Comparative assessment of climate resilient potential in four poultry genotypes reared in hot-humid tropical environment: a preliminary evaluation.

The general objective of this study is to comparatively assess the climate-resilient potential of four different poultry genotypes-Giriraja (n = 8), Country chicken (n = 8), Naked neck (n = 8), and Kadaknath (n = 8)-reared in a hot-humid tropical environment. Birds from all genotypes had ad libitum access to feed and water and were exposed to identical environmental temperatures in the experimental shed. Diurnal meteorological data were recorded inside and outside the shed daily. Blood biochemical, hormonal, and endocrine variables were monitored monthly until the birds reached 12 weeks of age. Significant variations (P < 0.01) were observed at different intervals in variables, including total protein, albumin, globulin, triglycerides, and cholesterol. Genotype-specific differences were noted in triglycerides (P < 0.01), albumin (P < 0.01), total protein (P < 0.05), and cholesterol (P < 0.05). Inter-genotype variations (P < 0.05) were also observed in serum cortisol, T3, and T4 levels. Distinct variations (P < 0.05) were also observed during specific intervals, particularly in cortisol and T3 levels. The study of hepatic mRNA expression of HSPs and HSF-1 revealed a significant breed difference (P < 0.05) in the expression pattern of HSP60, HSP70, HSP90, and HSP110, while no difference was observed between genotypes for HSP40 and HSF-1. The study highlights the Naked Neck breed as an exemplar of resilience, showcasing its distinctive ability to maintain homeostasis under heat stress compared to other genotypes. The genetic and physiological insights gained from this investigation offer prospective pathways for aligning sustainable poultry farming with environmental exigencies.

Do newborn lambs with black and white hair-coats in an equatorial semi-arid environment maintain homeothermy?

We assessed newborn lambs from two hair-coat sheep breeds, the black Santa Ines (n = 29) and white Dorper (n = 26), to determine how they behaviourally and physiologically respond to the prevailing thermal conditions in an equatorial semi-arid environment. Measurements of hair-coat surface temperature, rectal temperature and the lambs' exposure to sun were recorded across the first 24 h of life every hour, after the lambs had received colostrum. Lambs and ewes were kept in a lambing pen and could freely move between a shaded area or be exposed to sun. During the study period, the air temperature ranged between 20 ºC and 34 ºC. When exposed to sun, lambs and ewes could experience as much as 1200 W m-2 of solar irradiance. Santa Ines lambs exhibited higher (highest density interval at 95%, HDI) hair-coat surface temperatures than did Dorper lambs. Overall, both Santa Ines and Dorper lambs sustained homeothermy, with a mean rectal temperature ranging from 38.7 ºC to 39.1 ºC between night and daytime phase, and a mean amplitude of ~ 0.8 ºC. Nevertheless, from 10:00 to 15:00, some lambs were found to be moderately hyperthermic. Five Santa Ines and three Dorper lambs had rectal temperatures above 40 ºC, and one Santa Ines lamb, while exposed to sun, had a rectal temperature of 41.3 ºC. Over this time period, lambs were more likely to move to shade (HDI at 95%). From 00:00 to 06:00, despite the air temperature being lower than the hair-coat surface, favouring high rates of sensible heat loss to the environment, no lamb exhibited signs of hypothermia (rectal temperature < 37.5 ºC). In conclusion, haired newborn lambs coped well with high levels of radiant heat during the daytime and lower temperatures at night. However, providing access to shade during the daytime is important to improve the welfare of newborn lambs delivered in equatorial semi-arid regions.

Comparative assessment of growth performance, heat resistance and carcass traits in four poultry genotypes reared in hot-humid tropical environment.

This study investigated the impact of heat stress on growth and carcass traits in four poultry genotypes-Giriraja, Country chicken, Naked Neck and Kadaknath reared in a hot and humid tropical environment. Birds from all genotypes had ad libitum access to feed and water while being challenged with consistently high environmental temperatures in the experimental shed. Daily diurnal meteorological data were recorded inside and outside the shed. The study specifically examined growth variables and carcass characteristics. Significant differences (p < 0.01) were observed in body weight and average daily gain at various intervals. Notably, feed intake showed significant differences (p < 0.01) across weeks, indicating interactions between genotypes and time intervals. The feed conversion ratio (FCR) varied significantly (p < 0.01), with the highest FCR recorded in the Kadaknath breed. Livability percentages were similar across groups, except for Giriraja, which had significantly lower livability (p < 0.01). Carcass traits, including dressing, wings, feathers and giblet percentages, showed significant differences among genotypes (p < 0.01). Hepatic mRNA expression of growth-related genes revealed numerical variations, with Naked Neck displaying the highest (p < 0.05) fold change in IGF-1 expression compared to other genotypes. The study recognized in the Naked Neck genotype to possess higher resilience in maintaining homoeostasis and uncompromised growth under heat stress, providing valuable insights for sustainable poultry farming in challenging environmental conditions.

Comparing the responses of grain-fed feedlot cattle under moderate heat load and during subsequent recovery with those of feed-restricted thermoneutral counterparts: blood cells and inflammatory markers.

Given the climate projections for livestock rearing regions globally, understanding the inflammatory status of livestock under various heat loads will be informative to animal welfare and management. A survey of plasma inflammatory markers was conducted, and blood leucocyte counts followed to investigate the capacity of the ~ 500 kg grain fed Black Angus steer to respond to and recover from a moderate heat load challenge. Two sequential cohorts of 12 steers were housed in climate-controlled rooms (CCR) for 18 days. A thermally challenged (TC) group (n = 2 × 6) experienced five consecutive periods: PreChallenge, Challenge, and Recovery within the CCR, and 40 days in outdoor pens (PENS and Late PENS). PreChallenge (5 days) and Recovery (7 days) delivered thermoneutral conditions, whereas in Challenge the TC steers experienced a diurnal temperature range of 28-35 °C. A feed-restricted thermoneutral (FRTN) treatment (n = 2 × 6) was run concurrently to differentiate between responses to reduced feed intake alone and moderate heat stress. Blood neutrophil counts were particularly sensitive to moderate heat load with higher numbers during Challlenge and in PENs. The plasma concentrations of TNFα and IL-1ß were depressed in the TC group compared to the FRTN counterparts and remained so for 40 days after Challenge. Linear relationships of the concentrations of IL-1ß, IL-10, and haptoglobin with rumen temperature or dry matter intake detected in the FRTN group were altered or absent in the TC group. The findings suggest significant impacts of moderate heat load on the inflammatory status of feedlot cattle.

Comparative assessment of growth performance of indigenous and cross-bred calves subjected to combined stressors (heat and nutritional).

This study evaluated the impact of combined stressors (heat and nutritional stresses) on the growth and adaptive capability of Sahiwal (SW) and Karan Fries (KF) calves during the summer season. Calves in each breed were randomly divided into four groups. In SW breed the groupings were as follows: SWC (n = 4; Sahiwal Control); SWHS (n = 4; Sahiwal Heat Stress); SWNS (n = 4; Sahiwal Nutritional Stress) and SWCS (n = 4; Sahiwal Combined Stresses). Likewise, in the KF breed, KFC (n = 4; Karan Fries Control); KFHS (n = 4; Karan Fries Heat Stress); KFNS (n = 4; Karan Fries Nutritional Stress), and KFCS (n = 4; Karan Fries Combined Stresses). Control (C) and Heat Stress (HS) calves were fed ad libitum while Nutritional Stress (NS) and Combined Stresses (CS) calves were fed restricted feed (50% of C calves of respective breed) to induce nutritional stress in both the breeds. SWHS, SWCS, KFHS, and KFCS were exposed to summer heat stress from 1000 to 1600 h. All growth and adaptation variables were recorded at fortnightly intervals. Respiration rate, pulse rate, and rectal temperature during the afternoon were significantly (P < 0.01) higher in the CS group in both breeds. Further, CS had significantly (P < 0.05) higher plasma growth hormone and cortisol levels. Insulin-like growth factor-1, Triiodothyronine, and Thyroxine levels significantly decreased (P < 0.05) in the CS group in both breeds. Interestingly, heat stress didn't affect SWHS and KFHS bodyweight, however, a significant (P < 0.05) decrease in body weight of SWCS and KFCS was observed when compared with C. Hepatic mRNA expression of growth hormone, insulin-like growth factor-1, and growth hormone receptor significantly (P < 0.05) varied when compared between C and CS groups in both the breeds. The overall magnitude of stress was more pronounced in KF compared to the SW breed. This study concludes that when two stressors occur concurrently, they may have a greater influence on the adaptive capability of calves. Further, SW had better tolerance levels than KF, confirming the indigenous breed's superiority over cross-bred.

Diversity of rumen microbiota using metagenome sequencing and methane yield in Indian sheep fed on straw and concentrate diet.

An in vivo study aiming to investigate the rumen methanogens community structure was conducted in Mandya sheep fed on straw and concentrate diet. The ruminal fluid samples were collected and processed for unravelling the rumen microbiota and methanogens diversity. Further, the daily enteric methane emission and methane yield was also quantified using the SF6 tracer technique. Results indicated that the Bacteroidetes (∼57%) and Firmicutes (25%) were two prominent affiliates of the bacterial community. Archaea represented about 2.5% of the ruminal microbiota. Methanobacteriales affiliated methanogens were the most prevalent in sheep rumen. The study inveterate that the ruminal archaea community in sheep is composed of 9 genera and 18 species. Methanobrevibacter represented the largest genus of the archaeome, while methylotrophs genera constituted only 13% of the community. Methanobrevibacter gottschalkii was the prominent methanogen, and Methaobrevibacter ruminantium distributed at a lower frequency (∼2.5%). Among Methanomassiliicoccales, Group 12 sp. ISO4-H5 constituted the most considerable fraction (∼11%). KEGG reference pathway for methane metabolism indicated the formation of methane through hydrogenotrophic and methylotrophic pathways, whereas the acetoclastic pathway was not functional in sheep. The enteric methane emission and methane yield was 19.7 g/d and 20.8 g/kg DMI, respectively. Various species of Methanobrevibacter were differently correlated, and the distribution of hydrogenotrophic methanogens mainly explained the variability in methane yield between the individual sheep. It can be inferred from the study that the hydrogenotrophic methanogens dominate the rumen archaeal community in sheep and methylotrophic/aceticlastic methanogens represent a minor fraction of the community. Further studies are warranted for establishing the metabolic association between the prevalent hydrogenotrophs and methylotrophs to identify the key reaction for reducing methane emission.

Comparison of enteric methane yield and diversity of ruminal methanogens in cattle and buffaloes fed on the same diet.

An in vivo study was conducted to compare the enteric methane emissions and diversity of ruminal methanogens in cattle and buffaloes kept in the same environment and fed on the same diet. Six cattle and six buffaloes were fed on a similar diet comprising Napier (Pennisetum purpureum) green grass and concentrate in 70:30. After 90 days of feeding, the daily enteric methane emissions were quantified by using the SF6 technique and ruminal fluid samples from animals were collected for the diversity analysis. The daily enteric methane emissions were significantly greater in cattle as compared to buffaloes; however, methane yields were not different between the two species. Methanogens were ranked at different taxonomic levels against the Rumen and Intestinal Methanogen-Database. The archaeal communities in both host species were dominated by the phylum Euryarchaeota; however, Crenarchaeota represented <1% of the total archaea. Methanogens affiliated with Methanobacteriales were most prominent and their proportion did not differ between the two hosts. Methanomicrobiales and Methanomassillicoccales constituted the second largest group of methanogens in cattle and buffaloes, respectively. Methanocellales (Methanocella arvoryza) were exclusively detected in the buffaloes. At the species level, Methanobrevibacter gottschalkii had the highest abundance (55-57%) in both the host species. The relative abundance of Methanobrevibacter wolinii between the two hosts differed significantly. Methanosarcinales, the acetoclastic methanogens were significantly greater in cattle than the buffaloes. It is concluded that the ruminal methane yield in cattle and buffaloes fed on the same diet did not differ. With the diet used in this study, there was a limited influence (<3.5%) of the host on the structure of the ruminal archaea community at the species level. Therefore, the methane mitigation strategies developed in either of the hosts should be effective in the other. Further studies are warranted to reveal the conjunctive effect of diet and geographical locations with the host on ruminal archaea community composition.

Goat as the ideal climate-resilient animal model in tropical environment: revisiting advantages over other livestock species.

In the agriculture sector, livestock are considered extremely resilient to climate change and are tipped to play a significant role in ensuring food security to meet the increased demands of growing human population by 2050. Compared to other domestic species, goats are considered the ideal animal model for climate change due to its high thermal and drought resilience, ability to survive on limited pastures, and high disease resistance. This review is therefore a revisit to the advantages of rearing goats over other livestock species under current and future trends of changes in climate, particularly to cope with recurrent multiple stressors such as heat load, and lack of water and feed. In summary, goats, also called as poor man's cow, are preferred by the small-scale landless farmers due to their low input and assured higher output system, as they require low initial investment, with minimum specialized facilities and labors. Furthermore, they perceive goats as better resilient animal to cope with multiple stressors such as heat load, and water and feed scarcity, and possess better skills to cope with bush, when compared with sheep and cattle. The unique capacity for employing behavioral plasticity and morphological features of goats gives them clear advantage over sheep and cattle, when coping with seasonal biotopes, and experiences of water and feed shortage. When facing with low-quality feed, they also are superior to cattle and sheep to digest dry matter and to recycle nitrogen. Additionally, goats have superior ability to desiccate feces and concentrate urine, when compared with sheep and cattle. These advantages make goat the go-to species for efficiently countering the adversities associated with climate change and to optimize appropriate economic return through sustained production. Therefore, goats are tipped to be the future animals with extreme potential to counter the projected alarming climate change impacts and expected to play a significant role in ensuring food security to meet the demands of the growing human population by the end of this century.

Exploration of plant products and phytochemicals against aflatoxin toxicity in broiler chicken production: Present status.

Aflatoxins (AFs) are a class of mycotoxins produced by the toxigenic Aspergillus fungi and are common contaminants of foods and feeds. Aflatoxin B1 (AFB1), the most potent aflatoxin, is well characterized to reduce productive performance and mortality in broilers. This exclusive review summarizes the efficacy of various plant products and phytochemicals to counteract AFB1 toxicity in broilers. The biochemical and molecular mode of action of AFB1 to induce liver damage, genotoxicity, immunosuppression and the protective effect of plant products against such mechanisms and their toxic effects are discussed. The link between antioxidant, immunomodulatory and hepatoprotective functions of plant products; oxidative stress and AFB1 macromolecular adducts mediated AFB1 toxicity are covered. Efficacy of Satureja khuzistanica, Zataria multiflora Boiss, Thymus vulgaris, Sauropsus androgynus, Hemidesmus indicus, Leucas aspera, Moringa oleifera, Eclipta alba, Curcuma longa, Silybum marianum, Urtica dioica, and citrus fruit are summarized. The anti-aflatoxic effect of water-soluble substances of wheat, grape seed proanthocyanidin extract and phytochemicals like thymol, carvarol, piperine, transcinnamaldehyde, resveratrol, curcumin, and silymarin are also discussed. Specific plant products and phytochemicals are shown to be effective against AF toxicity in broilers and could represent an important tool to reduce health and economic losses associated with AFB1 exposure.

Analysis of carcass traits and quantitative expression patterns of different meat quality governing genes during heat stress exposure in indigenous goats.

A study was conducted to assess the impact of heat stress on various carcass traits, meat quality variables and gene expression patterns which governs meat quality in indigenous female Kodi Aadu breed. The study was conducted for 45 days in climate chamber with 12 animals randomly allocated into two groups of six animals each, KC (n = 6; Female; Control), KHS (n = 6; Female; heat stress). Majority of the major carcass traits and meat quality variables remained intact between KC and KHS groups. The myostatin (MSTN), calpain 1 (CAPN1) and Diacylglycerol Acyltransferase 1 (DGAT1) mRNA expression patterns were significantly (P < 0.01) lower in KHS group as compared to KC group. However, the calpain 2 (CAPN2), calpastatin (CAST) and Crytallin alpha (CRYA) mRNA expression patterns were significantly (P < 0.05) higher in KHS group. Thus, the study established that the major carcass traits and meat quality variables remained intact after heat stress exposure in female Kodi Aadu goats. Further, MSTN, HSP27, CRYA and HSP90 genes were identified as biomarkers for reflecting meat quality during heat stress exposure in female Kodi Aadu breed.

Heat stress and poultry production: impact and amelioration.

Globally, the poultry industry is gaining significant importance among the agricultural and its allied sectors. However, heat stress was found to negatively affect the poultry production particularly in the tropical regions. This review is therefore an attempt to generate information pertaining to the impacts of heat stress on poultry production and its amelioration. Heat stress reduces the growth, reproductive performance, and egg production in poultry birds. The reduction in productive potential of poultry birds on exposure to heat stress may be attributed to the deviation of energy resources from production to adaptation pathway. There are different approaches pertaining to relieving the adverse impacts of heat stress on poultry production. These approaches can be broadly categorized under genetic, management, and nutritional strategies. These approaches may reduce the negative effects of heat stress and enhance the productive performance of poultry birds. The management strategies include appropriate shelter design, providing shade, using sprinklers, implementing cooling devices, and using fans and ventilation systems. The recommended floor space for mature birds weighing 1.7 kg is 0.06 m2/bird while it is 0.13 m2/bird for the birds weighing 3.5 kg with 27.8 kg/m2 bird density in either case. The nutritional interventions comprise ration balancing and providing essential micronutrients to improve the productive and reproductive performance in poultry birds. Fat, antioxidants, yeast, and electrolyte supplementations are some of the most commonly used nutritional strategies to ensure optimum production in the poultry industry. Furthermore, providing adequate water supply and disease surveillance measures may help to ensure optimum meat and egg production in the birds. The advanced biotechnological tools may aid to identify suitable genetic markers in poultry birds which might help in developing new strains of higher thermo-tolerance by designing suitable breeding program involving marker-assisted selection. These strategies may help to optimize and sustain poultry production in the changing climate scenario.

Summer season induced changes in quantitative expression patterns of different heat shock response genes in Salem black goats.

Research efforts of elucidating the molecular mechanisms governing heat shock response which imparts thermo-tolerance ability to indigenous breeds are very scanty. Therefore, a study was conducted with the primary objective to determine the impact of heat stress on the expression pattern of different heat shock response genes in the hepatic tissues of indigenous Salem Black goat. The study was conducted for a period of 45 days in twelve 1-year-old female Salem Black breed goats. The animals were randomly allocated into two groups of six animals each, C (n = 6; Salem Black control) and HS (n = 6; Salem Black heat stress). The C animals were maintained in the shed in comfort condition while HS animals were exposed outside to summer heat stress between 10:00 h to 16:00 h during experimental period. The animals were slaughtered at the end of study and their liver samples were collected for assessing the different heat shock response genes. Based on the results obtained from the study it was established that the heat shock protein 70 (HSP70), HSP90, super oxide dismutase (SOD), nitrous oxide synthase 1 (NOS1) genes were significantly (P < 0.05) down regulated. However, heat stress did not influence the expression pattern of heat shock factor-1 (HSF1) gene. The lower level of expression of all heat shock response genes may be due to less magnitude of heat stress in the study to induce cellular stress response in Salem Black goats.

The impact of heat stress on the immune system in dairy cattle: A review.

Heat stress is well documented to have a negative influence on livestock productivity and these impacts may be exacerbated by climate change. Dairy cattle can be more vulnerable to the negative effects of heat stress as these adverse impacts may be more profound during pregnancy and lactation. New emerging diseases are usually linked to a positive relationship with climate change and the survival of microrganisms and/or their vectors. These diseases may exaggerate the immune suppression associated with the immune suppressive effect of heat stress that is mediated by the hypothalamic-pituitary-adrenal (HPA) and the sympathetic-adrenal-medullary (SAM) axes. It has been established that heat stress has a negative impact on the immune system via cell mediated and humoral immune responses. Heat stress activates the HPA axis and increases peripheral levels of glucocorticoids subsequently suppressing the synthesis and release of cytokines. Heat stress has been reported to induce increased blood cortisol concentrations which have been shown to inhibit the production of cytokines such as interleukin-4 (IL-4), IL-5, IL-6, IL-12, interferon γ (IFNγ), and tumor necrosis factor-α (TNF- α). The impact of heat stress on the immune responses of dairy cows could be mediated by developing appropriate amelioration strategies through nutritional interventions and cooling management. In addition, improving current animal selection methods and the development of climate resilient breeds may support the sustainability of livestock production systems into the future.

Prediction models, assessment methodologies and biotechnological tools to quantify heat stress response in ruminant livestock.

Livestock industries have an important role in ensuring global food security. This review discusses the importance of quantifying the heat stress response of ruminants, with an emphasis on identifying thermo-tolerant breeds. There are numerous heat stress prediction models that have attempted to quantify the response of ruminant livestock to hot climatic conditions. This review highlights the importance of investigating prediction models beyond the temperature-humidity index (THI). Furthermore, this review highlights the importance of incorporating other climatic variables when developing prediction indices to ensure the accurate prediction of heat stress in ruminants. Prediction models, particularly the heat load index (HLI) were developed to overcome the limitations of the THI by incorporating ambient temperature (AT), relative humidity (RH), solar radiation (SR) and wind speed (WS). Furthermore refinements to existing prediction models have been undertaken to account for the interactions between climatic variables and physiological traits of livestock. Specifically, studies have investigated the relationships between coat characteristics, respiration rate (RR), body temperature (BT), sweating rate, vasodilation, body weight (BW), body condition score (BCS), fatness and feed intake with climatic conditions. While advancements in prediction models have been occurring, there has also been substantial advancement in the methodologies used to quantify animal responses to heat stress. The most recent development in this field is the application of radio frequency identification (RFID) technology to record animal behaviour and various physiological responses. Rumen temperature measurements using rumen boluses and skin temperature recording using infrared thermography (IRT) are making inroads to redefine the quantification of the heat stress response of ruminants. Further, this review describes several advanced biotechnological tools that can be used to identify climate resilient breeds of ruminant livestock.

Heat stress impact on the expression patterns of different reproduction related genes in Malabari goats.

A study was conducted to evaluate the effect of heat stress on the expression pattern of reproduction related genes in Malabari breed of goat. The study was conducted during 45 days using twelve 10 months to one year old Malabari goats. The goats were randomly allocated into two groups: MC (n = 6; Malabari control) and MHS (n = 6; Malabari heat stress). Goats were stall-fed with a diet composed of 60% roughage and 40% concentrate. All animals had access to ad-libitum feed and water and they were fed and watered individually. The MC goats were placed in the shaded pens while MHS goats were exposed to heat stress in outside environment between 10.00 h and 16.00 h. At the end of study period, all 12 animals were slaughtered and their uterus tissues were collected for gene expression and histopathological studies. The temperature humidity index (THI) inside shed (74.9) proved that the animals were not stressed while in the outside environment (86.5) the animals were extremely distressed. Heat stress significantly (P < 0.05) influenced the expression patterns of follicle stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR), estrogen receptor α (ESTRα), prostaglandin F2 α (PGF2α) and cyclooxygenase-2 (COX-2). However, prostaglandin E2 (PGE2) did not differed between the groups. Further, a strong positive correlation (P < 0.01) was established for THI with both FSHR gene expression. A negative correlation was also established between THI and ESTRα (P < 0.01), PGF2α (P < 0.01), PGE2 (P < 0.05) genes. However, heat stress did not influence the expression patterns of LHR; COX-2 genes. The histopathological section of uterine epithelial cells showed degenerative changes (P < 0.05) with less differentiation in MHS group as compared to MC group. The results from the study clearly indicated that heat stress was able to alter the reproductive activity related gene expressions at uterine level and this could be an indication of reduced reproductive efficiency in Malabari goats.

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 (TREC) and rumen temperature (TRUM) and to assess if TRUM could be used as a proxy measure of core body temperature (TCORE) 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 TRUM as an estimation of TCORE, TREC 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 (TA; °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 TRUM data were converted to an individual hourly average. Pooled mean hourly TRUM data from the 128-day data were used to establish the diurnal rhythm of TRUM 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 TRUM and TREC using both real-time (r = 0.55; P < 0.001) and hourly mean (r = 0.51; P < 0.001) TRUM data. The mean difference between TREC and TRUM was small using both real-time (0.16 ± 0.02 °C) and hourly mean TRUM (0.13 ± 0.02 °C) data. Data from this study supports the hypothesis that TRUM can be used as an estimate of TCORE, suggesting that TRUM can be used to measure and quantify heat load in feedlot cattle.

Effect of heat stress on the quantitative expression patterns of different cytokine genes in Malabari goats.

A study was conducted to determine the influence of exposure to hot environment on different cytokine gene expression patterns in Malabari goat. The study was conducted in 12 (10 months to 1 year old) goats of Malabari breed for 45-day duration. The control (n = 6; C) group goats were kept under comfortable condition in the shaded pens while heat stress (n = 6; HS) group goats were kept out in the open hot environment during summer season for the study duration between 10.00 h to 16.00 h. The representative mesenteric lymph node (MLN) samples were collected from the slaughtered goats at the end of study for assessing the different cytokine gene expression and histopathological changes. Compared with C group, the expression patterns of interleukin 18 (IL-18), tumor necrosis factor-α (TNF-α), interferon-ß (IFN-ß), and IFN-γ downregulated (P < 0.05) in the HS group. The histopathological changes of MLNs showed paucity of lymphocyte distribution in follicular areas as wells as decreased density of lymphocytes in the germinal centers of the HS group (P < 0.05). The findings from this study reflected the compromised immune functions during heat stress in Malabari goats. Further, the study established that IL-18, TNF-α, IFN-ß, and IFN-γ genes could serve as reliable immunological markers for quantifying heat stress-mediated immune response alterations in Malabari goats.

Expression patterns of candidate genes reflecting the growth performance of goats subjected to heat stress.

The study is an attempt to elucidate the molecular mechanisms governing growth performance during heat stress in goats. The primary objective of the study was to establish the influence of heat stress on the expression patterns of different growth related genes in Malabari goats. The study was conducted for a period of 45 days in 12 Malabari goats randomly allocated into two groups: MC (n = 6; Malabari control) and MHS (n = 6; Malabari heat stress). At the end of study period, all 12 animals were slaughtered and their liver tissues were collected for gene expression and histopathological studies. The temperature-humidity-index (THI) inside the shed (74.9) proved that the animals were not stressed while in the outside environment (86.5) the animals were extremely distressed. The hepatic growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor-1 (IGF-1), leptin (LEP) and leptin receptor (LEPR) gene expression patterns were significantly (P < 0.05) lower in heat stress group as compared to the control group animals. In addition, negative correlation (P < 0.05) was also established between THI and all the growth related gene expression in the study. The hepatic histopathological section showed more fatty and degenerative changes (P < 0.05) in hepatocytes in MHS group as compared to MC group. The study offers the first thorough insight into the expression patterns of different growth related genes during heat stress exposure in goats. Further, the study established GH, GHR, IGF-1, LEP, LEPR genes to be the ideal markers to reflect growth potential in Malabari goats.

Resilience of three indigenous goat breeds to heat stress based on phenotypic traits and PBMC HSP70 expression.

The objective of this experiment was to evaluate the influence of summer heat stress on physiological and behavioral responses of Osmanabadi, Salem Black, and Malabari goats. The study also evaluated the differences in heat shock protein 70 (HSP70) expression pattern between these breeds. The study was conducted over 45 days during summer (April-May) using 36 1-year-old female goats by randomly allocating them into six groups with six animals in each group: Osmanabadi control (Osmanabadi CON), Osmanabadi heat stress (Osmanabadi HS), Malabari control (Malabari CON), Malabari heat stress (Malabari HS), Salem Black control (Salem Black CON), and Salem Black heat stress (Salem Black HS). The Osmanabadi CON, Malabari CON, and Salem Black CON animals were housed in a shed while the Osmanabadi HS, Malabari HS, and Salem Black HS groups were subjected to heat stress by exposing them to outside environment between 1000 and 1600 h during the experimental period. All 36 animals were provided with ad libitum feed and water. The data generated were analyzed by general linear model (GLM) repeated measurement analysis of variance. Results indicated that the drinking frequency (DF) was higher (p < 0.01) in heat stress groups (12.58, 12.25, and 10.75 times for the Osmanabadi HS, Malabari HS, and Salem Black HS, respectively) as compared to their respective control groups (5.67, 6.25, 5.58 times for the Osmanabadi CON, Malabari CON, and Salem Black CON, respectively). Water intake (WI) also showed similar trend to DF. The urinating frequency also (UF) differed between breeds with lower value (p < 0.05) recorded in the Salem Black HS (1.5 times) compared to the Malabari HS (2.92 times). The highest (p < 0.05) rumination time (RuT) was recorded in the Malabari HS (48.00 min) than both the Osmanabadi HS (20.91 min) and Salem Black HS (23.67 min). The heat stress increased (p < 0.05) all physiological variables at 1400 h. The findings of this study suggest RR, RT, and PBMC HSP70 are reliable biological markers for evaluating thermo-tolerance capacity of indigenous goat breeds.

Review: Adaptation of animals to heat stress.

Livestock plays an important role in the global economy. Climate change effects are not only limited to crop production, but also affect livestock production, for example reduced milk yields and milk quality, reduced meat production and reduced fertility. Therefore, livestock-based food security is threatened in many parts of the world. Furthermore, multiple stressors are a common phenomenon in many environments, and are likely to increase due to climate change. Among these stresses, heat stress appears to be the major factor which negatively influences livestock production. Hence, it is critical to identify agro-ecological zone-specific climate resilient thermo-tolerant animals to sustain livestock production. Livestock responds to the changing environments by altering their phenotypic and physiological characters. Therefore, survivability of the animal often depends on its ability to cope with or adapt to the existing conditions. So to sustain livestock production in an environment challenged by climate change, the animals must be genetically suitable and have the ability to survive in diversified environments. Biological markers or biomarkers indicate the biological states or alterations in expression pattern of genes or state of protein that serve as a reference point in breeding for the genetic improvement of livestock. Conventionally, identification of animals with superior genetic traits that were economically beneficial was the fundamental reason for identifying biomarkers in animals. Furthermore, compared with the behavioural, morphological or physiological responses in animals, the genetic markers are important because of the possibility of finding a solution to animal adaptability to climate change.