Tympanic temperature in confined beef cattle exposed to excessive heat load

Abstract

Angus crossbred yearling steers (n = 168) were used to evaluate effects on performance and tympanic temperature (TT) of feeding additional potassium and sodium to steers exposed to excessive heat load (maximum daily ambient temperature exceeded 32°C for three consecutive days) during seasonal summer conditions. Steers were assigned one of four treatments: (1) control; (2) potassium supplemented (diet containing 2.10% KHCO₃); (3) sodium supplemented (diet containing 1.10% NaCl); or (4) potassium and sodium supplemented (diet containing 2.10% KHCO₃ and 1.10% NaCl). Overall, additional KHCO₃ at the 2% level or NaCl at the 1% level did not improve performance or heat stress tolerance with these diet formulations. However, the addition of KHCO₃ did enhance water intake. Independent of treatment effects, TT of cattle displaying high, moderate, or low levels of stress suggest that cattle that do not adequately cool down at night are prone to achieving greater body temperatures during a subsequent hot day. Cattle that are prone to get hot but can cool at night can keep average tympanic temperatures at or near those of cattle that tend to consistently maintain lower peak and mean body temperatures. In addition, during cooler and moderately hot periods, cattle change TT in a stair-step or incremental pattern, while under hot conditions, average TT of group-fed cattle moves in conjunction with ambient conditions, indicating that thermoregulatory mechanisms are at or near maximum physiological capacity.

The effect of type of shade on physiology, behaviour and performance of grazing steers

“…The reduced TT of steers without access to shade (38.41ºC) compared with those with access to 80% shade (38.70ºC) between 2200 and 0400 h is in agreement with numerous studies (Gaughan et al, 2004(Gaughan et al, , 2010Brown-Brandl et al, 2005;Mader et al, 2009). Gaughan et al (2010) suggested that the reason for this may be a result of the cattle without shade trying to overcorrect TT at night in an attempt to reach homeothermy.…”

“…Under these climatic conditions heat flow may reverse direction, with stored heat being dissipated from the animal back to the environment and the body temperature may fall (Kadzere et al, 2002). Mader et al (2009) reported that cattle that had the greatest maximum TT during the day also had the least TT at night. In the present study, unshaded cattle showed the greatest daily TT amplitude (1.92ºC) followed by steers in the 35% and 80% groups (1.66ºC and 1.43ºC, respectively).…”

Behaviour, tympanic temperature and performance of dairy cows during summer season in southern Chile

“…When body temperature increases causes an increased up to one degree Celsius in rectal and tympanic temperature, increased respiratory rate (panting), causing severe reductions in voluntary feed intake (Lough et al 1990), a decline on growth rates and also milk production (Elvinger et al 1992), as well as impaired reproductive function and secretion of thyroid hormones (Al-Haidary et al 2001). Mader et al (2010) concluded that cattle with moderate levels of heat stress were able to cool down at night keeping a moderate TT the next day. In this study AT dropped sharply from values above 30 °C to near to 10 ºC.…”

Biological responses of feedlot cattle to heat load

“…However for intensively housed livestock Nienaber et al (2007) and Mader et al (2010a) defined a heat wave event as a number of successive days, typically 3 to 5, where maximum ambient conditions are above a specific threshold, i.e. HLI above 86 for an un-shaded black Angus steer (Gaughan et al, 2008b).…”

“…Mader et al (2010a) indicated that as TA approaches body temperature, sweating becomes a key physiological mechanism for heat dissipation. In cattle, each individual hair follicle is associated with an apocrine sweat gland; therefore hair follicle density has a direct association to the number of sweat glands an animal has and its ability to dissipate excess body heat via evaporation (Collier et al, 2008).…”