The present experiment was aimed to investigate, the correlation between temperature humidity index (THI) and skin surface temperature (Ts) at different thermal windows of the body and to find the ameliorative effect of chromium picolinate (CrPiC3) supplementation on Ts during heat exposure in buffalo. The healthy male buffaloes were randomly allotted into three groups NHS (ambient control), HS (heat stressed) and HSC (heat stressed + CrPiC3 supplemented). Both pre- and post-exposure Ts on head, neck, ear, forelimb, flank and hind limb were recorded on days 0, 6, 11, 16, 21 and post-recovery (seven days after last heat exposure) with the help of infra-red digital thermometer. Statistical analysis showed (P<0.05) increase in Ts at all regions of the body in HS in comparison to NHS group. In addition, CrPiC3 supplementation showed the ameliorative effect by decreasing (P<0.05) Ts at different studied areas in HSC than HS group. It was found that THI and Ts of all surface areas were positively correlated with the highest correlation with hind limb Ts. It could be concluded that supplementation of diet with CrPiC3 during the period of heat stress improves the heat tolerance capability in buffaloes by decreasing Ts.
In homeotherms, the body temperature remains fairly constant and fluctuates within relatively narrow limits. To maintain the body temperature, there is a constant exchange of heat between animal and the environment (Junior et al., 2010). During adverse climatic conditions, cutaneous and respiratory heat dissipation plays a predominant role in adaptation and to maintain physiological body temperature (Gebremedhin and Wu, 2001). Although, tympanic and rectal temperature are the frequently been used as a measure of core body temperature, yet the change in body temperature can be measured by recording temperature at body extremities, as they are the main locations for regulating heat loss or storage (Heuvel et al., 2004). Collier et al., 2008) have considered measuring skin surface temperature (Ts) as an alternative method for measuring radiant environmental temperature. The infrared thermography (IRT) is a non-invasive evaluation technique aid in the precocious diagnosis of affections (Yadav et al., 2017) and plays a crucial role in measuring Ts. It also helps in evaluating the response of animals to the environmental changes and differentiating between genetic groups (Paim et al., 2013).
Chromium (Cr) has been recognized as an essential trace mineral and found to alleviate stress associated effects in human (Anderson, 1994), broiler chicken (Sand and Smith, 1999), cattle (Qiang et al., 2009) and buffaloes (Kumar et al., 2015). Compounds with organic Cr can be absorbed 20-30 times more efficiently than inorganic forms (Pechova and Pavlata, 2007). Most of the buffalo diets are composed of plant ingredients which are low in Cr. Therefore, during heat stress buffaloes are more prone to Cr scarcity. Since, very limited data available for the use of IRT for evaluation of heat stress, therefore, the present study was designed to evaluate the effects of dietary organic Cr supplementation on Ts and to study THI and Ts correlation.
Material and Method
The Site of an Experiment
The present study was carried out at the Psychrometric Chamber, Division of Physiology and Climatology, IVRI, Bareilly, U.P., India. Location of this institute is 28°39′N and 79°43′E having a sub-tropical climate. The experiment was conducted in the month of November 2015 to January 2016, when mean THI was 68.81. Temperature and humidity of both ambient control and the psychrometric chamber were monitored throughout the experimental period and THI was calculated (Tucker et al., 2008).
THI = (1.8 × AT + 32) – [(0.55 – 0.0055 × RH) × (1.8 × AT – 26)]
where, AT = air temperature, °C, and RH = relative humidity %.
Animals and Experimental Design
Eighteen healthy male buffaloes (Bubalus bubalis) of uniform age (1.5-2 years) and weighing ~222 Kg were selected for the present study. The animals were maintained under the proper managemental condition with ad lib feed and water. Animals were randomly allotted into 3 groups (n= 6 in each group) 1: NHS (non-heat stressed group as ambient control i.e. thermal comfort natural environment control) maintained in the experimental shed throughout the study. 2: HS (Heat stressed group) and 3: HSC (heat stressed supplemented with 1.5 mg/Kg DMI Chromium picolinate). Both HS and HSC are subjected to daily 6 h (10:00 am to 4:00 pm) heat exposure at 40ºC for 21 days inside a psychrometric chamber (7.5×7.5×2.5 m3) insulated and thermostatically fitted heat convector. Before exposing animals to heat stress, they were kept inside the natural climate room adjoining to the psychrometric chamber for six days for acclimatization. Ts at the head, ear, neck, forelimb, flank and hind limb were taken by using the non-invasive infra-red digital thermometer (ebro® TFI220) from 6-inch distance without disturbing animal before and after heat exposure on day 0, 6, 11, 16, 21 and on day 28 as recovery.
Data were statistically analyzed by one-way analysis of variance (ANOVA) followed by Tukey’s-b multiple range tests, using SAS 9.3 (SPSS Inc., Chicago, IL, USA). Pearson’s correlation was employed in the analysis of the relationships between the THI and Ts. The data was presented as bars and expressed as Mean ± SEM.
Result and Discussion
Thermal Environmental Data Recorded during the Study Period
THI, it’s a product of temperature and relative humidity and is invariably been use for assessment of level of heat stress in animals. It is well known that environmental temperature affects Ts (Arp et al., 1983). In present study to observe supplementation effect of CrPiC3 on Ts, animals were artificially exposed to heat stress under closed psychometric chamber with the temperature of 40 ºC and relative humidity of 35% with mean THI of animal microenvironment was 87.56 for both HS and HSC. The THI values >75 indicate that the animals would be under mild stress conditions compared thermal comfort zone if taken as the frame of reference the interpretation that THI ≤74 is considered ideal for raising buffalo (Somparn et al., 2004). In contrast, it was demonstrated that buffalo did not show sign of heat stress or reduction of growth performance when THI was between 73.5 and 82.2 (Junior et al., 2010) or when THI varied from 75.0 to 81.0 (Garcia et al., 2011). This suggests that the microclimatic conditions (THI: 87.56) in the psychrometric chamber of the present study were unfavorable and posed a significant threat to the thermoregulatory mechanisms of the buffaloes as the sign of heat stress was apparent.
Ts of Buffalo during Heat Stress between Groups and Within the Groups
Ts of the head, neck, ear, forelimb, flank and hind limb and correlation between mean THI and Mean Ts during the study period are shown in Figure 1-6 and Table 1, respectively. The meteorological elements, air temperature, air humidity, the wind and solar radiation impinge on the surface of the animal and affect the production and reproduction. These factors affecting the receptors present on the skin and sends information to brain sets into compensatory action like the change in the rate of heat dissipation mechanism, blood circulation, respiration and skin thickness (Hafez, 1968).
Table 1: Correlation coefficient among THI and Ts of buffalo during heat stress
** (P<0.01), * (P<0.05)
In present study pre-exposure, Ts of all areas of the skin surface of buffalo were significantly (P<0.05) higher in HS than NHS on day six, thereafter, their values were comparable with other groups, it may be due to acute exposure to heat and later it got adopted on subsequent sampling period. After heat exposure, Ts of all body parts of buffalo were significantly (P<0.05) higher in HS than NHS. Homeotherms, however, constantly produce heat and lose it to the environment, so that there is a thermal gradient from warm core to the less warm surface of the body (Hafez, 1968). The blood vessel in the skin dilated during hot summer to bring core body heat to skin for dissipation by radiation and convection (Bianca, 1965). The change in skin Ts not only varies in relation to exposure but also due to water diffusion and evaporation from the skin.
In HS group, pre-exposure Ts of all body parts were in their zenith on day six. Similarly on day zero and eleven during post-exposure, the Ts was higher (P<0.05) than other days at all the surface areas studied. The rise and fall of Ts of all body surface areas during post-exposure showed same trend in decreasing order: neck (Fig: 2. Mean Ts: 93.62°F) > hindlimb (Fig: 6. Average Ts: 93.45°F) > and forelimb (Fig: 4. Mean Ts: 91.90°F) > head (Fig: 1. Average Ts: 91.30°F) > flank (Fig: 5. Average Ts: 90.50°F) > ear (Fig: 3. Mean Ts: 87.97°F). Das et al., 1999, observed increase in Ts with increased in intensity of solar radiation with the mean Ts of forehead (20.09°C), forelimb (18.5°C), ear (18.21°C) were higher than neck (13.09°C) and hind leg (15.84°C) when exposed to solar radiation during summer in buffaloes calve.
In HSC group, there was a significant decrease in Ts both pre and post-exposure than HS, indicates ameliorative effects of chromium supplementation. The proposed mechanism of ameliorative effect may be due to increased excretion of Cr during heat stress which results in depletion of body chromium stores (Pechova and Pavlata, 2007). Moreover, exogenous Cr supplementation gets reduce to trivalent Cr by gastric juice as explained by Doisy et al., 2013, which is a biologically active part of an oligopeptide–chromodulin potentiating the effect of insulin by facilitating insulin binding to receptors at the cell surface (Vincent, 2000).
Therefore, it increases glucose uptake and production of glycogen by liver cell by increasing insulin sensitivity. Hence, plasma glucose level and its availability to the muscle cell for heat production get decreases, which intern decreases the metabolic heat production. Reduced heat production decreases the thermal gradient between surface and core body temperature. This results in decreased peripheral blood supply leading to lowering Ts. However, Kumar et al., 2015 showed that chromium supplementation has no significant effect on physiological responses in summer exposed buffaloes calves.
Significantly (P<0.01) positive correlations of mean Ts of all body area studied and mean THI observed along with, Ts between each other. Among the correlations observed between mean THI and mean Ts of different regions, the most significant (P<0.01) were between THI and hind limb, (0.716; P<0.01), THI and head (0.524; P<0.01) and THI and neck (0.514; P<0.01).
The Ts were elevated and significantly (P<0.01) correlated after 6 h heat exposure in HS and HSC groups. However, the increment in Ts was less in HSC group as compared to HS group. Hence, CrPiC3 supplementation may have ameliorative effect in buffalo during heat stress.
The above work is supported by NICRA project entitled “Adaptation strategies in livestock to thermal stress through nutritional and environmental manipulations”.
Conflict of Interest
Neither authors nor their close relatives have financial Interest or arrangement with pharmaceutical companies, bio medical device manufacturers, or other corporations related to the products or methods used.