Utilizing laboratory and field studies to determine physiological responses of cattle to multiple environmental stressors

Scharf, B.

doi:10.1016/j.jtherbio.2011.10.002

Cited by 9 publications

(4 citation statements)

References 194 publications

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“…Over the 18 d in the CCR, strong correlations and linear relationships of THI, RR, and PS with RT were evident, in agreement with previous studies in beef cattle ( Beatty et al, 2006 ; Gaughan et al,. 2010 ; Scharf et al, 2011a , b ; Gaughan and Mader, 2014 ). The rate of rise in RR and PS per 1 °C rise in RT was 46 bpm and 0.63 unit, respectively.…”

Section: Discussionmentioning

confidence: 99%

Elliptical and linear relationships with rumen temperature support a homeorhetic trajectory for DMI during recovery of feedlot cattle exposed to moderate heat load

Sullivan

Wijffels

George

et al. 2022

Journal of Animal Science

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Most feedlot animals in Australia experience 2 to 3 moderate heat waves during summer. This study aimed to gain understanding of the physiological drivers in response to and during recovery from such events with a view to designing strategies to ensure rapid and safe recovery. Two hypotheses were tested during thermal challenge and recovery in controlled climate rooms (CCR): firstly, the feedlot steer on a grain-based diet mounts appropriate physiological responses during moderate heat load and in recovery so that i performance and physiology state after recovery is not different to the feed restricted thermoneutral (FRTN) steer. Secondly, commonly used indicators of increased heat load, e.g., respiration rate (RR), panting score (PS), body surface temperatures (ST) and water consumption (WC), reflect rumen temperature (RT) during thermal challenge and recovery at the level of daily means. In this study, 36 Angus steers (live weight (LW) 451.5 ± 22.6 kg) made up 3 cohorts of 12 animals that sequentially underwent the CCR phase. For this 18-d phase, the steers were allocated to either a moderate heat load treatment (thermally challenged, TC, n = 18) or a FRTN treatment (n = 18). The TC group underwent three periods, Pre-Challenge (4 d, temperature humidity index (THI) range of 68 to 71), Challenge (7 d, THI 73 to 84 with diurnal cycling) and Recovery (7 d, THI 68 to 71). The FRTN group were held at thermoneutral conditions in the CCR (THI 66.9 ± 0.3), and each animal was offered an amount of feed was based on the feed intake of its LW matched TC pair. Thus, as DMI fell in the TC group during Challenge, feed restriction was imposed on the FRTN group. The data were collected by trained observers were DMI, RT, RR, PS, body STs (forehead, shoulder, leg, rump) and WC. Challenge induced a heat stress response in the TC group with reduced DMI and LW, and elevated RT, RR, PS, body STs and WC (P < 0.001). These measures were unchanged or reduced in the FRTN group (P < 0.001). At the end of Recovery, the TC and FRTN groups had converged on most measures including LW. Daily mean RT of both groups showed strong linear relationships with THI, RR, PS, head ST and WC (P ≤ 0.0022) but opposing elliptical relationships with DMI; that is, as DMI fell with increasing RT for the TC group, DMI increased with rising RT for the FRTN group. In all, the feedlot steers in this study demonstrated sufficient homeorhetic capacity to adjust to moderate heat load and recover from it.

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Section: Discussionmentioning

confidence: 99%

Elliptical and linear relationships with rumen temperature support a homeorhetic trajectory for DMI during recovery of feedlot cattle exposed to moderate heat load

Sullivan

Wijffels

George

et al. 2022

Journal of Animal Science

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“…in earlier whole-seed diets that produced hyperthermia (5 μg EV • kg -1 BW • d -1 , Al-Haidary et al, 2001;9 μg EV • kg -1 BW • d -1 , Burke et al, 2001; 10 μg EV • kg -1 BW • d -1 , Spiers et al, 2004) and a reduction in FI (Burke et al, 2001). However, the 40 μg EV • kg -1 BW • d -1 used in the present study was also administered as whole seed in a recent study (Scharf et al, 2012). The reason for the increased amount required to generate a fescue toxicosis-type response is due to improvement in the assay and evaluation of EV content in the seed that results from increased grinding of the seed and drying procedure.…”

Section: Treatmentsmentioning

confidence: 81%

“…Other studies have provided evidence that intake of an E+ fescue diet by cattle reduces peripheral heat loss under hot conditions (Al-Haidary et al, 2001;Rhodes et al, 1991;Solomons et al, 1989). More recently, Scharf et al (2012) reported that Angus steers on an E+ fescue diet in the heat had lower appendage and trunk skin temperatures than control animals at 0600 and 2100 h, which was the coolest time of the day. The results of the present study and others suggest that the greater reduction in skin temperature of E+ animals during the down cycle for the daily T a is a sensitive indicator of fescue toxicosis that does not show signs of adaptation, as is the case for T re and FI.…”

Section: Heat Stress Responsementioning

confidence: 97%

“…It is our conclusion that the relative dose is more important than the absolute one. We selected 40 μg EV • kg -1 BW • d -1 as the "high" level in the present study because we hypothesized that grinding the seed would result in more EV absorption and possibly push the cattle to a greater level of hyperthermia during HS than noted by Scharf et al (2012). A relative dose of 50% less (i.e., 20 μg EV • kg -1 BW • d -1 ) might actually be equivalent to the 40 μg EV • kg -1 BW • d -1 in seed form.…”

Section: Treatmentsmentioning

confidence: 99%

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Use of different levels of ground endophyte-infected tall fescue seed during heat stress to separate characteristics of fescue toxicosis1

Spiers

Wax

Eichen

et al. 2012

Journal of Animal Science

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Studies of fescue toxicosis using whole seed diets show reduced feed intake and thermoregulatory ability, but much of the seed passes undigested through the animal. Cattle were fed ground tall fescue seed at different levels to potentially facilitate digestion and absorption of toxins and identify toxin sensitivity for major characteristics of the condition [i.e., hyperthermia, reduced feed intake (FI), reduced blood prolactin]. Steers (n = 18; 350 kg BW) were housed in the Brody Climatology Laboratory at thermoneutrality (TN; 19°C) and randomly assigned to daily diet treatments with either ground endophyte-infected [E+; low and high doses at 20 and 40 μg ergovaline/(kg BW/d), respectively] or endophyte-free [E-; control at 0 μg ergovaline/(kg BW/d)] tall fescue seed. After 12 d at TN, animals received 2 d of transition to heat stress (HS; 36°C daytime, 25°C nighttime) and maintained for 14 more days. Cattle were fed twice daily at 0800 and 1600 h, with water ad libitum. Feed intake was measured at 0700 h, with skin and rectal temperatures, and respiration rate at 0600, 1100, 1600, and 2100 h. Blood was sampled on selected days for prolactin and leptin determinations. Steers fed ground E+ diet decreased (P ≤ 0.0001) FI below controls at TN, with no dose effect. Maximum FI reduction with E+ treatment was 25% at TN, with an additional 46% decrease during HS (P ≤ 0.05). By the end of HS, E+ FI increased (P > 0.05) to that of E-, suggesting recovery. Prolactin was reduced (P ≤ 0.05) in high E+ cattle below controls at study end. Leptin blood concentrations were unaffected by E+ treatment (P > 0.05) but was reduced (P ≤ 0.05) by the end of HS. Pattern of rectal temperature response to HS showed a more rapid initial increase and decline for both E+ groups compared with controls (P ≤ 0.05). Skin temperature was the only variable that identified E+ dose differences. Although there were no treatment differences at TN, skin temperature was lower (P ≤ 0.05) for high E+ steers compared with controls during HS when air temperature was reduced each day. In general, FI was more responsive to E+ toxins than body temperature or blood prolactin, declining even at TN and exhibiting dynamic activity during HS. Although body temperature response to E+ toxins appears to stabilize during HS, this is misleading as rapid change in air temperature exposes effects on skin temperature.

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Regional differences in the fescue toxicosis response of Bos taurus cattle

et al. 2014

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Cattle of the same breed from different regions of the USA may have altered responses to heat stress and fescue toxicosis. Angus steers from Missouri (MO ANG, n = 10, 513.6 ± 13.6 kg BW) and Oklahoma (OK ANG, n = 10, 552.8 ± 12.0 kg BW) were fed a diet containing either endophyte-infected (E+, 30 μg ergovaline/kg BW/day) or endophyte-uninfected (E-, 0 μg ergovaline/kg BW/day) tall fescue seed for 23 days. Diet treatment began on day 2. Animals were maintained at thermoneutrality (TN, 19-22 °C, days 1-8) and then exposed to heat stress (HS, cycling 26-36 °C, days 9-22). On day 23, ambient temperature was returned to TN and used as a recovery day. Feed intake (FI) was measured daily, with rectal and skin temperatures determined six times daily. Feed intake reduction from pretreatment levels was greater (P < 0.01) for E + (13.9 ± 0.9 versus 11.9 ± 0.3 kg/day) compared to E - (12.6 ± 0.9 versus 12.4 ± 0.3 kg/day) steers over the entire TN period, regardless of Angus group. During HS, E + cattle had reduced FI (P < 0.02; 6.9 ± 0.2 versus 8.4 ± 0.2 kg/day) compared to E - animals, independent of region of origin. A greater decrease in FI (P < 0.01) was observed for OK (12.1 ± 0.3 versus 6.2 ± 0.2 kg/day) compared to MO ANG (12.2 ± 0.3 versus 7.9 ± 0.2 kg/day) when ambient temperature was increased from TN to HS. On day 13 and days 15-22, OK ANG (E+) had reduced FI (P < 0.01, -2.21 kg) compared to OK ANG (E-), while there was no effect on MO ANG. From day 12 to day 22 of HS, daily minimum temperatures for ear, rump, and tail skin were less for E + (P < 0.05) when compared with E-treated steers, signifying peripheral vasoconstriction in E + animals. This was supported by reduced shoulder and lower tail temperatures (P < 0.01) for E + compared to E-treated OK ANG on the recovery day. In summary, regional differences in the response to fescue toxicosis exist, with peripheral vasomotor effects becoming most evident when animals are subjected to rapid changes in their environment.

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Utilizing laboratory and field studies to determine physiological responses of cattle to multiple environmental stressors

Cited by 9 publications

References 194 publications

Elliptical and linear relationships with rumen temperature support a homeorhetic trajectory for DMI during recovery of feedlot cattle exposed to moderate heat load

Elliptical and linear relationships with rumen temperature support a homeorhetic trajectory for DMI during recovery of feedlot cattle exposed to moderate heat load

Use of different levels of ground endophyte-infected tall fescue seed during heat stress to separate characteristics of fescue toxicosis1

Regional differences in the fescue toxicosis response of Bos taurus cattle

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