Effect of shade on body temperature and performance of feedlot steers

The behavior and welfare of neglected species: some examples from fish and mammals

Animal welfare is the state of an animal's body and mind and the level to which its requirements are satisfied. Animal welfare is affected by human decisions and actions. Numerous decisions concerning animals are driven by human desires to enhance their own lives, and some of these decisions may be influenced by self-interest or a strong emphasis on economic factors. How to assess the welfare state of animals is a central issue in animal welfare science. Two critical questions can be used to address animal welfare: first, is the animal healthy, and second, does the animal have what it needs? Both of these questions can potentially be answered using the study of animal behavior. The development of behavioral methodologies is crucial for evaluating welfare in contexts where concern for animal welfare is often highest, such as on intensive modern farms and sites where working animals are used. Herein, we discuss animal welfare by focusing on some of its major concepts and explanations. Later, to illustrate key aspects of animal welfare, we chose to examine the information that is available for some 'neglected' livestock species, which are commercially important on a global basis and found in large numbers: buffaloes (Bubalus bubalis), camels (Camelus dromedarius), donkeys (Equus asinus), mules (Equus asinus × Equus caballus), and lumpfish (Cyclopterus lumpus). We chose these species because there are major ongoing concerns about their welfare, and more research is required to help solve the various problems. Overall, there are strong imbalances in terms of the species that are usually studied in terms of animal welfare research, and we call for greater attention to those that have traditionally been neglected.

Effect of continuous or intermittent feeding of ergot contaminated grain in a mash or pelleted form on the performance and health of feedlot beef steers

This study evaluated the effect of feeding ergot contaminated grain continuously or intermittently through backgrounding (BG) and finishing (FN) in a mash or pelleted supplement on the growth performance, health and welfare parameters, and carcass characteristics of feedlot beef steers. Sixty black Angus steers (300 ± 29.4 kg BW) were used in a complete randomized 238-d study. Steers were stratified by weight and randomly assigned to four different diets (15 steers/treatment) and individually housed. Treatments included: (1) control [CON; no added ergot alkaloids (EA)], (2) continuous ergot mash (CEM; fed continuously at 2 mg total EA/kg of DM), (3) intermittent ergot mash (IEM; fed at 2 mg total EA/kg of DM, during the first week of each 21-d period and CON for the remaining 2 wk, this feeding pattern was repeated in each period), and (4) intermittent ergot pellet (IEP; fed at 2 mg of total EA/kg of DM as a pellet during the first week of each 21-d period and CON for the remaining 2 wk as described for IEM). Steers were fed barley based BG diets containing 40% concentrate:60% silage (DM basis) for 84 d (four 21-d periods), transitioned over 28 d (no ergot fed) to an FN diet (90% concentrate:10% silage DM basis) and fed for 126 d (six 21-d periods) before slaughter. In the BG phase, steer DMI (P < 0.01, 7.45 vs. 8.05 kg/d) and ADG (P < 0.01) were reduced for all EA diets compared to CON. The CEM fed steers had lower ADG (P < 0.01, 0.735 vs. 0.980 kg) and shrunk final BW (P < 0.01, 350 vs. 366 kg) than CON. CEM had lower gain:feed (P < 0.07, 0.130 vs. 0.142) than CON. In the FN phase, steer DMI (P < 0.01, 9.95 vs. 11.05 kg/d) and ADG (P = 0.04) were also decreased for all EA fed steers compared to CON. Total shrunk BW gain (P = 0.03, 202.5 vs. 225.2 kg), final BW (P = 0.03, 617.9 vs. 662.2 kg), and carcass weight (P = 0.06) decreased for all EA fed steers compared to CON. The percentage of AAA carcasses decreased for all EA fed steers (P < 0.01, 46.7 vs. 93.3%) compared to CON. EA fed steers had increased rectal temperatures (P < 0.01, 39.8 vs. 39.4 °C) compared to CON. Pelleting ergot contaminated grain did not reduce the impact of ergot alkaloids on any of the measured parameters during BG or FN. Continuously or intermittently feeding ergot contaminated diets (2 mg total EA/kg of DM) significantly reduced intake, growth performance, and carcass weight, with minimal impact on blood parameters in feedlot steers. Pelleting was not an effective method of reducing ergot toxicity.

Strategies to alleviate heat stress on performance and physiological parameters in feedlot-finished cattle under heat stress conditions. A systematic review-meta-analysis

Strategies to alleviate heat stress on live performance - dry matter intake (DMI), average daily gain (ADG), and feed conversion efficiency (FCE) - and on physiological parameters - respiratory rate (RR) and panting score (PS) - of feedlot-finished cattle were evaluated by systematic review-meta-analysis. Using the PICO framework were identified 3813 records, with 31 publications and 6729 cattle being considered in the meta-analysis (MA). The comparison most reported was sun vs. shade (n = 24 publications), followed by shade vs. shade (area per animal and effectivity in reduce solar load) (n = 7 publications) and sun vs. sprinkling (n = 4 publications). Cattle with access to shade with total reduction in solar load improved ADG (p = 0.008) and FCE (p = 0.024), and reduced RR (p < 0.001) compared to unshaded animals. Cattle with access to shade with a height between 3 and 4 m increased ADG (p < 0.001), tended to improve FCE (p = 0.054), and reduced RR (p < 0.001) compared to unshaded animals. An area of shade from 2 to 4 m2/animal increased ADG (p = 0.002), and higher than 4 m2/animal reduced RR (p < 0.001) compared to unshaded animals. Animals that received sprinkling volume below 1 L/animal/min improved ADG (p = 0.008) compared to unshaded animals. Cattle with access to shade with a high area per animal improved DMI (p = 0.023) and ADG (p < 0.001) compared to animals with a low area. In univariate meta-regression, it was observed that the variables significantly (P < 0.05) influencing DMI were THI category; influencing ADG were cattle gender, THI category, and coat color; influencing FCE were cattle age and hemisphere; and influencing RR were country, THI category and climate. Performance and physiological parameters of feedlot-finished cattle under heat stress depend on animal and environmental characteristics.

Heat Stress Mitigation Strategies in Feedyards: Use, Perceptions, and Experiences of Industry Stakeholders

The purpose of this study was to: (1) understand heat mitigation strategies currently used and recommended by feedyard operators, veterinarians, and nutritionists, (2) understand their perceptions of heat mitigation strategies related to cattle health, performance, welfare, and carcass quality, (3) quantify the frequency of extreme heat events, and (4) understand industry needs associated with heat stress mitigation strategies. An online survey was shared via 11 industry association listservs. Descriptive statistics were performed on 56 responses (n = 22 operators, 26 veterinarians and eight nutritionists). Thematic analysis was performed on free-response questions. Sixteen (72.7%) operators, 23 (88.5%) veterinarians and eight (100%) nutritionists utilized at least one heat mitigation strategy. "Changing processing and shipping hours" (n = 42, 75%) had the most "strongly agree" responses when asked about strategy effectiveness. The majority of respondents agreed that heat stress negatively impacts cattle health, performance, and welfare (Mean ± SD; ≥7.8 ± 2.6 for all roles). Forty-two (75%) respondents experienced cattle death loss from extreme heat events. Thematic analysis indicated that respondents perceived pen infrastructure and water/feed management as important considerations for better mitigating heat stress impacts. When asked what resources would be helpful, respondents indicated research and data regarding the effectiveness of various strategies.

The effect of day-only versus day-plus-night cooling of dairy cows

The aim of this study was to assess effects on milk yield (MY), rumen temperature, and panting score when lactating dairy cows were cooled during the day only or during the day and night. The study was conducted over 106 d during using 120 multiparous Holstein-Friesian cows assigned to 2 treatments (60 cows/treatment; 2 pens/treatment): (1) day cooling (DC): overhead sprinklers (large droplet) and fans while in the dairy holding yard only, shade and fans at the feedpad, and a shaded loafing area; and (2) enhanced day+night cooling (EDN): overhead sprinklers (large droplet) and fans in dairy holding yard, ducted air blowing onto cows during milking, plus thorough wetting (shower array) on exit from dairy; shade and fans at feedpad (turned off at night); and shaded loafing area + ducted fan-forced air blowing onto cows at night. The ducted air at night was manually activated at 2030 h when the maximum daily temperature-humidity index exceeded 75 and remained on until 0430 h the next day. The cows were fed a total mixed ration ad libitum, and feed intake was determined on a pen basis. Rumen temperature and cow activity were obtained from each cow at 10-min intervals via rumen boluses. Panting scores were obtained by direct observation 4 times a day at approximately 0430, 0930, 1530, and 2030 h. Cows were milked twice daily: 0500 to 0600 h and 1600 to 1700 h. Individual MY were obtained at each milking and combined to give individual daily totals. The EDN cows had greater daily MY (+2.05 kg/cow per day) over the duration of the study compared with DC cows. Rumen temperature during the third heat wave was lower for EDN (39.51 ± 0.01°C) than for DC (39.66 ± 0.01°C) cows. During the most severe heat wave (heat wave 3), MY for the 2 groups was similar, but over the 6 d following the heat wave, EDN cows had greater daily MY (+3.61 kg/cow per day). Rumen temperature was lower for EDN (39.58 ± 0.01°C) than for DC (40.10 ± 0.01°C) cows.

Economically sustainable shade design for feedlot cattle

Provision of shade reduces radiant heat load on feedlot cattle, thus reducing demand of water and energy for thermoregulation. While the positive effects of shade on animal welfare are widely known, the literature lacks data on the magnitude of its economic impacts. In this study, we propose the concept of novel shade design to prove that a correctly oriented and dimensioned roof structure, which optimizes shade to be displaced within the pens, motivates cattle to seek shade, protect them from short-wave solar radiation, and is resilient to counteract weather adverse conditions. The beneficial outcome is improvement in animal welfare and productive performance, as well as increments on financial return and sustainability. To attest these benefits, eight hundred B. indicus × Bos taurus bulls were randomly assigned in pens with or without shade from a galvanized steel-roof structure. Performance data (e.g., dry matter intake, body weight gain, feed efficiency and hot carcass weight) and heat stress indicators (e.g., subcutaneous temperature, body-surface temperature, respiratory rate and water intake) were assessed along the study period. The economic outcomes derived from shade implementation were determined using the net present value. Meteorological variables were also monitored every 1 min, and grouped in a thermal comfort index for feedlot cattle, the InComfort Index (InCI). The shade structure efficiently reduced radiant heat load on cattle in pens with shade. According to the classification of the InCI, during very hot days (InCI > 0.6; around noon with mean solar radiation above 800 W m^-2 and mean air temperature above 33°C), greater proportion (80%) of animals in shaded pens were using shade. Under such circumstances, cattle in shade had water intake reduced by 3.4 L per animal, body temperature was lower by 5°C, subcutaneous temperature was lower by 1°C and respiration rate was lower by 10 breaths min^-1 compared to animals in pens without shade (P = 0.0001). Although dry matter intake was similar (P = 0.6805), cattle in pens with shade had higher average daily gain reflected in a heavier hot carcass weight (8 kg animal^-1; P = 0.0002). Considering an initial investment of $90 per animal to build a structure that lasts 15 years, the expected payback time is four finishing cycles (~110 days per cycle). In conclusion, this study confirms that the proposed novel shade design is economically profitable, improves performance, and enhances animal welfare.

Removing maternal heat stress abatement during gestation modulated postnatal physiology and improved performance of Bos indicus-influenced beef offspring

This study evaluated the growth and immune response of beef calves born from Bos indicus-influenced beef heifers provided pre- and postpartum heat abatement on pasture. On 83 ± 4 d prepartum (day 0), 64 Brangus crossbred beef heifers (~¼ B. indicus) were stratified by body weight (BW; 454 ± 37 kg) and body condition score (BCS; 6.3 ± 0.28; scale 1 to 9), and then allocated into 1 of 16 bahiagrass pastures (1 ha and 4 heifers per pasture). Treatments were randomly assigned to pastures (8 pastures per treatment) and consisted of heifers provided (SH) or not (NSH) access to artificial shade (4.5 m2 of shade area per heifer) from 83 d prepartum to 50 d postpartum (days 0 to 133). Heifers and calves were managed similarly from day 133 until the start of the breeding season (day 203). Calves were weaned on day 203 (at 119 ± 19 d of age), limit-fed the same drylot diet at 3.5% of BW (DM basis) days 209 to 268 (3 to 4 calves per pen; 8 pens per treatment) and vaccinated against respiratory disease pathogens on days 222 and 236. Heifer intravaginal temperatures from days 35 to 42 were lower (P ≤ 0.03) for NSH vs. SH heifers from 0000 to 0800 hours but greater (P ≤ 0.05) for NSH vs. SH heifers from 1100 to 1800 hours. Heifer intravaginal temperature from days 126 to 132 did not differ (P = 0.99) between NSH and SH heifers. Heifers assigned to NSH had greater respiration rates from days 20 to 96 (P ≤ 0.0007), greater plasma concentration of cortisol on days 35 (P = 0.07) and 55 (P = 0.02), less plasma concentration of insulin-like growth factor 1 (IGF-1) on days 35 (P = 0.10), 55, and 133 (P ≤ 0.05), and less BCS from days 55 to 203 (P ≤ 0.01) compared to SH heifers. Calves born from NSH heifers had less birth BW (P = 0.05), greater overall plasma haptoglobin concentrations (P = 0.05), greater seroconversion against bovine respiratory syncytial virus on day 222 (P = 0.02), tended to have greater ADG from days 209 to 268 (P = 0.07), and had greater BW on day 268 (P = 0.05) compared to SH offspring. Plasma concentrations of cortisol and serum titers against other respiratory disease pathogens did not differ (P ≥ 0.15) between NSH and SH offspring. Hence, removing maternal access to artificial shade: (1) increased prepartum intravaginal temperature and plasma concentrations of cortisol but reduced prepartum BCS and plasma concentrations of IGF-1 in grazing B. indicus-influenced beef heifers; and (2) increased post-weaning BW gain and had positive effects on humoral immune response of their offspring.

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

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 climate-controlled rooms (CCR): firstly, the feedlot steer on a grain-based diet mounts appropriate physiological responses during moderate heat load and in recovery so that its 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 3 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.

Increasing shade area in feedlot heifers during heat stress: physiological and performance parameters

Heat stress is a great challenge for feedlot operations established in arid zones. The aim of this study was to evaluate if increasing shade area in the pen improved physiological and productive variables in feedlot heifers under hot climate. A total of 510 European and Zebu heifers were randomly assigned to six pens which were divided in two treatments: (1) three pens with 100 heifers each with a shade area of 2.7 m²/head (control group [C]); and (2) three pens with 70 heifers each with a shade area of 3.7 m²/head (treated group [T]). Physiological variables respiratory frequency (RF) and body surface temperature (BST) of several anatomic regions were taken from 30 heifers per treatment (i.e., 10 heifers/pen). Feed intake on pen basis was recorded weekly and heifers were individually weighted on days 1, 26, and 66 of the study to calculate performance variables. Relative humidity (RH) and ambient temperature (AT) were recorded and used to estimate the temperature-humidity index (THI). Data was analyzed with analysis of variance. The average THI during the study was 81.7 units, which was categorized as dangerous heat stress. In both shaded areas, European heifers showed higher (P < 0.05) RF than Zebu heifers. In the afternoon, the temperature of head, neck, loin, paddle, and belly was higher (P < 0.05) in C compared with T. Heifers under T showed better (P < 0.05) daily weight gain (DWG), total weight gain (TWG), feed conversion (FC), and feed efficiency (FE) than heifers in C, with no effect on dry matter intake (DMI). Results indicate that during hot summer months, Zebu showed more tolerance to heat stress than European heifers; however, heifers under a shade area of 3.7 m²/head had better productive performance than those under a shade area of 2.7 m²/head during the finishing phase of the feedlot. Increasing the shade area in the finishing phase of beef cattle on feedlot improved some physiological and productive responses during heat stress.

The influence of shade availability on the effectiveness of the Dairy Heat Load Index (DHLI) to predict lactating cow behavior, physiology, and production traits

Numerous climatic indices have been utilized to predict the effect of hot, and cold, climatic conditions on animal production and welfare. To date, the dairy industry has relied extensively on the Temperature Humidity Index (THI) to predict adverse climatic conditions; however, neither solar radiation nor air movement is accounted for in the THI equation. The Dairy Heat Load Index (DHLI) was initially developed as an alternative climate index. In its current format, the DHLI does not account for the effects of heat load mitigation strategies, such as shade, which decreases the negative effects of hot climatic conditions on lactating cows. Therefore, this experiment aimed to determine the effectiveness of the DHLI as a predictor of heat load responses in both shaded and unshaded cows, as compared with the THI. Forty lactating Holstein Friesian (n = 40) cows were selected and paired based on live weight, milk yield, and days in milk. One cow from each pair was randomly allocated to one of two treatments: shaded (n = 20) or unshaded (n = 20). Cows were given 7 days to acclimate prior to the commencement of data collection. After 28 days, cows were transitioned into the alternate treatment in a crossover design and given 7 days to acclimate prior to data collection. Behavioral observations (0800, 1200, 1400, and 1800 h daily), daily milk yield (kg), milk composition (various days), and vaginal temperature (T_VAG, °C; 5 pairs/week, over a 4-week rotation) were recorded. Overall, data from this experiment indicated that the DHLI was a better predictor of standing and feeding behaviors in unshaded cows and drinking behaviors in shaded cows. Conversely, the THI was a better predictor of standing behavior and shade usage in shaded cows. Furthermore, the THI was a better predictor of mean panting score (MPS) in shaded cows, whereas the DHLI performed better in unshaded cows. Additionally the DHLI was a better predictor of T_VAG in these cows. Finally, when evaluating the 7-day average of each climatic index, the DHLI was a better predictor of change in milk yield. Incorporation of additional animal and management factors is required if the DHLI is to become an effective heat load management tool.

The impact of weather on the incidence of dark cutting in Australian feedlot cattle

This study conducted a retrospective analysis of historical Meat Standard Australia (MSA) carcass data in combination with Bureau of Meteorology (BOM) weather data, to evaluate the relationship between climatic conditions prior to feedlot departure on the incidence of dark cutting grain-fed beef. Data records for 2,795,754 carcasses from 17 commercial feedlots over a 6-year period were evaluated within this study. Carcasses were consigned to 16 abattoirs. Weather data from BOM were recorded at 30-min intervals and were obtained from weather stations with the closest proximity to each feedlot. These data were used to calculate the Temperature Humidity Index (THI). Climatic data were amalgamated into daily observations and a series of predictors including ambient temperature (T_A, °C), relative humidity (RH, %), wind speed (WS, m/s), rainfall (mm) and THI. In addition, lag interactions from 24 h out to 28 days prior to exiting the feedlot were generated. The incidence of dark cutting was determined as percentage per cohort with an ultimate pH > 5.7. Data were analysed using three models: model 1 included feedlot, abattoir, hormone growth promotant status and sex as fixed effects. Model 2 incorporated the fixed effects within model 1 and minimum, maximum and standard deviation (SD) of T_A and RH, daily range in T_A, average WS and rainfall as random effects. Model 3 incorporated minimum, maximum, range and SD of THI, average WS and rainfall as random effects in addition to the fixed effects of model 1. The incidence of dark cutting within feedlot had a 10.1% range in estimated means with the lowest incidence was observed at feedlot 17 (0%) and highest incidence at feedlot 10 (10.1%). The inclusion of the climatic variables in model 2 and model 3 accounted for an additional 0.1 to 0.2% of the incidence of dark cutting carcasses. Higher maximum T_A, RH and THI in the 3 to 28 days prior to consignment were all associated with an increased incidence of dark cutting (P < 0.05), but not in the 48 h preceding consignment (P > 0.05). Low minimum T_A and low THI were also associated with an increase the incidence of dark cutting across all lag periods (P < 0.05). Increased variation in THI and T_A in the 48 h prior to consignment increased dark cutting (P < 0.05) while increased standard deviation (SD) of temperature and THI range also increased dark cutting in the 14 and 28 day prior to feedlot exit (P < 0.05). Smaller minimum ranges in T_A in the 28 days prior to consignment also reduced dark cutting (P < 0.05). Climatic conditions accounted for a further 0.1 to 0.2% of the incidence of dark cutting, whereas animal management factors, feedlot and abattoir were able to account for 21% of dark cutting. These data suggest that climatic conditions appear to have an inherent role in the incidence of dark cutting, albeit a small impact. Regardless, understanding the influence of climatic conditions on dark cutting allows for the implementation of management strategies within the supply chain to further reduce the impact of climatic conditions on grain-fed cattle.

Characterizing heat mitigation strategies utilized by beef processors in the United States

During lairage at slaughter plants, cattle can be exposed to extreme heat conditions from pen densities and holding pen microclimates. While research outlining heat mitigation strategies used in other sectors of the beef supply chain is available, there is no published data on the use of heat mitigation strategies at slaughter plants. The objective of this study was to characterize short-term heat mitigation strategies used by commercial beef slaughter plants in the United States. Twenty-one beef slaughter plants, representing an estimated 60% of beef slaughter in the United States, were included in the study. All plants indicated use of at least one heat mitigation strategy, and five of them used more than one type. Sprinklers/misters were the most commonly used heat mitigation type (n = 17, 81%), and fans were the least common type (n = 4, 19%). Shade usage was present in several plants (n = 7, 33%), ranging from barn style roofs to shade cloths. Respondents indicated that they believed heat mitigation strategies provide benefits both to cattle well-being and meat quality outcomes. Future research should focus on the effectiveness of these techniques in improving animal well-being and quality outcomes in the slaughter plant environment and protocols for optimum implementation.

Pathophysiology of Fever and Application of Infrared Thermography (IRT) in the Detection of Sick Domestic Animals: Recent Advances

Body-temperature elevations are multifactorial in origin and classified as hyperthermia as a rise in temperature due to alterations in the thermoregulation mechanism; the body loses the ability to control or regulate body temperature. In contrast, fever is a controlled state, since the body adjusts its stable temperature range to increase body temperature without losing the thermoregulation capacity. Fever refers to an acute phase response that confers a survival benefit on the body, raising core body temperature during infection or systemic inflammation processes to reduce the survival and proliferation of infectious pathogens by altering temperature, restriction of essential nutrients, and the activation of an immune reaction. However, once the infection resolves, the febrile response must be tightly regulated to avoid excessive tissue damage. During fever, neurological, endocrine, immunological, and metabolic changes occur that cause an increase in the stable temperature range, which allows the core body temperature to be considerably increased to stop the invasion of the offending agent and restrict the damage to the organism. There are different metabolic mechanisms of thermoregulation in the febrile response at the central and peripheral levels and cellular events. In response to cold or heat, the brain triggers thermoregulatory responses to coping with changes in body temperature, including autonomic effectors, such as thermogenesis, vasodilation, sweating, and behavioral mechanisms, that trigger flexible, goal-oriented actions, such as seeking heat or cold, nest building, and postural extension. Infrared thermography (IRT) has proven to be a reliable method for the early detection of pathologies affecting animal health and welfare that represent economic losses for farmers. However, the standardization of protocols for IRT use is still needed. Together with the complete understanding of the physiological and behavioral responses involved in the febrile process, it is possible to have timely solutions to serious problem situations. For this reason, the present review aims to analyze the new findings in pathophysiological mechanisms of the febrile process, the heat-loss mechanisms in an animal with fever, thermoregulation, the adverse effects of fever, and recent scientific findings related to different pathologies in farm animals through the use of IRT.

An updated review on cattle thermoregulation: physiological responses, biophysical mechanisms, and heat stress alleviation pathways

Heat stress is one of the main obstacles to achieving efficient cattle production systems, and it may have numerous adverse effects on cattle. As the planet undergoes climatic changes, which is predicted to raise the earth's average temperature by 1.5 °C between 2030 and 2052, its impact may trigger several stressful factors for livestock. Among these, an increase in core body temperature would trigger physiological imbalance, consequently affecting reproduction, animal health, and dry matter intake adversely. Core body temperature increase is commonly observed and poses challenges to livestock farmers. In cattle farming, thermal stress severely affects milk production and weight gain, and can compromise food security in the coming years. This review presents an updated approach to the physiological and thermoregulatory responses of cattle under various environmental conditions. Strategies for mitigating the harmful effects of heat stress on livestock are suggested as viable alternatives for the betterment of production systems.

Effects of providing artificial shade to pregnant grazing beef heifers on vaginal temperature, growth, activity, and behavior

This experiment evaluated the effects of providing artificial shade during summer on activity, behavior, and growth performance of pregnant grazing beef heifers. Thirty-six black-hided Angus and Angus crossbred pregnant heifers [418 ± 9 kg body weight (BW); approximately 90 d of gestation] were stratified by breed, blocked by BW, and allocated to 12 “Pensacola” bahiagrass pastures (Paspalum notatum Flüggé; 1.3 ha, n = 3 heifers/pasture) with or without access to artificial shade (SHADE vs. NO SHADE; 6 pastures each) for 7 wk during summer. The shade structures were composed of shade cloth (11 × 7.3 m length, 2.4 m height: 26.8 m² of shade per heifer). Shrunk BW was recorded on enrollment (day 0) and week 7 (day 47), whereas full BW was obtained on week 2 (day 14), 4 (day 28), and 6 (day 42) to assess average daily gain (ADG). Vaginal temperature was recorded for five consecutive days during weeks 1, 3, 5, and 7 using an intravaginal digital thermo-logger, and individual GPS devices were used to quantify the use of shade for an 8-h period. Activity was monitored using automated monitoring devices (HR-LDn tags SCR Engineers Ltd., Netanya, Israel) through the experimental period. Vaginal temperature was lower (P < 0.01) for heifers in the SHADE compared with heifers in the NO SHADE treatment from 1200 to 1600 h and 1100 to 1900 h for weeks 1 and 3, respectively. Heifers in the SHADE treatment spent 70% of the 8-h period evaluated under the shaded structure. Provision of shade increased (P < 0.01) daily lying time (11.4 ± 0.2 vs. 10.3 ± 0.2 h/d) and standing bouts per day (P < 0.01; 12.6 ± 0.4 vs. 10.8 ± 0.4 bouts/d), whereas it reduced (P < 0.01) standing bout duration (61.6 ± 3.0 vs. 82.9 ± 3.0 min/bout) relative to heifers without access to shade. The interaction between treatment and hour affected (P < 0.01) daily rumination time because heifers with access to SHADE had greater rumination between 1000 and 1200 h. Although ADG tended (P = 0.08) to be greater for the heifers in the SHADE treatment (0.20 vs. −0.02 kg, respectively), the access to shade did not (P = 0.79) affect the final BW. In conclusion, providing artificial shade during summer to pregnant grazing beef heifers was effective in reducing vaginal temperatures and exerted changes in heifer behaviors that translated into slight improvements in growth performance.

Impacts of shade on cattle well-being in the beef supply chain

Shade is a mechanism to reduce heat load providing cattle with an environment supportive of their welfare needs. Although heat stress has been extensively reviewed, researched, and addressed in dairy production systems, it has not been investigated in the same manner in the beef cattle supply chain. Like all animals, beef cattle are susceptible to heat stress if they are unable to dissipate heat during times of elevated ambient temperatures. There are many factors that impact heat stress susceptibility in beef cattle throughout the different supply chain sectors, many of which relate to the production system, that is, availability of shade, microclimate of environment, and nutrition management. The results from studies evaluating the effects of shade on production and welfare are difficult to compare due to variation in structural design, construction materials used, height, shape, and area of shade provided. Additionally, depending on operation location, shade may or may not be beneficial during all times of the year, which can influence the decision to make shade a permanent part of management systems. Shade has been shown to lessen the physiologic response of cattle to heat stress. Shaded cattle exhibit lower respiration rates, body temperatures, and panting scores compared with unshaded cattle in weather that increases the risk of heat stress. Results from studies investigating the provision of shade indicate that cattle seek shade in hot weather. The impact of shade on behavioral patterns is inconsistent in the current body of research, with some studies indicating that shade provision impacts behavior and other studies reporting no difference between shaded and unshaded groups. Analysis of performance and carcass characteristics across feedlot studies demonstrated that shaded cattle had increased ADG, improved feed efficiency, HCW, and dressing percentage when compared with cattle without shade. Despite the documented benefits of shade, current industry statistics, although severely limited in scope, indicate low shade implementation rates in feedlots and data in other supply chain sectors do not exist. Industry guidelines and third-party on-farm certification programs articulate the critical need for protection from extreme weather but are not consistent in providing specific recommendations and requirements. Future efforts should include: updated economic analyses of cost vs. benefit of shade implementation, exploration of producer perspectives and needs relative to shade, consideration of shade impacts in the cow–calf and slaughter plant segments of the supply chain, and integration of indicators of affective (mental) state and preference in research studies to enhance the holistic assessment of cattle welfare.

Shade availability on pasture does not affect semen characteristics of Brahman bulls (Bos taurus indicus)

Testicular degeneration by heat is the leading cause of infertility in bulls. Beef cattle are generally farmed under hot and humid conditions, and consequently, the thermotolerance of each breed must be considered in their natural environment. This study aimed to evaluate the reproductive characteristics of Brahman bulls maintained in the grazing system, with or without shadow availability. Ten Brahman bulls aging between 24 and 30 months were allocated in two different paddocks, with or without shadow availability. The heat tolerance test was performed on three non-consecutive typical summer days. The semen samples were collected at four times points in a 14 days interval. The climate conditions were monitored throughout the experiment; and clinical evaluation, testicular consistence and scrotal circumference were measured before every semen collection. In addition, semen was evaluated regarding volume, aspect, turbulence, motility, straight movement, sperm concentration, and morphological exam. The studied Brahman bulls showed a high thermolysis capacity, high heat tolerance, and no differences in semen quality were observed between groups.

Impacts of heat stress on meat quality and strategies for amelioration: a review

During the summer, high ambient temperature and humidity cause economic loss to the global livestock industry via reduced livestock productivity and increased mortality. The problem of heat stress (HS) is likely to be exacerbated by global warming and climate change. Recent research has shown that HS not only leads to physiological and metabolic perturbations in live animals but can also affect carcass and meat quality characteristics plausibly by altering the rate and extent of postmortem muscle glycolysis and resultant pH. However, these impacts of HS are not consistent across species. Higher incidence of pale soft and exudative (PSE) meat has been reported in poultry. On the contrary, higher incidence of high ultimate pH and dark firm and dry (DFD) meat or no impacts of HS have been reported in sheep and cattle. With the limited data on HS impacts on meat quality of ruminants, it is difficult to explain the exact mechanisms driving these variable impacts. However, it is hypothesized that the severity and duration of HS may lead to variable impacts due to lack of opportunity to adapdate to acute heat exposure. Longer HS exposure may allow ruminants to adapdate to heat and may not record any negative impacts on meat quality. This paper reviews the recent research on impacts of HS on meat quality characteristics and identify the key areas of further research required to better understand these negative impacts to develop strategies for amelioration. In addition, some mitigation strategies of HS have also been discussed which include both managemental and nutritional interventions.

A Scoping Review: The Impact of Housing Systems and Environmental Features on Beef Cattle Welfare

Housing systems and environmental features can influence beef cattle welfare. To date, little information has been synthesized on this topic. The aim of this scoping review was to examine the relationship between housing and welfare status, so that beef cattle producers and animal scientists can make informed decisions regarding how their housing choices could impact beef cattle welfare. Housing features were categorized by floor type, space allowance and shade availability, as well as the inclusion of enrichment devices or ventilation features. Evaluation of space allowances across feedlot environments determined behavioral and production benefits when cattle were housed between 2.5 m2 to 3.0 m2 per animal. Over 19 different flooring types were investigated and across flooring types; straw flooring was viewed most favorably from a behavioral, production and hygiene standpoint. Veal calves experience enhanced welfare (e.g., improved behavioral, physiological, and performance metrics) when group housed. There is evidence that the implementation of progressive housing modifications (e.g., shade, environmental enrichment) could promote the behavioral welfare of feedlot cattle. This review presents the advantages and disadvantages of specific housing features on the welfare of beef cattle.

Welfare of beef cattle in Australian feedlots: a review of the risks and measures

The rising global demand for animal protein is leading to intensification of livestock production systems. At the same time, societal concerns about sustainability and animal welfare in intensive systems is increasing. This review examines the risks to welfare for beef cattle within commercial feedlots in Australia. Several aspects of the feedlot environment have the potential to compromise the physical and psychological welfare of cattle if not properly monitored and managed. These include, but are not limited to, animal factors such as the influence of genetics, temperament and prior health, as well as management factors such as diet, pen design, resource provision, pregnancy management, and stock-person attitudes and skills. While current industry and producer initiatives exist to address some of these issues, continuous improvements in welfare requires accurate, reliable and repeatable measures to allow quantification of current and future welfare states. Existing measures of welfare are explored as well as proxy indicators that may signal the presence of improved or reduced welfare. Finally, potential future measures of welfare that are currently under development are discussed and recommendations for future research are made.

The influence of heat load on Merino sheep. 2. Body temperature, wool surface temperature and respiratory dynamics

Context Australia exports ~2 million sheep annually. On these voyages, sheep can be exposed to rapidly changing ambient conditions within a short time, and sheep may be exposed to periods of excessive heat load. Aims The aim of this study was to define the responses of sheep exposed to incremental heat load under simulated live export conditions. The study herein describes the influence of heat load on wool surface temperature, body temperature (rumen temperature (TRUM), °C; and rectal temperature (TREC), °C) and respiratory dynamics (respiration rate, breaths/min; and panting score (PS)) of sheep under live export conditions. In addition, the relationship between body temperature and respiratory dynamics was investigated. Methods A total of 144 Merino wethers (44.02 ± 0.32 kg) were used in a 29-day climate controlled study using two cohorts of 72 sheep (n = 2), exposed to two treatments: (1) thermoneutral (TN; ambient temperature was maintained between 18°C and 20°C), and (2) hot (HOT; ambient temperature minimum and maximum were 22.5°C and 38.5°C respectively). Sheep in the HOT treatment were exposed to heat load simulated from live export voyages from Australia to the Middle East. Respiration rate, PS and wool surface temperature (°C) data were collected four times daily, at 3-h intervals between 0800 hours and 1700 hours. Rectal temperatures were collected on five occasions at 7-day intervals. These data were evaluated using a repeated measures model, assuming a compound symmetry covariance structure. Individual TRUM were obtained via rumen boluses at 10-min intervals between Days 23 and 29 of Cohort 2. Individual TRUM data were collated and converted to an hourly mean TRUM for each sheep, these data were then used to determine the hourly mean TRUM for TN and HOT, then analysed using a first order autoregressive repeated measures model. Additionally, the relationship between respiratory dynamics and TRUM were investigated using a Pearson’s correlation coefficient, a partial correlation coefficient and a multivariate analysis of variance. Key results The respiration rate of the HOT sheep (140 ± 3.55 breaths/min) was greater (P &lt; 0.01) than that of the TN sheep (75 ± 3.55 breaths/min). Similarly, the PS of the HOT (1.5 ± 0.02) sheep was greater (P = 0.009) compared with the TN sheep (1.2 ± 0.02). Wool surface temperatures and TREC were greater (P &lt; 0.05) for the HOT sheep than for the TN sheep. There were treatment (P &lt; 0.0001), hour (P &lt; 0.0001), day (P = 0.038) and treatment × hour (P &lt; 0.0001) effects on the TRUM of TN and HOT sheep. Conclusions The climatic conditions imposed within the HOT treatment were sufficient to disrupt the thermal equilibrium of these sheep, resulting in increased respiration rate, PS, TREC and TRUM. Implications These results suggest that the sheep were unable to completely compensate for the imposed heat load via respiration, thus resulting in an increase in TREC and TRUM.

Influence of shade on panting score and behavioural responses of Bos taurus and Bos indicus feedlot cattle to heat load

Context Feedlot cattle can be negatively impacted by hot conditions, such that they have reduced performance and wellbeing. This study was conducted at the research feedlot located at The University of Queensland during a southern hemisphere summer (October to April). Aims The objective of this study was to evaluate the influence of shade on the behaviour and panting score of Bos taurus and Bos indicus feedlot cattle during summer. Methods Thirty-six steers (12 Angus, 12 Charolais and 12 Brahman) with an initial non-fasted liveweight of 318.5 ± 6.7 kg were used in a 154-day feedlot study consisting of two treatments: unshaded and shaded (3 m2/animal). Observational data were obtained for each steer at 2 h intervals between 0600 and 1800 hours daily from Day 1 to Day 154. Additional night time observational data were collected at 2-h intervals between 2000 and 0400 hours on 12 occasions. Data collected included activity (feeding, drinking, or ruminating), posture (standing or lying) and panting score. Panting scores were used to calculate a mean panting score for each breed × treatment group. Observational data were converted to a count for each breed × treatment group for each observation time point and were analysed using a binomial generalised linear model. Key results Maximum shade utilisation was the greatest at 1200 hours for Angus (85.5%), Charolais (32.7%) and Brahman (33.3%) steers. All breed × treatment groups exhibited a notable increase in mean panting score as heat load increased. Average increase in mean panting score was 0.36, where shaded Brahman exhibited the smallest increase (0.13) and unshaded Angus had the greatest increase (0.71). When heat load conditions were very hot (heat load index (HLI) ≥ 86) the mean panting score of all breed × treatment groups differed (P &lt; 0.05). Conclusions Overall these results emphasise the importance of providing shade to feedlot cattle, irrespective of genotype. Implications These results further highlight the importance of providing shade to feedlot cattle. These results challenge the general perception that Bos indicus feedlot cattle do not require access to heat load alleviation strategies.

Effects of shade location and protection from direct solar radiation on the behavior of Holstein cows

Two trials (E1 and E2) were performed to assess the behavior of eight Holstein dairy cows with 367 ± 58 kg of body weight and 10.52 ± 0.08 kg of milk yield. A 4 × 4 Latin square design (four periods of lactation and four levels of solar blockage) with four paddocks was used. Each paddock contained a wood shading structure covered with a cloth that blocked 30% (T1), 50% (T2), 70% (T3), or 100% (T4) of direct solar radiation. In the first trial (E1) each shade structure was located approximately 40 m from the feeder and water troughs; in the second trial (E2), the distance was reduced to 5 m. Air temperature (T_A, °C), relative humidity (R_H, %), wind speed (U, ms^-1), black globe temperature (T_G, K), mean radiant temperature (T_MR, K), radiant heat load (R_HL, W m^-2), and local shortwave radiation (R_S, W m^-2) were recorded at 15-min intervals from 08:00 to 17:00 h. Four behavioral activities were recorded: grazing, eating at the feed trough, ruminating, and idling. For each of these activities, animal posture (lying or upright) and location (under shade or exposed to sunlight) were recorded. The meteorological conditions showed similar variations from 8:00 to 17:00 h between the two trials. However, the air temperatures in E1 were lower (± 2 °C) than those in E2. In a PCA analysis, the first and the second principal components explained 56.87% and 21.85%, respectively, of the total variation in the behavioral variables. Under the E1 conditions, the animals did not seek shade, whereas in E2, the dairy cows spent 35 ± 5% of their time lying and idling in the shade. At a solar radiation blockage of 100%, cows were in the shade more than 60% of the time due to the intensity of solar radiation, which was 722.19 ± 14.59 W m^-2 at 11:45. In a PCA analysis, the first and the second principal components explained 65.18 and 22.3%, respectively, and 87.48% together, of the total variation in the original variables. Consequently, it was possible to develop a shade index (IST) based on the first two components. In E1, animals spent very little time in the shade, spending only 0.15% of total time under the shade, irrespective of blockage. However, E2 cows used shade, reaching almost 80% of time under the shade, at midday, when the blockage was 100%.

The influence of shade allocation or total shade plus overhead fan on growth performance, efficiency of dietary energy utilization, and carcass characteristics of feedlot cattle under tropical ambient conditions

Objective

The objective of this experiment was to evaluate the effect of shade allocation and shade plus fan on growth performance, dietary energy utilization and carcass characteristics of feedlot cattle under tropical ambient conditions

Methods

Two trials were conducted, involving a total of 1,560 young bulls (289±22 kg BW) assigned to 24 pens (65 bulls/pen and 6 pens/treatment). Pens were 585 m² with 15 m fence line feed bunks. Shade treatments (m² shade/animal) were: i) limited shade (LS) to 1.2 m² shade/animal (LS_1.2); ii) limited shade to 2.4 m² shade/animal (LS_2.4); iii) total shade (TS) which correspond to 9 m²/animal, and iv) total shade equipped with fans (TS+F). Trials lasted 158 and 183 days. In both studies, the average weekly maximum temperature exceeded 34°C.

Results

Increasing shade allocation tended (p = 0.08) to linearly increases average daily gain (ADG), and dry matter intake (DMI, quadratic effect, p = 0.03). This effect was most apparent between LS_1.2 and LS_2.4. Shade allocation, per se, did not affect gain efficiency or estimated dietary net energy (NE). Compared with TS, TS+F increased (p<0.05) ADG, gain efficiency, and tended (p = 0.06) to increase dietary NE. There was a quadratic effect of shade on longissimus area and marbling score, with values being lower (p<0.01) for LS_2.4 than for LS_1.2 or TS. Likewise, marbling score was lower for TS+F than for TS. Percentage kidney, pelvic, and heart (KPH) linearly decreased with increasing shade. In contrast, KPH was greater for TS than for TS+F.

Conclusion

Providing more than 2.4 m² shade/animal will not further enhance feedlot performance. The use of fans in combination with shade increases ADG and gain efficiency beyond that of shade, alone. These enhancements were not associated with increased DMI, but rather, to an amelioration of ambient temperature humidity index on maintenance energy requirement.

A panting score index for sheep

When exposed to hot conditions, heat dissipation via an increase in respiration rate (RR) is an important thermoregulatory mechanism for sheep. However, evaluating RR under field conditions is difficult. In cattle, a viable alternative has been to assess panting score (PS); therefore, the objective of this study was to evaluate the relationship between RR and PS to determine if a PS index can be used to evaluate heat load in sheep. One hundred and forty-four Merino wethers (44.02 ± 0.32 kg) were used within a climate-controlled study. The study was replicated twice over 29 days, where each replicate consisted of two treatments: (1) thermoneutral (TN) and (2) hot (HOT). Ambient temperature (T_A) and relative humidity (RH) were maintained between 18 and 20 °C and 60 and 70% respectively for the TN treatment. For the HOT treatment, heat load increased steadily over the 29 days. Minimum T_A was 22.5 °C and maximum was 38.5 °C, while RH decreased (60 to 30%) as T_A increased in the HOT treatment. A comprehensive PS classification was developed by enhancing the current sheep PS index and aligning the descriptors with the current PS index utilized in beef cattle studies. Respiration rate and PS were obtained for each animal at 3-h intervals between 0800 h and 1700 h daily. These data were used to determine the mean RR for each PS, across the study and within the TN and HOT treatments. The relationship between PS and RR was evaluated using a Pearson's correlation coefficient. Data were also analyzed using a general linear model to determine the impact of PS, posture and animal identification (animal ID) on RR within each PS. Unsurprisingly, RR increased as PS increased, and PS, 0 and RR, 2.5 were 30.7 ± 0.59 and 246.8 ± 12.20 bpm respectively. There was a strong relationship between RR and PS (r = 0.71; P < 0.0001). As RR increased, sheep were more likely to be observed standing (P < 0.001). Mean PS of sheep within the HOT treatment (1.49 ± 0.02) were greater (P = 0.0085) when compared to the TN (1.17 ± 0.02) sheep. Individual animal ID accounted for approximately 7-37% of the variation observed for RR across PS, indicating that animal ID and climatic conditions were influencing RR and PS. These results suggest that the comprehensive PS index described here can be used as a visual appraisal of the heat load status of sheep.

Evaluating rumen temperature as an estimate of core body temperature in Angus feedlot cattle during summer

This study was conducted to determine the relationship between rectal temperature (T_REC) and rumen temperature (T_RUM) and to assess if T_RUM could be used as a proxy measure of core body temperature (T_CORE) in feedlot cattle. Eighty Angus steers (388.8 ± 2.1 kg) were orally administered with rumen temperature boluses. Rumen temperatures were recorded at 10-min intervals over 128 days from all 80 steers. To define the suitability of T_RUM as an estimation of T_CORE, T_REC were obtained from all steers at 7-day intervals (n = 16). Eight feedlot pens were used where there were 10 steers per pen (162 m²). Shade was available in each pen (1.8 m²/animal; 90% solar block). Climatic data were recorded at 30-min intervals, including ambient temperature (T_A; °C); relative humidity (RH; %); wind speed (WS; m/s) and direction; solar radiation (SR; W/m²); and black globe temperature (BGT; °C). Rainfall (mm) was recorded daily at 0900 h. From these data, temperature humidity index (THI), heat load index (HLI) and accumulated heat load (AHL) were calculated. Individual 10-min T_RUM data were converted to an individual hourly average. Pooled mean hourly T_RUM data from the 128-day data were used to establish the diurnal rhythm of T_RUM where the mean minimum (39.19 ± 0.01 °C) and mean maximum (40.04 ± 0.01 °C) were observed at 0800 h and 2000 h respectively. A partial correlation coefficient indicated that there were moderate to strong relationships between T_RUM and T_REC using both real-time (r = 0.55; P < 0.001) and hourly mean (r = 0.51; P < 0.001) T_RUM data. The mean difference between T_REC and T_RUM was small using both real-time (0.16 ± 0.02 °C) and hourly mean T_RUM (0.13 ± 0.02 °C) data. Data from this study supports the hypothesis that T_RUM can be used as an estimate of T_CORE, suggesting that T_RUM can be used to measure and quantify heat load in feedlot cattle.

Application of microchip and infrared thermography for monitoring body temperature of beef cattle kept on pasture

The monitoring of body temperature is important for the diagnosis of the physiological state of the animal, being dependent on available methods and their applicability within production systems. This work evaluated techniques to monitor the body temperature of beef cattle kept on pasture and their ability to predict internal temperature. Twenty-three adult bovine females were monitored for six months, and collection data carried out in eleven campaigns (D0-D10) twelve days apart. During collections, the surface temperatures of ear base (ET, ^oC) and ocular globe (OGT, ^oC) were measured by infrared thermography, and the subcutaneous temperature (ST, ^oC) was measured with the use of transponder containing an implantable microchip. Rectal temperature (RT, ^oC) was considered as a reference for body temperature. Temperature and Humidity Index (THI), Black Globe Temperature and Humidity Index (BGHI) and Radiant Heat Load (RHL, W/m²) were calculated. ET (33.32 ± 0.12 °C), ST (36.10 ± 0.07 °C), OGT (37.40 ± 0.06 °C) and RT (38.83 ± 0.03 °C) differed significantly (P˂0.05). There was positive correlation of RT with OGT (r = 0.392), ET (r = 0.264) and ST (r = 0.236) (P˂0.05). Considering the bioclimatic indicators, the highest magnitude correlations were observed between ET and THI (r = 0.71), ET and BGHI (r = 0.65), and ET and RHL (r = 0.48). The use of microchip represented a practical method, but with limited predictability. On the other hand, infrared thermography proved to be safe and non-invasive, presenting greater precision for inference of internal body temperature. ET was more influenced by meteorological conditions.

The Impact of Heat Load on Cattle

Heat stress and cold stress have a negative influence on cattle welfare and productivity. There have been some studies investigating the influence of cold stress on cattle, however the emphasis within this review is the influence of heat stress on cattle. The impact of hot weather on cattle is of increasing importance due to the changing global environment. Heat stress is a worldwide phenomenon that is associated with reduced animal productivity and welfare, particularly during the summer months. Animal responses to their thermal environment are extremely varied, however, it is clear that the thermal environment influences the health, productivity, and welfare of cattle. Whilst knowledge continues to be developed, managing livestock to reduce the negative impact of hot climatic conditions remains somewhat challenging. This review provides an overview of the impact of heat stress on production and reproduction in bovines.

Land and Water Usage in Beef Production Systems

This analysis, using published data, compared all land and conserved water use in four beef production systems. A widespread feedlot system and fertilised irrigated pasture systems used similar amounts of land. However, extensive unmodified pasture systems used three times more land, and semi-intensive silvopastoral systems used four times less land, so the highest use was 13 times the lowest. The amount of conserved water used was 64% higher in feedlots with relatively intensive rearing systems than in fertilised irrigated pasture; in extensive unmodified pasture systems, it was 38% and in semi-intensive silvopastoral systems, it was 21% of the fertilised irrigated pasture value, so the highest use was eight times the lowest. If there was no irrigation of pasture or of plants used for cattle feed, the feedlot water use was 12% higher than the fertilised pasture use and 57% higher than that in semi-intensive silvopastoral systems. These large effects of systems on resource use indicate the need to consider all systems when referring to the impact of beef or other products on the global environment. Whilst the use of animals as human food should be reduced, herbivorous animals that consume food that humans cannot eat and are kept using sustainable systems are important for the future use of world resources.

Effect of heat ameliorative measures on microclimate, physiological, blood biochemical parameters and milk production in lactating Surti buffaloes

The present investigation was carried out to evaluate the effect of heat ameliorative measures (fans, foggers, green agro shadenet) on physiological, haematological, biochemical and milk production parameters in Surti buffaloes. Lactating Surti buffaloes (36) were equally divided into two groups and kept in two sheds. Group I animals were housed in a shed without any modification while Group II animals housed in a shed fitted with fans and foggers inside the shed and roof top white washed with microfine lime and open paddock was covered with green shade net and foggers were fitted. There were significant differences in the THI values of both inside and outside of the sheds at majority of periods during the hot-dry season. The floor and roof temperature of control shed at almost all-time intervals was significantly higher than the floor temperature of treatment shed. Significant difference in rectal temperature was observed at 14 and 28 days while respiration rate was significantly lower in animals of treatment shed. In treatment group, total erythrocyte count and haematocrit was significantly low at day 21 and mean platelet volume was significantly high at day 42. Significantly high levels of cholesterol, chloride and sodium at day 21 and glucose, protein, triglyceride, GSH, TAS and sodium at day 42 were observed in treatment group. Weekly milk yield (kg) during hot-dry season was significantly higher for treatment group than control group at 3rd, 4th and 5th weeks of the experiment. Evening milk yield of treatment group was significantly higher than the control and the cumulative milk yield (for 42 days) was also significantly higher for treatment group than control group (180.08 vs.150.80 kg). It can be concluded that microclimate modifications help in reducing heat stress and has beneficial effect on physiological responses, blood biochemical parameters and total milk production in lactating Surti buffaloes during hot dry season.

Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots

Formulating diets conservatively for minimum crude-protein (CP) requirements and overfeeding nitrogen (N) is commonplace in grain finishing rations in USA, Canada and Australia. Overfeeding N is considered to be a low-cost and low-risk (to cattle production and health) strategy and is becoming more commonplace in the US with the use of high-N ethanol by-products in finishing diets. However, loss of N from feedlot manure in the form of volatilised ammonia and nitrous oxide, and nitrate contamination of water are of significant environmental concern. Thus, there is a need to improve N-use efficiency of beef cattle production and reduce losses of N to the environment. The most effective approach is to lower N intake of animals through precision feeding, and the application of the metabolisable protein system, including its recent updates to estimation of N supply and recycling. Precision feeding of protein needs to account for variations in the production system, e.g. grain type, liveweight, maturity, use of hormonal growth promotants and β agonists. Opportunities to reduce total N fed to finishing cattle include oscillating supply of dietary CP and reducing supply of CP to better meet cattle requirements (phase feeding).

Effects of rumen-protected carbohydrate supplementation on performance and blood metabolites in feedlot finishing steers during heat stress

The objective of this experiment was to evaluate the inclusion of a rumen-protected carbohydrate (RPC) on growth performance and blood metabolites of finishing steers during the summer. A 62-d feedlot study was conducted using 135 Angus crossbred steers (body weight = 287 ± 13 kg). All animals were fed a basal diet (BD), then treatments were top-dressed. The treatments were the same composition and only varied in ruminal degradability. Treatments were 1) a BD with 1 kg/d of a control supplement (0RPC), 2) the BD plus 0.5 kg/d of the control supplement and 0.5 kg/d of RPC (0.5RCP), and 3) the BD with 1 kg/d of RPC supplement (1RPC). Temperature humidity index and cattle panting scores (CPS) were measured daily during the experiment. Growth performance, back-fat over the 12th rib (BF), LM area, blood glucose and plasma insulin, urea, and nonesterified fatty acid concentrations were measured. Data were statistically analyzed (PROC Mixed, SAS) using treatment, time, and their interaction as a fixed variable and pen as a random variable. There were no differences (P > 0.10) between the three treatments on CPS, BF, and LM area on day 62. There was a trend (P = 0.06) for treatment effect for a greater body weight on the 0.5RPC, and a treatment effect for dry matter intake (P = 0.05). Treatment × day interactions were observed for average daily gain (ADG, P =0.04), suggesting a different response to treatments during the different sampling periods. There was a treatment effect for blood glucose concentration (P = 0.03), having the 0RPC the greatest concentration. Treatment × day interactions were found for plasma insulin concentration (P = 0.01). The results suggest that the response to RPC supplementation depends in part on environment. The use of 0.5 kg/d of RPC tends to improve overall body weight; however, the response to RPC on ADG and plasma insulin concentration depend on the time of sampling.

Relationship between Rectal Temperature and Vaginal Temperature in Grazing Bos taurus Heifers

This study evaluated the relationship between rectal temperature (T_REC, °C) and vaginal temperature (T_VAG, °C) in grazing Bos taurus heifers, to develop an understanding of the reliability of these measures as estimates of core body temperature. Nineteen Angus heifers (BW = 232.2 ± 6.91 kg) were implanted with intra-rectal and intra-vaginal data loggers. Rectal temperature and T_VAG were simultaneously recorded at 20 s intervals over 18.5 h. Heifers were housed as a singular cohort on grazing pastures for the duration of the study. A strong linear relationship (R² = 0.72, p < 0.0001) between the measurement sites was identified. The mean difference between T_REC and T_VAG was small, in which T_VAG was on average 0.22 ± 0.01 °C lower than T_REC. Individual twenty second T_REC and T_VAG data were used to determine the pooled mean T_REC and T_VAG and then to highlight the within measure variation over time. The coefficient of variation was, on average, lower (p < 0.001) for T_VAG (0.38%) than T_REC (0.44%), indicating that T_VAG exhibited less variation. Overall, the results from the current study suggest that a strong relationship exists between T_REC and T_VAG, and that T_VAG may be a more reliable estimate of core body temperature than T_REC in grazing Bos taurus heifers.

Effect of modified housing on growth and physiological performance of crossbred dairy calves during the summer

The present study was conducted on crossbred (Vrindavani) cattle calves to evaluate the effect of modified housing using different roofing materials on growth and physiological performance of calves during the summer. Calves (24; 6–8 months old) were randomly selected and allocated in 4 groups, viz. control (C): corrugated cemented sheet (CCS) as roofing material, T1: the CCS roof was painted black inside and white outside, T2: polycarbonate plastic sheet as roof; and T3: polycarbonate roof with adjustable height. Overall the average temperature of shed was significantly lower in T1 (24.89±0.08) followed by T3 (27.30±0.10), T2 (28.28±0.04) and C (29.46±0.16). Overall average relative humidity (%) was significantly lower in T3 (62.38±0.30) as compared to T1 (64.54±0.14), T2 (65.68±0.23) and C (66.30±0.30). Overall average temperature humidity index was significantly lower in T1 (76.32±0.30) followed by T3 (76.50±0.16), T2 (77.91±0.05) and C (78.74±0.25). Total body wt gain (kg) was significantly higher in T3 (35.67), followed by T1 (34.83), T2 (34.1) and C (28.16). Overall rectal temperature (°C) and respiration rate (per minute) in afternoon was significantly higher in control as compared to all other treatment groups. It may be inferred that the micro-environment was more conducive in T1 and T3 than control; hence the reflective paints on roof and adjusted higher height of polycarbonate roof may be the desirable choice for animal housing in view of mitigating heat stress during the summer.

Review: Adaptation of ruminant livestock production systems to climate changes

There is growing evidence on the extent to which projected changes in climate, including increases in atmospheric levels of carbon dioxide, higher temperatures, changes in amount, seasonality and variability of precipitation and increases in extreme weather events, may affect future availability of ruminant animal products. Elements of climate change affect livestock systems through direct impacts on animal physiology, behaviour, production and welfare and indirectly through feed availability, composition and quality. These impacts may be positive or negative and will vary across geographical regions, animal species and with adaptive capacity. However, adverse impacts are likely to be greatest in tropical and sub-tropical regions including countries where both current need and future growth in demand for nutrition is greatest. The complexity of effects means that effective adaptation strategies to mitigate negative impacts on ruminant production systems to climate changes will need to be multi-dimensional. Although predictions of future climate, particularly on regional and local scales, have a degree of uncertainty, adaptation planning is starting to be informed by changes already being observed and adjustments in management being made by farmers to maintain productivity and profitability. Regional case studies illustrate the benefits and limitations of adaptive management: potential mitigation through heightened awareness of heat stress-related mortality in French cattle; evidence of a drop in milk production in south-eastern Australian dairies during a January 2014 heat wave, from the theoretical potential of 53% to only 10% across the state; and limitations in response options to climate-induced thermal, nutritional and water stress for sheep and goat farmers in northern Ethiopia. Review of research on climate change impacts on ruminant livestock and effective adaptation together with evidence of practical adaptive management provide insights into potential strategies and gaps in knowledge to address challenges and improve future decisions.

Effect of heat stress on rumen temperature of three breeds of cattle

Thirty-six steers (12 of each Angus, Charolais, and Brahman) with an initial BW of 318.5 ± 6.7 kg were used in a 130-day study. Two treatments were imposed: un-shaded and shaded (3 m²/animal; 90% solar block shade cloth). On day 1, steers were administered with rumen temperature boluses. Rumen temperatures (T _RUM) were obtained at 10 min intervals over the duration of the study to determine differences in T _RUM between Bos indicus and Bos taurus cattle. Six feedlot pens (162 m²) were used with six steers (2/breed) per pen with three pens/treatment. Ambient dry bulb temperature (T _A; °C), relative humidity (RH; %), wind speed (WS; m/s) and direction, and solar radiation (SR; W/m²) were recorded at 10 min intervals. Rainfall (mm) was collected daily at 0900 h. From these data, black globe temperature (BGT; °C), temperature humidity index (THI), heat load index (HLI), and accumulated heat load (AHL) were calculated. Individual T _RUM were converted to an hourly average and then mean hourly T _RUM were converted to a mean within hour T _RUM across the 130 days. Rumen temperatures were analyzed using an autoregressive repeated measures model. The model analyzed the effect of breed (P < 0.0002), treatment (P = 0.3543), time of day (hour, h; P < 0.0001), breed × treatment (P < 0.3683), breed × h (P < 0.0001), treatment × h (P < 0.0001), breed × treatment × h (P = 0.0029), pen within treatment (P = 0.0195), and animal × breed × treatment within pen (P = 0.1041). Furthermore, there were breed × treatment × hour differences in T _RUM (P = 0.0036), indicating that Bos indicus and Bos taurus regulate T _RUM differently.

Developing a heat load index for lactating dairy cows

The temperature humidity index (THI) has been extensively used in the Australian dairy industry as an indicator of heat load conditions. However, there are limitations to the THI, where it does not account for solar radiation or wind speed. In addition, the THI has not been formulated in conjunction with physiological data. Thus, it is not apparent whether the THI provides the best prediction for impact of heat load on lactating dairy cattle. The aim of the present study was to develop a dairy heat load index (DHLI), based on the physiological responses of lactating dairy cows to environmental conditions. The study was undertaken at The University of Queensland, Gatton Campus, Australia, over three summers and two winters. Observations were conducted four times daily at 0800 hours, 1200 hours, 1400 hours and 1700 hours. Weather data were obtained every 10 min from an onsite, automated weather station. Panting score data were used to calculate a mean panting score of the herd. Developing the DHLI encompassed three different modelling techniques, including (1) linear regression, (2) broken stick regression and (3) non-linear logistic regression. Comparisons between the models indicated there was an increase in accuracy when using non-linear logistic regression (R2 = 0.542). The DHLI model developed was based on mean panting score, black globe temperature (°C) and relative humidity. By utilising the black globe temperature, the DHLI is able to incorporate the combined effects of ambient temperature, relative humidity, solar radiation and wind speed in a single unit measure. By combining climatic conditions and a physiological response, i.e. panting score, the DHLI model may become a more accurate prediction of heat load for lactating dairy cows. The DHLI produces a unit value between 0 and 100. When DHLI is 0, there would be no panting and, when DHLI is 100, all cows within the herd would be panting.

Short communication: using infrared thermography as an in situ measure of core body temperature in lot-fed Angus steers

Thirty-six Black Angus steers were used in a replicated study; three replicates of 12 steers/replicate. Steers had an initial non-fasted BW of 392.3 ± 5.1, 427.5 ± 6.3, and 392.7 ± 3.7 kg for each replicate, respectively. Steers were housed outside in individual animal pens (10 m × 3.4 m). Each replicate was conducted over a 6-day period where infrared thermography (IRT) images were collected at 3-h intervals, commencing at 0600 h on day 1 and concluding at 0600 h on day 6. Rumen temperatures (T _RUM) were measured at 10-min intervals for the duration of each replicate using a radio-frequency identification (RFID) rumen bolus. These data were used to determine the relationship with surface temperature of the cattle, which was determined using IRT. Individual T _RUM were converted to an hourly average. The relationship between T _RUM and surface temperature was determined using Pearson's correlation coefficient. There were no linear trends between mean hourly T _RUM and mean surface temperature. Pearson's correlation coefficient indicated that there were weak associations (r ≤ 0.1; P < 0.003) between T _RUM and body surface temperature. These data suggest that there was little relationship between the surface temperature and T _RUM.

Evaluation of infrared thermography as a diagnostic tool to predict heat stress events in feedlot cattle

OBJECTIVE To determine whether infrared thermographic images obtained the morning after overnight heat abatement could be used as the basis for diagnostic algorithms to predict subsequent heat stress events in feedlot cattle exposed to high ambient temperatures. ANIMALS 60 crossbred beef heifers (mean ± SD body weight, 385.8 ± 20.3 kg). PROCEDURES Calves were housed in groups of 20 in 3 pens without any shade. During the 6 am and 3 pm hours on each of 10 days during a 14-day period when the daily ambient temperature was forecasted to be > 29.4°C, an investigator walked outside each pen and obtained profile digital thermal images of and assigned panting scores to calves near the periphery of the pen. Relationships between infrared thermographic data and panting scores were evaluated with artificial learning models. RESULTS Afternoon panting score was positively associated with morning but not afternoon thermographic data (body surface temperature). Evaluation of multiple artificial learning models indicated that morning body surface temperature was not an accurate predictor of an afternoon heat stress event, and thermographic data were of little predictive benefit, compared with morning and forecasted weather conditions. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated infrared thermography was an objective method to monitor beef calves for heat stress in research settings. However, thermographic data obtained in the morning did not accurately predict which calves would develop heat stress later in the day. The use of infrared thermography as a diagnostic tool for monitoring heat stress in feedlot cattle requires further investigation.

Measurement of bovine body and scrotal temperature using implanted temperature sensitive radio transmitters, data loggers and infrared thermography

Synchronous and continuous measurement of body (BT) and scrotal temperature (ST) without adverse welfare or behavioural interference is essential for understanding thermoregulation of the bull testis. This study compared three technologies for their efficacy for long-term measurement of the relationship between BT and ST by means of (1) temperature sensitive radio transmitters (RT), (2) data loggers (DL) and (3) infrared imaging (IRI). After an initial pilot study on two bulls to establish a surgical protocol, RTs and DLs were implanted into the flank and mid-scrotum of six Wagyu bulls for between 29 and 49 days. RT frequencies were scanned every 15 min, whilst DLs logged every 30 min. Infrared imaging of the body (flank) and scrotum of each bull was recorded hourly for one 24-h period and compared to RT and DL data. After a series of subsequent heat stress studies, bulls were castrated and testicular tissue samples processed for evidence of histopathology. Radio transmitters were less reliable than DLs; RTs lost >11 % of data, whilst 11 of the 12 DLs had 0 % data loss. IRI was only interpretable in 35.8 % of images recorded. Pearson correlations between DL and RT were strong for both BT (r > 0.94, P < 0.001) and ST (r > 0.80, P < 0.001). Surgery produced temporary minor inflammation and scrotal hematoma in two animals post-surgery. Whilst scar tissue was observed at all surgical sutured sites when bulls were castrated, there was no evidence of testicular adhesion and normal active spermatogenesis was observed in six of the eight implanted testicles. There was no significant correlation of IRI with either DL or RT. We conclude that DLs provided to be a reliable continuous source of data for synchronous measurement of BT and ST.

Effect of shade on animal welfare, growth performance, and carcass characteristics in large pens of beef cattle fed a beta agonist in a commercial feedlot

Feedlot cattle ( = 1,395; BW = 568 ± 43 kg) were used to evaluate the effects of shade on animal welfare, growth performance, and carcass quality during the summer of 2013 in a Kansas commercial feedlot. Seven lots of predominately black steers and heifers (4 and 3, respectively) visually determined to be approaching the final mo on feed were identified, randomly gate-sorted, and allocated to pens located across the feed alley from each other to receive 1 of 2 treatments: 1) Shade (mean shade area = 1.5 m/ animal) or 2) No shade. Shade was provided using a 13-ounce polyethylene fabric and pens were oriented northwest to southeast. The mean starting date was June 13 and the mean days on feed for lots while on the study was 38 d. Cattle were fed a 77.67% DM steam-flaked corn-based diet and had ad libitum access to water throughout the duration of the trial. Zilpaterol hydrochloride (ZIL) was included in the finishing ration at an inclusion rate of 8.3 mg/kg of DM for the last 20 d on feed with a 3 d withdrawal period. Pen floor temperatures (PFT) were measured using an infrared thermometer and prevalence of cattle open-mouth breathing (OMB) was recorded on a pen basis. In addition to shade treatment, the effect of temperature humidity index (THI) on PFT and OMB was analyzed by classifying days as either "Alert" (THI < 79) or "Danger" (THI > 79). On the day of slaughter, pens within a replicate were kept separate through all stages of the marketing channel from loading at the feedlot until stunning at the plant. Pen served as the experimental unit for all measurements. There was a THI × shade treatment interaction for PFT and OMB ( < 0.001) where days classified as "Danger" increased PFT and prevalence of OMB compared to "Alert" days in unshaded but not shaded cattle. Shaded cattle had greater DMI ( = 0.01); however, unshaded cattle had greater G:F ( = 0.05) and therefore no differences were observed in ADG ( = 0.39). Shaded cattle had greater dressing percentage ( = 0.01), although HCW, LM area, fat thickness, marbling score, and quality grade did not differ between treatments ( > 0.05). Heat stress, a significant animal welfare concern and cause of reduced performance in feedlot cattle during the final phase of the feeding period, was alleviated in shaded cattle and illustrates the importance of shade provision as 1 tool to protect the welfare and increase feed consumption in large pens of feedlot cattle during hot summer months.

Physiological responses of feedlot heifers provided access to different levels of shade

Heat stress has a significant impact on all livestock and poultry species causing economic losses and animal well-being concerns. Providing shade is one heat-abatement strategy that has been studied for years. Material selected to provide shade for animals greatly influences the overall stress reduction provided by shade. A study was conducted to quantify both the environment and animal response, when cattle had no shade access during summertime exposure or were given access to shade provided by three different materials. A total of 32 Black Angus heifers were assigned to one of the four treatment pens according to weight (eight animals per pen). Each pen was assigned a shade treatment: No Shade, Snow Fence, 60% Aluminet Shade Cloth and 100% Shade Cloth. In the shaded treatment pens, the shade structure covered ~40% of the pen (7.5 m2/animal). Animals were moved to a different treatment every 2 weeks in a 4×4 Latin square design to ensure each treatment was applied to each group of animals. Both environmental parameters and physiological responses were measured during the experiment. Environmental parameters included dry-bulb temperature, relative humidity, wind speed, black globe temperature (BGT), solar radiation (SR) and feedlot surface temperature. Animal response measurements included manual respiration rate (RRm), electronic respiration rate (RRe), vaginal temperature (body temperature (BT)), complete blood count (CBC) and plasma cortisol. The environmental data demonstrated changes proportional to the quality of shade offered. However, the animal responses did not follow this same trend. Some of the data suggest that any amount of shade was beneficial to the animals. However, Snow Fence may not offer adequate protection to reduce BT. For some of the parameters (BT, CBC and cortisol), 60% Aluminet and 100% Shade Cloth offers similar protection. The 60% Aluminet lowered RRe the most during extreme conditions. When considering all parameters, environmental and physiological, 60% Aluminet Shade Cloth offered reductions of BGT, SR, feedlot surface temperature and the best (or equal to the best) overall protection for the animals (RRe, RRm, BT, blood parameters).

Evaluation of the welfare of cattle housed in outdoor feedlot pens

The use of open outdoor feedlots for housing large numbers of cattle is increasing in many parts of the world. In these systems cattle are kept in large outdoor pens on a soil surface. One major welfare concern associated with this type of housing is keeping cattle clean and preventing muddy conditions. If the annual rainfall exceeds 20 in (51 cm). It is more difficult to keep the surface dry. In dry parts of the world with low rainfall, it is much easier to keep cattle clean and dry. Another issue is heat stress, and there are warmer parts of the world where shade may be required. The third issue is handling and vaccinating large numbers of cattle. In the U.S. this is an area where conditions have improved because management is now more aware about animal welfare. There are three major outcome based measurements that should be used to assess cattle welfare in open feedlots. They are: scoring of hide cleanliness, panting scoring for heat stress and numerical scoring of cattle handling practices.

Modelling enteric methane abatement from earlier mating of dairy heifers in subtropical Australia by improving diet quality

Milking cows typically dominate dairy farm greenhouse gas (GHG) emissions, but replacement heifers also contribute to farm emissions and can increase the emission intensity of milk production. In northern Australia, heifers generally graze poorer-quality subtropical pastures and in the absence of energy-dense supplementary feed during periods of low pasture growth, liveweight (LW) gain can be restricted. This modelling study examined the time required and enteric methane (CH4) emissions produced in raising dairy heifers to a target LW for first mating by feeding a diet assuming either constant (static) or variable (dynamic) nutritive values. Using a static approach (Australian Feeding Standards methodology), and assuming a target mating LW of 360 kg, growing heifers reached their target LW at ~18 months of age while consuming C4 grasses with a constant metabolisable energy content of 9.5 MJ/kg dry matter (DM) or 11 months of age on a diet of 11.0 MJ/kg DM. Enteric CH4 emissions were 1.2 and 0.8 t of carbon dioxide equivalents/heifer over the 18- and 11-month periods, respectively. To explore the extent with which climatic conditions influence seasonal pasture availability and nutritive value with a dynamic approach, we used a whole-farm biophysical model (SGS pasture model) to simulate diets with mean metabolisable energy values of 9.5 and 10.9 MJ/ kg DM. On average (±s.d.), heifers required 22 ± 4 and 17 ± 1 months, respectively, to reach target LW, with cumulative enteric CH4 emissions of 1.22 ± 0.20 and 0.72 ± 0.04 t carbon dioxide equivalents, respectively. The dynamic approach resulted in slower LW gain due to the variable nutritive value of the diet throughout the year, resulting in seasonal periods of LW plateauing or decline. Maintaining heifers on high-quality diets in subtropical northern Australia should result in increased daily LW gain, lower enteric CH4 emissions to mating LW and earlier calving. Together, these factors reduce their lifetime emission intensity of milk production.

Shade use by small groups of domestic horses in a hot, sunny environment

Horses in the United States are commonly managed in outside pens or pastures in small groups. Limited research on shade use by domestic horses housed singly in individual pens has shown benefits and a preference for using available shade. The objective of this study was to examine the amount of shade use and the behavioral and physiological responses of small groups of horses when housed with access to shade (SH) and without access to shade (SUN). Thirty-six horses were randomized into 3 consecutive trials using 3 horses per group and 4 groups per trial. Groups experienced 5 d in each treatment in a crossover design. Weather factors were measured with automated sensors 24 h/d throughout the study. The mean afternoon ambient temperature was 31.0°C with relative humidity of 32%. Rectal temperature, respiration rate, and skin temperature were recorded at 1000, 1330, and 1900 h daily. Venous blood samples were obtained on Days 0 and 5 to measure serum cortisol, the neutrophil:lymphocyte ratio, and hematocrit. Behavioral observations for presence in shade, standing near or away from water, locomotion, and foraging were recorded at 5-min intervals from 1400 to 1900 h daily. Insect avoidance behaviors were recorded hourly during that same time period for 1 min/horse. Horses in the SH treatment were observed using shade in 7.1% of observations between 1400 and 1900 h, and behavioral differences were observed between the SH and SUN treatments. When in the SUN treatment, horses stood near the water troughs more (18.5 vs. 14.2% of observations; = 0.029) and foraged less (29.3 vs. 33.8% of observations; < 0.001) than when in the SH treatment. There were no treatment differences for other behaviors or for physiological measures ( > 0.05). Provision of shade structures accessible to groups of mature, healthy horses in hot, sunny environments should be considered in developing future guidelines for best management practices for horses.