Hydration state of goats transported by road for 12 hours during the hot-dry conditions and the modulating role of ascorbic acid

This study investigated the effects of 12 hr of road transportation during the hot-dry conditions and the modulating role of ascorbic acid (AA) on the hydration state of goats. Twenty goats who served as treatment goats received oral administration of 100 mg/kg body weight of AA, whereas another 20 control goats received sterile water; thereafter, the goats were loaded and transported. The study determined changes in skin thickness; albumin (Alb); total protein (TP); elimination of the gut content; fecal water; urine specific gravity (SG); and pH before, during, and after the transportation. The result obtained in the control goats showed significant (p < .05) increases in the values of TP, Alb, urine SG, and pH; elimination; and drinking behavior, whereas skin thickness decreased over transportation. In the treatment goats who were administered AA, the changes observed in the values were insignificant (p > .05). In conclusion, 12-hr road transportation of goats induced dehydration, which may affect the welfare and health status of the goats. The administration of AA ameliorated the risk of adverse effects of handling, loading, transportation, and hot-dry conditions on hydration state of goats.     

Critical THI thresholds based on the physiological parameters of lactating dairy cows

The severity of heat stress conditions in high-yielding dairy cows is currently underestimated. The present study aimed to determine the heat load threshold of the temperature-humidity index (THI) on physiological parameters of lactating Holstein-Friesian cows under a continental climatic zone in Germany. Physiological parameter measurements, such as respiration rate (RR), measured hourly, and heart rate (HR) and rectal temperature (RT), both measured twice daily, were performed in a total of 139 multiparous cows on three randomly chosen measurement days per week. In addition, the ambient temperature and relative humidity of the barn were recorded every 5 min to calculate the current THI. The physiological parameter data were linked to the THI, and the heat load thresholds were determined using the broken-stick model. The heat load duration effect of each physiological parameter was obtained by regression analysis. Considering the increases in the physiological parameters, our study provided reliable data to determine heat load thresholds for lactating high-yielding dairy cows in a moderate climatic zone. The heat load threshold could be determined for RR in standing cows (THI = 70) and lying cows (THI = 65) and for HR (THI = 72) and RT (THI = 70) in standing cows. The heat load duration also demonstrated a significant effect on the increases in physiological parameters among dairy cows. In particular, the present study enabled a strategy to be devised to initiate heat mitigation in high-yielding dairy cows when they are exposed to THIs above 65.     

Hydration State of Goats Transported by Road for 12 Hours During the Hot-Dry Conditions and the Modulating Role of Ascorbic Acid

This study investigated the effects of 12 hr of road transportation during the hot-dry conditions and the modulating role of ascorbic acid (AA) on the hydration state of goats. Twenty goats who served as treatment goats received oral administration of 100 mg/kg body weight of AA, whereas another 20 control goats received sterile water; thereafter, the goats were loaded and transported. The study determined changes in skin thickness; albumin (Alb); total protein (TP); elimination of the gut content; fecal water; urine specific gravity (SG); and pH before, during, and after the transportation. The result obtained in the control goats showed significant (p < .05) increases in the values of TP, Alb, urine SG, and pH; elimination; and drinking behavior, whereas skin thickness decreased over transportation. In the treatment goats who were administered AA, the changes observed in the values were insignificant (p > .05). In conclusion, 12-hr road transportation of goats induced dehydration, which may affect the welfare and health status of the goats. The administration of AA ameliorated the risk of adverse effects of handling, loading, transportation, and hot-dry conditions on hydration state of goats.     

Pineal–adrenal–immune system relationship under thermal stress: effect on physiological,endocrine, and non-specific immune response in goats

The purpose of the investigation was to observe the pineal–adrenal–immune system relationships and their influence on non-specific immune response in female goats under short-term thermal stress. Six female goats had been exposed to 40°C and 60% relative humidity in the psychrometric chamber for 17 days. Blood samples were obtained on days 0 and 10 to establish control and thermal stress effects, respectively. Chemical adrenalectomy was achieved by injecting metyrapone (100 mg/kg body weight) followed by exogenous melatonin treatment (0.1 mg/kg body weight) from 11th to 17th day of experiment. Thermal stress significantly (P ≤ 0.05) altered the physiological responses. Metyrapone and melatonin treatment significantly (P ≤ 0.05) reduced the thermal-stress-induced increase in plasma concentrations of cortisol and corticosterone while significantly (P ≤ 0.05) increased the plasma melatonin on days 11 and 17. Furthermore, these treatments significantly (P < 0.05) increased the phagocytic activity of neutrophils as compared to both control and thermal exposure values from 11–17 days of experiment. The data generated from this study help us to understand the functional relationship between pineal, adrenal, and immune system, and how this relationship modifies the non-specific immune response for the well being of goats during thermal stress.     

Impact of air pollution control measures and weather conditions on asthma during the 2008 Summer Olympic Games in Beijing

The alternative transportation strategy implemented during the 2008 Summer Olympic Games in Beijing provided an opportunity to study the impact of the control measures and weather conditions on air quality and asthma morbidity. An ecological study compared the 41 days of the Olympic Games (8 August–17 September 2008) to a baseline period (1–30 June). Also, in order to emphasize the impact of weather conditions on air quality, a pollution linking meteorological index (Plam) was introduced to represent the air pollution meteorological condition. Our study showed that the average number of outpatient visits for asthma was 12.5 per day at baseline and 7.3 per day during the Olympics—a 41.6% overall decrease. Compared with the baseline, the Games were associated with a significant reduction in asthma visits (RR 0.58, 95%CI: 0.52–0.65). At 16.5 visits per day, asthma visits were also significantly higher, during the pre-Olympic period (RR 1.32, 95% CI: 1.15–1.52). The study also showed that the RR of asthma events on a given day, as well as the average daily peak ozone concentration during the preceding 48–72 h, increased at cumulative ozone concentrations of 70 to 100 ppb and 100 ppb or more compared with ozone concentrations of less than 70 ppb (P < 0.05). We concluded that along with “good” weather conditions, efforts to reduce traffic congestion in Beijing during the Olympic Games were associated with a prolonged reduction in air pollution and significantly lower rates of adult asthma events. These data provide support for efforts to reduce air pollution and improve health via reductions in motor vehicle traffic.     

Evaluation of adaptability to different seasons in goat breeds of semi-arid region in India through differential expression pattern of heat shock protein genes

The present study was conducted to examine differential expression pattern of HSP genes and adaptability in Indian goat breeds of semi-arid region. The study was conducted in five animals from each breed viz. Barbari, Sirohi, and Jhakrana during winter, thermo-neutral and summer seasons. The respiratory rate (RR) and rectal temperature (RT) of the goats were recorded at 09:00 h during the study period. The blood samples were collected for RNA isolation, cDNA synthesis, and quantitative analysis of HSP genes expression by quantitative RT-PCR. The RR increased significantly (p < 0.01) during summer as compared to winter and thermo-neutral season however, RT did not change (p > 0.05) during different seasons. The expression of HSP genes was significantly (p < 0.01) increased during summer (high THI) as compared to thermo-neutral season in all the goat breeds. Among HSPs, only HSP90 was upregulated (p < 0.01) in Jhakrana goats during winter as compared to thermo-neutral season. The deviation in expression of HSP genes during summer and winter with respect to thermo-neutral season was minimum in Barbari goats. Therefore, it can be concluded that Barbari goats possessed better adaptability during summer and winter as compared to Sirohi and Jhakrana goats in semi-arid climatic conditions of India.     

The influence of thermal conditions on rectal temperature,respiration rate and pulse rate of lactating Holstein-Friesian cows in the humid tropics

The effect of minimum, maximum and mean ambient air temperatures and the temperature-humidity index (THI) of the same and the previous day on morning (a.m.) and afternoon (p.m.) rectal temperatures (RT), respiration rates (RR) and pulse rates (PR) were studied in 17 Holstein-Friesian cows over the first 125 days in the 3rd and 4th lactations. Physiological responses showed a diurnal pattern, being lower in the mornings than the afternoons: 38.6 vs 39.0° C for RT, 52.2 vs 60.7 breaths/min for RR and 58.1 vs 64.1 beats/min for PR. Correlations between RT and RR (r = – 0.043 to –0.046) and RT and PR (r = –0.178 to –0.261) were low (P> 0.05). Correlations between RR and PR (r = 0.353 to 0.365) were moderate (P<0.05). Weather variables, especially ambient temperature of the previous day, were more important and influenced physiological responses to a greater extent than other thermal factors the same day. Generally, physiological responses were influenced to a greater extent by ambient temperature than THI. Weather variables explained variations in RT (5.1–59.6%), in RR (13.0–17.8%) and in PR (22.1–25.4%). Relationships between weather variables the previous day and physiological responses were contradictory, with minimum and maximum values showing a negative relationship in contrast with a positive relationship for mean values.     

Effect of hot temperatures on the hematological parameters,health and performance of calves

The objective of this paper was to evaluate the effects of high temperatures on calves. The hypothesis that the red and white blood cells, health, and performance of calves would be influenced by the temperature period at birth and gender was tested. Sixty-three Holstein calves were used. They were reared in individual hutches from the second day of life to weaning at the age of 8 weeks. All calves were allotted to treatment groups according to the temperature period at birth: moderate temperature period 1 (MT1), high temperature period (HT), moderate temperature period 2 (MT2). The same conditions of nutrition were ensured. We recorded 62 summer days and 14 tropical days during HT. Sixty-six days with a value above 72.0 of the temperature–humidity index (THI) and 26 with values greater than 78.0 were found. No significant differences were found in red blood cells with the exception of hemoglobin between MT1 and MT2 (p = 0.031) during the 8th week. Significant differences were observed among treatment groups in the percentage of eosinophiles during the 6th week (p  = 0.044). The HT calves had the least body weight from the first week to weaning (p = 0.053) and the highest water consumption (p = 0.042). The results emphasize the ability of dairy calves to maintain homeostasis during prolonged periods of heat stress. The exposure to high temperatures resulted only in a significant decrease of starter concentrate consumption and reduced growth.     

Improvement of thermal comfort indices in agroforestry systems in the southern Brazilian Amazon

Agroforestry systems can minimize heat stress and improve cattle welfare, but the influence of the forest component in microclimatic changes in the southern Amazon remains unclear. This study aimed to compare the thermal comfort indices in grass monoculture and integrated systems. The three systems were pasture under full sunlight (PFS), integrated (triple-row) livestock-forestry (ILF_T), and integrated (single-row) livestock-forestry (ILFs), across four seasons, for two years, from June 2017 to June 2019. We assessed photosynthetically active radiation (PAR), air temperature, relative humidity, black globe temperature, and wind speed. Thermal comfort indices such as temperature-humidity index (THI), black globe temperature-humidity index (BGHI), and radiant thermal load (RTL) were calculated based on microclimate data daily-collected from 8:00 to 16:00. The ILF_T mean THI (76.8) was slightly lower than ILF_S and PFS. The BGHI and RTL values decreased as shading increased (PFS > ILFs > ILF_T). The most challenging heat stress conditions for grazing animals occurred predominately during winter and autumn. In conclusion, the presence of trees in pastures of the southern Amazon improved the microclimate and, consequently, the thermal comfort indices. Agroforestry systems can foster an environment with a more suitable thermal comfort or less restrictive to animal performance, which contribute to mitigating global climate change for forage-livestock systems in Brazilian Amazon.     

Effect of induced transportation stress in goats supplemented with vitamin C and jaggery during hot dry season

The objective of current study was to investigate the effect of induced transportation stress in goats and to seek a novel approach to minimize the transportation and seasonal effect on the physiology of goats by supplementing them with Vitamin C and Jaggery before transportation. Fifty goats were selected and divided into five groups with ten animals in each group. Group 1 served as negative control and was neither supplemented nor transported, while as goats in groups 2 to group 5 were transported for 10 hours on the day of transportation. Group 2 goats were not supplemented; group 3 goats were supplemented with Vitamin C @180 mg/kg body weight/day; group 4 goats were supplemented with jaggery @200g/day/animal; group 5 was supplemented with both vitamin C and jaggery for 5 days before transportation. Effect of transportation stress varied significantly among groups in terms of haematological, biochemical, hormonal, mineral and blood gas parameters. Transportation up to 10 hours induced stress in goats during hot dry season as represented by changes in different physiological parameters and body weight shrinkages. Supplementation of Vitamin C and Jaggery aided in reducing transportation stress individually, with variable effects on stress response parameters and there combination synergistically proved promising in alleviating transportation stress in goats.     

Physiological and electroencephalogram responses in goats subjected to pre-and during slaughter stress

A comprehensive stress assessment is vital in understanding the impact of the pre-slaughter procedure on animal welfare. The transportation and handling process was commonly reported to cause stress in animals. This research utilises electroencephalography (EEG) as an alternative stress indicator to non-painful acute stress measurement. EEG has been proved to be instantaneous and sensitive with specific results. Therefore, this study was aimed to determine the stress level of goats subjected to two different transportation duration and the effect of lairage based on their EEG activities and blood parameters changes. Eighteen adult male goats were divided into two transportation stress groups based on the transport duration: the two-hour (TS2) and six-hour (TS6) groups. Then, each group was then again divided into three smaller groups according to the lairage duration, which was three-hour (L3), six-hour (L6), and overnight (L12) groups. Blood was sampled before transport, after transport, and during slaughter while EEG was recorded before transport, after transport, after lairage, and during slaughter. Results revealed that there was a significant decrease in beta wave activity compared to baseline in TS2 goats (P < 0.05) after transportation, whereas no significant difference was detected in the TS6 goats. At the same time, goats from the TS2 group showed increase in creatine kinase (CK) and lactate dehydrogenase (LDH) compared to that in TS6 goats. Together with the observed cortisol concentration, these findings showed that the TS6 goats were fully adapted to the transportation stress while the TS2 goats were still under stress. As for the lairage duration, it was observed that the TS2L3 goats showed lower EEG activities than the values obtained after two-hour transportation, while lower EEG activities were found from the TS6L6 goats after six-hour transportation. Therefore, it can be concluded that three-hour lairage was adequate to lower the impact of two hours transportation stress, whereas six-hour lairage was required to reduce the impact of six hours transportation stress. Finally, it was also found that the TS6L3, TS6L6, and TS6L12 groups took a long time to die after slaughter than the TS2L3, TS2L6, and TS2L12 goats based on the time their EEG activity reached isoelectric.     

Adaptive capability as indicated by endocrine and biochemical responses of Malpura ewes subjected to combined stresses (thermal and nutritional) in a semi-arid tropical environment

A study was conducted to assess the effect of combined stresses (thermal and nutritional) on endocrine and biochemical responses in Malpura ewes. Twenty eight adult Malpura ewes (average body weight 33.56 kg) were used in the present study. The ewes were divided into four groups viz., GI (n = 7; control), GII (n = 7; thermal stress), GIII (n = 7; nutritional stress) and GIV (n = 7; combined stress). The animals were stall fed with a diet consisting of 60% roughage and 40% concentrate. GI and GII ewes were provided with ad libitum feeding while GIII and GIV ewes were provided with restricted feed (30% intake of GI ewes) to induce nutritional stress. GII and GIV ewes were kept in climatic chamber at 40°C and 55% RH for 6 h a day between 1000 hours and 1600 hours to induce thermal stress. The study was conducted for a period of two estrus cycles. The parameters studied were Hb, PCV, glucose, total protein, total cholesterol, ACP, ALP, cortisol, T₄, T₃, and insulin. Combined stress significantly (P < 0.05) affected all parameters studied. Furthermore, the results revealed that, compared to thermal stress, nutritional stress had a less significant effect on the parameters studied. However, when both these stresses were coupled, they had a severe impact on all the parameters studied in these ewes. It can be concluded from this study that two stressors occurring simultaneously may impact severely on the biological functions necessary to maintain homeostasis in sheep.     

Effect of sprinkling on feedlot microclimate and cattle behavior

Experiments were conducted to evaluate strategies designed to reduce heat stress of cattle. In the first experiment, cattle were sprinkled for 20 min every 1.5 h between 1000 hours and 1750 hours (WET) versus not sprinkled (DRY). In a second experiment, treatments consisted of: (1) control, no water application; (2) water applied to the pen surfaces between 1000 hours and 1200 hours (AM); and (3) water applied to pen surfaces between 1400 hours and 1600 hours (PM). In both experiments, sprinkling lowered (P < 0.05) mid-afternoon temperatures. In the first experiment, relative humidity (RH) of WET versus DRY pens differed (P < 0.05) and averaged 72.4 and 68.9%, respectively. The average temperature–humidity index (THI) in WET pens was 0.5 units lower (P < 0.05), than the THI in DRY pens. In the second experiment, RH in sprinkled pens was also greater (P < 0.05) than RH in control (CON) pens However, THI differed (P < 0.05) among treatments, being 81.5, 80.9, and 80.3, respectively for CON, AM, and PM. Pens with sprinklers had a larger percentage of steers in areas where sprinkling took place, even on days when sprinkling had not occurred. Based on differences in percentage of cattle panting in sprinkled and non-sprinkled treatments, sprinkling was found to have a positive effect on cattle feeding area microclimate and to reduce the susceptibility of cattle to hyperthermia. However, cattle acclimatization to being sprinkled can result in slight hyperthermia even during cooler days when sprinkling would normally not be utilized.     

Impact of heat stress on conception rate of dairy cows in the moderate climate considering different temperature–humidity index thresholds,periods relative to breeding,and heat load indices

The objectives of this retrospective study were to investigate the relationship between temperature–humidity index (THI) and conception rate (CR) of lactating dairy cows, to estimate a threshold for this relationship, and to identify periods of exposure to heat stress relative to breeding in an area of moderate climate. In addition, we compared three different heat load indices related to CR: mean THI, maximum THI, and number of hours above the mean THI threshold. The THI threshold for the influence of heat stress on CR was 73. It was statistically chosen based on the observed relationship between the mean THI at the day of breeding and the resulting CR. Negative effects of heat stress, however, were already apparent at lower levels of THI, and 1 hour of mean THI of 73 or more decreased the CR significantly. The CR of lactating dairy cows was negatively affected by heat stress both before and after the day of breeding. The greatest negative impact of heat stress on CR was observed 21 to 1 day before breeding. When the mean THI was 73 or more in this period, CR decreased from 31% to 12%. Compared with the average maximum THI and the total number of hours above a threshold of more than or 9 hours, the mean THI was the most sensitive heat load index relating to CR. These results indicate that the CR of dairy cows raised in the moderate climates is highly affected by heat stress.     

Alterations in Electrocardiographic Parameters after Subacute Exposure of Fluoride and Ameliorative Action of Aluminium Sulphate in Goats

Fluorosis or crippling disease is one of the existing environmental challenges for animal and human beings in most parts of the globe. In the present study, sodium fluoride alone and with aluminium sulphate (ameliorative agent) was administered orally daily for 30 days in healthy goats of group 1 and 2, respectively, to access the effect on the electrocardiogram. All waves of Lead I, Lead II, Lead III, aVR, aVL and aVF in electrocardiographs were recorded before and after 30 days exposure of fluoride. A significant (P < 0.05) increase in P–R, Q–T and S–T intervals were observed in goats of group 1 as compared to their pre treatment values. The T wave duration was also significantly (P < 0.05) prolonged and as a result, bradycardia was observed after subacute exposure of fluoride for 30 days in group 1. But, in group 2, no such changes were observed. On the basis of results, it may be concluded that subacute toxicity of fluoride produces significant changes in different waves of electrocardiogram and aluminium sulphate has ameliorative efficacy.     

Performance Traits and Metabolic Responses in Goats (<Emphasis Type="Italic">Capra hircus)</Emphasis> Supplemented with Inorganic Trivalent Chromium

The effects of supplemental chromium (Cr) as chromic chloride hexahydrate in incremental dose levels (0, 0.5, 1.0, and 1.5 mg/day for 240 days) on metabolism of nutrients and trace elements were determined in dwarf Bengal goats (Capra hircus, castrated males, average age 3 months, n = 24, initial mean body weight 6.4 ± 0.22 kg). Live weight increased linearly (p < 0.05) with the level of supplemental Cr. Organic matter and crude protein digestibility, intake of total digestible nutrients, and retention of N (g/g N intake) increased (p < 0.05) in a dose-dependent linear manner. Serum cholesterol and tryacylglycerol concentrations changed inversely with the dose of supplemental Cr (p < 0.01). Supplemental Cr positively influenced retention of copper and iron (p < 0.05) causing linear increase (p < 0.01) in their serum concentrations. It was concluded that Cr supplementation may improve utilization of nutrients including the trace elements and may also elicit a hypolidemic effect in goats. However, further study with regards to optimization of dose is warranted.     

Effect of walking stress on growth,physiological adaptability and endocrine responses in Malpura ewes in a semi-arid tropical environment

Sheep in hot semi-arid environments are mostly reared using extensive systems. In addition to thermal stress and feed scarcity, the animals need to walk long distances for grazing in this ecological zone. A study was conducted to assess the effect of long-distance walking on adaptive capability in terms of physiological, biochemical and endocrine responses in Malpura ewes. Fourteen adult Malpura non-pregnant ewes weighing between 33 and 35 kg were used in the study. The ewes were randomly allocated into two groups of seven animals each: GI (n = 7; Control), and GII (n = 7; walking stress). The animals were stall-fed with a diet consisting of 70% roughage and 30% concentrate. Both GI and GII ewes had uniform access to feed and water. The walking stress group (GII) ewes were made to walk 14 km in two spans between 0900 and 1500 hours with 1 h 30 min for each span (7 km) of walking. The ewes subjected to walking stress (GII) were prevented from grazing by applying a face mask made of cotton thread. The study was conducted for a period of two estrous cycles (35 days) during the autumn season (October–November). Physiological responses were recorded twice daily at 0800 and 1400 hours at weekly intervals. Blood samples were collected from the jugular vein at weekly intervals to study the effects of walking stress on blood biochemical and endocrine parameters. The results indicate that walking stress had significant (P < 0.05) influence on body weight, average daily gain, respiration rate (RR), rectal temperature (RT), haemoglobin (Hb), packed cell volume (PCV), plasma glucose, calcium, phosphorus, aspartate amino transferase (AST), alanine amino transferase (ALT), tri-iodo-thyronine (T₃), thyroxin (T₄), and cortisol. However, walking stress did not influence the reproductive hormone levels. The significant changes in RR, RT, plasma cortisol, T₃ and T₄ show that Malpura ewes have the capability to adapt to long-distance walking, and that adrenal and thyroid gland hormones play a significant role in such adaptation.     

Determinants of bovine thermal response to heat and solar radiation exposures in a field environment

Continuous exposure of cattle to summer heat in the absence of shade results in significant hyperthermia and impairs growth and general health. Reliable predictors of heat strain are needed to identify this condition. A 12-day study was conducted during a moderate summer heat period using 12 Angus x Simmental (Bos taurus) steers (533 ± 12 kg average body weight) to identify animal and ambient determinations of core body temperature (T _core) and respiration rate (RR) responses to heat stress. Steers were provided standard diet and water ad libitum, and implanted intraperitoneally with telemetric transmitters to monitor T _core hourly. Visual count of flank movement at 0800 and 1500 hours was used for RR. Dataloggers recorded air temperature (T _a), and black globe temperatures (T _bg) hourly to assess radiant heat load. Analysis was across four periods and 2 consecutive days averaged within each period. Average T _a and T _bg increased progressively from 21.7 to 30.3°C and 25.3 to 34.0°C, respectively, from the first to fourth periods. A model utilizing a quadratic function of T _a explained the most variation in T _core (R ² = 0.56). A delay in response from 1 to 3 h did not significantly improve R ² for this relationship. Measurements at 0800 and 1500 hours alone are sufficient to predict heat strain. Daily minimum core body temperature and initial 2-h rise in T _a were predictors of maximum core temperature and RR. Further studies using continuous monitoring are needed to expand prediction of heat stress impact under different conditions.     

Daily rumination time of lactating dairy cows under heat stress conditions

The dairy industry in regions with moderate climates, such as Central Europe, will be increasingly challenged in the future by climate change. The problem of heat stress will especially affect dairy husbandry in naturally ventilated barns (NVB). The approach of the study was to determine a heat stress threshold of the average daily temperature-humidity index (THI) that results in changes in the daily rumination time (RT) of lactating, high-yielding cows. The data set was composed of a high sample size of 183 cows and long-duration measurements of 21240 daily observations over two years from June 2015 to May 2017, which were collected in an NVB in Groβ Kreutz, Germany. The THI was calculated in 5-min intervals by data from several sensors in different positions inside the barn. Additionally, every cow from the herd of an average of 53 cows in the experimental procedure was wearing a neck collar with a Lely Qwes HR system that provided the RT 24 h a day (12 2-h recordings were summarized). The study showed that heat stress also negatively influenced RT in moderate climates. The heat stress threshold of 52 THI was determined by broken-stick regression and indicated changes of RT of lactating dairy cows in Germany. During the experimental period, the heat stress threshold for RT was reached from April to September for up to 720 h per month. The changes in RT to the heat stress threshold will be affected by cows' characteristics. Therefore, we considered several cow-related factors, such as milk yield (MY), lactation number (LN), lactation stage (days in milk, or DIM) and pregnancy stage (P) to better understand cows’ individual reactions to heat stress. Multiparous, high-yielding cows in later lactation stages are potentially more strongly affected than other cows.     

Alternative body sites for heat stress measurement in milking cows under tropical conditions and their relationship to the thermal discomfort of the animals

This study was conducted to determine the relationship among temperatures measured at different anatomical sites of the animal body and their daily pattern as indicative of the thermal stress in lactating dairy cows under tropical conditions. Environmental dry bulb (DBT) and black globe (BGT) temperatures and relative humidity (RH) were recorded. Rectal temperature (RT), respiratory frequency (RF), body surface (BST), internal base of tail (TT), vulva (VT) and auricular temperatures (AT) were collected, from 37 Black and White Holstein cows at 0700, 1300 and 1800 hours. RT showed a moderately and positive correlations with all body temperatures, ranging from 0.59 with TT to 0.64 with BST. Correlations among AT, VT and TT with RF were very similar (from 0.63 to 0.64) and were greater than those observed for RF with RT (0.55) or with BST (0.54). RF and RT were positively correlated to TT (0.63 and 0.59, respectively), AT (r = 0.63 for both) and VT (r = 0.64 and 0.63, respectively). Positive and very high correlations were observed among AT, VT and TT (from 0.94 to 0.97) indicating good association of temperatures measured in these anatomical sites. Correlations of BST with AT and VT were positive and very similar (0.71 and 0.72, respectively) and lower with TT (0.66). The AT, TT, VT and BST presented similar patterns and follow the variations of DBT through the day. Temperatures measured at different anatomical sites of the animal body have the potential to be used as indicative of the thermal stress in lactating dairy cows.