicosis induced by seed.