Consumption of endophyte-infected @entity18959 during summer months can result in severe @entity221 in @entity291 . Six heifers (296+/-8.3 kg BW) were used to determine changes in body temperature control that occur with consumption of an endophyte-infected @entity18959 diet during controlled heat challenge. All animals were exposed in five separate periods to a step increase in ambient temperature (Ta) from 21 to 31 degrees C while fed E+ (5 microg ergovaline x kg(-1) x d(-1)) or endophyte-free (E-) diets. Core body temperature (Tcore) was monitored continuously using implanted, telemetric temperature transmitters. Heat production and @entity393 were also measured at selected times to identify primary effects of E+ on thermal balance. Pretreatment Tcore exhibited a diurnal rhythm at a constant Ta of 21 degrees C, with high and low values at 2300 and 1300, respectively. An increase in daily averaged Tcore (P < 0.001) occurred with an increase in Ta from 21 to 31 degrees C. Likewise, all phases of the daily cycle increased equally during this challenge. This increase at 31 degrees C was associated with higher levels of respiration rate, skin temperature, respiratory vaporization, and skin vaporization (P < 0.05) and lower blood levels of @entity1955 (P < 0.05). Intake of the E+ diet further elevated Tcore in heifers during the short-term heat challenge (2 d), and the effect was most pronounced at 0000 to 0300 and declined thereafter. The increase in Tcore during E+ treatment was associated with an increase in respiration rate (P < 0.05), whereas metabolic heat production, skin temperature, skin vaporization and respiratory vaporization were unaffected. These results show that consumption of an E+ diet during continuous heat challenge results in a marked increase in core body temperature, especially during nighttime exposure to heat @entity1642 , due primarily to a reduction in cutaneous heat transfer, with no effect on heat production or other measured avenues of @entity393 .

Thermoregulatory ability of beef heifers following intake of endophyte-infected XXXX during controlled heat challenge.

@entity1642 :: ('MESH:D015775', 'Disease') :: ['stress'] @entity221 :: ('MESH:D005334', 'Disease') :: ['hyperthermia'] @entity1955 :: ('MESH:D013974', 'Chemical') :: ['thyroxine'] @entity18959 :: ('4606', 'Species') :: ['tall fescue'] @entity393 :: ('MESH:D034381', 'Disease') :: ['heat loss'] @entity291 :: ('9913', 'Species') :: ['cattle']
@entity18959 :: (4606,Species) :: ['tall fescue']
