Adverse Effects Of Heat Stress Research Articles

Agronomic and genetic approaches for enhancing tolerance to heat stress in rice: a review

Rice is an important cereal crop worldwide that serves as a dietary component for half of the world’s population. Climate change, especially global warming is a rising threat to crop production and food security. Therefore, enhancing rice growth and yield is a crucial challenge in stress-prone environments. Frequent episodes of heat stress threaten rice production all over the world. Breeders and agronomists undertake several techniques to ameliorate the adverse effects of heat stress to safeguard global rice production. The selection of suitable sowing time application of plant hormones, osmoprotectants and utilization of appropriate fertilizers and signaling molecules are essential agronomic practices to mitigate the adverse effects of heat stress on rice. Likewise, developing genotypes with improved morphological, biochemical, and genetic attributes is feasible and practical way to respond to this challenge. The creation of more genetic recombinants and the identification of traits responsible for heat tolerance could allow the selection of early-flowering cultivars with resistance to heat stress. This review details the integration of several agronomic, conventional breeding, and molecular approaches like hybridization, pure line selection, master-assisted-selection (MAS), transgenic breeding and CRRISPR/Cas9 that promise rapid and efficient development and selection of heat-tolerant rice genotypes. Such information’s could be used to determine the future research directions for rice breeders and other researchers working to improve the heat tolerance in rice.

The Effects of Heat Shock Protein 70 Addition in the Culture Medium on the Development and Quality of In Vitro Produced Heat Shocked Bovine Embryos.

Simple SummaryEuropean dairy cows are extremely sensitive to heat stress. During hot summers milk yield is suppressed, welfare status of the cows is aggravated, and their fertility is seriously compromised. The observed subfertility is attributed to endocrinological alterations and mainly to inability of the early embryo to develop uneventfully until the implantation stages. To protect the integrity and the functionality of their cells, all mammals have inherent defense mechanisms against external insults. A major representative of these molecules are the heat shock proteins (HSPs) that are secreted by almost all cells. In this study, we examined the effects of exogenous HSP70 on the developmental competence and quality of early embryos produced in vitro, after 24-h exposure to slightly elevated temperature. Our findings imply that the temperature rise is detrimental for the developmental potential of the early embryos, and that the HSP70 can partly mitigate the harmful effects of heat stress, by improving the embryo yield and by reducing the adverse effects of heat stress on some embryo quality characteristics.The aims of the present study were to examine the effects of HSP70 addition in the in vitro culture medium of day 3 embryos on their developmental competence and quality. Bovine oocytes (n = 1442) were in vitro matured, inseminated and cultured for the first two days according to standardized methods. The presumptive zygotes were randomly allocated in three experimental groups: Control, C (embryos cultured at 39 °C throughout the culture period), group C41 (temperature was raised to 41 °C from the 48th to 72nd h post insemination (p.i.) and then it returned at 39 °C for the remaining culture period), and group H41 (the temperature modification was the same as in C41 and during heat exposure, HSP70 was added in the culture medium). Cleavage and embryo yield were assessed 48 h p.i. and on days 7, 8, 9, respectively and gene expression in day 7 blastocysts was assessed by RT-PCR. Blastocyst yield was the highest in group C39; and higher in group H41 compared to group C41. From the gene expression analyses, altered expression of 11 genes was detected among groups. The analysis of the orchestrated patterns of gene expression differed between groups. The results of this study confirm the devastating effects of heat stress on embryo development and provide evidence that HSP70 addition at the critical stages can partly counterbalance, without neutralizing, the negative effects of the heat insult on embryos, acting mainly through mechanisms related to energy deployment.

Influence of dietary genistein and polyunsaturated fatty acids on lipid peroxidation and fatty acid composition of meat in quail exposed to heat stress.

This experiment was conducted to investigate the effects of polyunsaturated fatty acids (PUFA) and genistein on performance and meat fatty acid profiles in quail exposed to heat stress. A total of 360 Japanese quail were divided into 12 groups in a 2 × 2 × 3 factorial design; each group comprised 30 quail with five replicates and were kept either at 22 ± 2°C for 24h/day (Thermoneutral, TN) or 34 ± 2°C for 8h/day (08:00 to 17:00h) followed by 22°C for 16h (heat stress, HS) conditions. The diet contained either two levels of PUFA at 15 or 45% of total fat or three levels of genistein at 0, 400, or 800mg/kg. Bodyweight gain, feed intake, and feed efficiency were lower (p ≥ 0.01) for quail reared under heat stress and fed low PUFA. Increasing dietary genistein in a linear manner improved the productive performance (p < 0.001). Heat stress caused increases in serum and thigh meat malondialdehyde (MDA) concentrations and decreases in genistein and vitamin E and A concentrations in serum and thigh meat (p < 0.001). High PUFA (PUFA45) in the diet of quail caused greater 18:2, 18:3 ALA, EPA, DHA, n-6, and n-3 PUFA as well as total PUFA and total USFA percentages (p < 0.001) in the thigh muscle, some of which decreased with heat stress (p ≥ 0.006) with no regard to genistein supplementation. This study revealed that genistein with greater doses along with greater PUFA inclusion to the diet of quail reared under heat stress is recommended for alleviating adverse effects of heat stress and for yielding healthier meat for human consumption.

Summer season induced heat stress associated changes on meat production and quality characteristics, myostatin and HSP70 gene expression patterns in indigenous goat

The study was conducted to assess the effect of heat stress on the meat production and quality variables in indigenous Malabari breed goats. 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). The MC group animals were housed inside the shed without exposure to outside environment while the MHS group animals were exposed to summer heat stress by keeping them outside the shed from 10:00 h to 16:00 h. At the end of the study, animals were slaughtered and their meat characteristics were assessed. The findings from the study revealed that heat stress caused significant reduction in live weight (P < 0.05), pre-slaughter weight (P < 0.01), hot carcass weight (P < 0.05), loin eye area (LEA) (P < 0.01), and fat score (P < 0.01). Fore saddle is the only primal cut which was significantly (P < 0.05) lower in weight in MHS as compared to MC group. Further, meat quality variables such as ultimate meat pH, water holding capacity (WHC) and shear force significantly (P < 0.01) increased during heat stress. Among the sensory characteristics, appearance (P < 0.01) and flavour (P < 0.05) reduced significantly in MHS group. However, plasma leptin level was significantly (P < 0.01) higher in MHS group. In addition, the skeletal muscle myostatin gene expression pattern was significantly (P < 0.05) lower while HSP70 gene expression was significantly (P < 0.05) higher in MHS as compared to MC group. Thus, it may be concluded from the study that indigenous Malabari goats possessed the inherent ability to maintain meat production by overcoming the adverse effects of heat stress. However, the severity of heat stress was reflected on the meat quality variables in this breed.

Seed Priming with Sulfhydral Thiourea Enhances the Performance of Camelina sativa L. under Heat Stress Conditions

Temperature is a key factor influencing plant growth and productivity; however, temperature fluctuations can cause detrimental effects on crop growth. This study aimed to assess the effect of seed priming on Camelina sativa L. under heat stress. Experimental treatments were comprised of; seed priming including, no-priming, hydropriming (distilled water priming), and osmopriming (thiourea applications at 500 ppm), heat stress (control = 20 °C and heat stress = 32 °C), and camelina varieties (7126 and 8046). Heat stress hammered crop growth as relative water content and photosynthetic rate were reduced by 35.9% and 49.05% in 7126, respectively, and 25.6% and 41.2% in 8046 as compared with control-no thiourea applied. However, osmopriming with thiourea improved the root and shoot length, and biomass production compared to control–no application under heat stress, with more improvement in variety 8046 as compared with 7126. Moreover, the maximum values of gas exchange and water relations were recorded at thiourea priming and no stress as compared with no-priming under heat stress that helped to improve seed yield by 12% in 7126 and 15% in 8046, respectively. Among the varieties, camelina variety 8046 showed better performance than 7126 by producing higher seed yield especially when subjected to thiourea priming. In conclusion, thiourea seed priming helped the plants to mitigate the adverse effects of heat stress by upregulating plant physiological attributes that lead to maintain camelina seed yield.

Nutritional management of dairy animals for sustained production under heat stress scenario

Dairy industry plays a significant role in the agriculture sector for sustainable growth. Heat stress, on the other hand, has been proven to have a detrimental impact on dairy output in terms of growth, reproductive performance and milk production in dairy animals, especially in tropical areas. Heat stress is one of the most significant issues facing the dairy industry, as rising temperatures and humidity limit animal productivity throughout the summer, resulting in devastating economic repercussions. The purpose of this review is to gather knowledge on the effects of heat stress on dairy output and how to ameliorate them. The diversion of energy resources from the production to the adaptation pathway may be responsible for the loss in productive capacity of dairy animals, when they are exposed to heat stress. There are different approaches pertaining to relieving the adverse effects of heat stress on dairy production system. These approaches may be classified into three major categories viz. genetic, management and nutritional interventions. These approaches might help dairy animals to perform better by reducing the harmful impacts of heat stress. Appropriate shelter design, giving shade, employing sprinklers, installing cooling devices, and using fans and ventilation systems are among the management strategies. The nutritional interventions comprise ration balancing and providing essential micronutrients to improve the productive and reproductive performance. Some of the most widely used dietary measures to ensure optimal production are inclusion of protein or fat (prill fat), micronutrients antioxidants (vitamins and minerals) and some feed additives (Astaxanthin, betaine, melatonin, Chlorophytum borivilianum) in the diet. These antioxidants and feed additives can be used to attenuate the negative effects of environmental stress. Furthermore, providing adequate energy and antioxidants help to ensure optimum growth, milk production and reproduction efficiency during heat stress. This review provides an overview of the consequences of heat stress on dairy animals, emphasizes essential nutritional strategies for heat stress reduction in dairy animals, and evaluates the influence of various feed supplements on growth, productivity and physiology.

Thiourea application improves heat tolerance in camelina (Camelina sativa L. Crantz) by modulating gas exchange, antioxidant defense and osmoprotection

Heat stress can have devastating effects on agricultural production and crop productivity. This study was conducted to evaluate the effect of exogenously applied thiourea on heat stress tolerance through osmotic adjustment in camelina (Camelina sativa L.). The study comprised of three factors: i) Heat stress; HS0 = 25 °C (control) and HS1 = 35 °C (stress), ii) camelina genotypes; G1 = 611 and G2 = 618, and iii) thiourea; TU0=control-no thiourea supplementation, TU1=thiourea supplementation (1000 mg/L) at vegetative stage (BBCH (Biologische Bundesanstalt Bundessortenamt and Chemical Industry) two codes scale-31), and TU2=reproductive stage (BBCH two codes scale-59). Heat stress caused a reduction in the growth, carbon assimilation, and chlorophyll contents with more so where no thiourea was applied. Heat stress also caused a significant increase in lipid peroxidation (measured by leaf malondialdehyde contents), hydrogen peroxide, and electrolyte leakage in plants not receiving thiourea application. In addition, dry matter per plant, photosynthetic rate, and seed yield was reduced by 32.7, 40.8, and 60.9 %, respectively under elevated temperature as compared with control-no stress. However, the foliage applied thiourea alleviated the adverse effects of heat stress in camelina applied either at vegetative or reproductive growth stage by protecting the photosynthetic pigments (chlorophyll a, b) which helped to maintain photosynthetic efficiency by (14 %) than no thiourea applications). Foliar-applied thiourea also reduced oxidative damage by upregulating the antioxidants such as catalase, protease, and ascorbate peroxidase, and by improving osmolytes i.e., total soluble sugars, total soluble proteins, proline, and glycine betaine. Seed yield was improved by 57.8 % due to thiourea supplementation under heat stress compared with no thiourea application. Among the stages, thiourea application at the reproductive stage was more effective than the vegetative. Genotype 618 has produced highest dry weight per plant, photosynthetic efficiency, antioxidant activity under heat stress relative to genotype 611. In conclusion, thiourea application (1000 mg/L) improved heat tolerance in camelina by modulating gas exchange, antioxidant defense, and osmoprotectant. Thiourea application at the reproductive stage was more effective than the vegetative stage and 618 was heat stress tolerant genotype compared with genotype 611 which was relatively sensitive to heat stress.

بررسی مقایسه ای فلفل قرمز با محرکهای رشد تجاری بر عملکرد جوجههای گوشتی در شرایط تنش گرمایی

Effect of red pepper in comparison to commercial growth promoters, Biostrong and Oleobiotec, on growth performance, nutrient digestibility, and other traits of broilers under heat stress conditions using 200 day-old broiler chickens mixed male and female of ArborAcers strain in a completely randomized design with four treatments, five replications and ten chickens per replicate were evaluated. Treatments included a basal diet without additives and a basal diet containing 10, 0.1, 0.15 g/kg red pepper, Biostrong, and Oleobiotec,respectively. At the beginning of third week, the birds were exposed to heat stress for six hours per day. During the 42 days of the experiment, the mean minimum and maximum temperatures were 25°C and 33°C. Feed intake, weight gain, feed conversion ratio, the weight of internal organs, caecal microflora, and precaecal nutrient digestibility were measured for the heat stress period. The use of red pepperimproved the feed conversion ratio and daily weight gain in grower and finisher periods and increased protein, lipid, and dry matter precaecal digestibility, the relative weight of bursa of Fabricius, spleen, and gizzard, and decreased the Ecoli population in caecum compared to the control treatment (P≤0.05). Biostrong and Oleobiotec did not affect growth performance, prececal nutrient digestibility, and the E.colipopulation. Overall, using the red pepper in the diet of broilers compared to commercial growth promoters reduced the adverse effects of heat stress on growth performance, nutrient digestibility, and caecal microflora.

Organic Diallyl-n-Sulfide (Dn-S) inhibited the glycogenolysis pathway and heart failure of heat-stressed laying hens

Heat stress causes a decrease in metabolic and immune function, thus resulting in decreased production. Natural extracts such as the active compound diallyl-n-sulfide (Dn-S) are one strategy to overcome the adverse effects of heat stress. One hundred and fifty female laying hens, with a mean bodyweight of 1191.38±25.54 g, aged 11 weeks, were used in this experiment to study Dn-S’s impact from garlic on the metabolite profile of the glycogenolysis pathway and heart failure in laying hens. The sample of laying hens was divided into five treatment groups, each with 25 samples and the Dn-S from garlic isolated by distillation technique. The study was carried out with three types of experimental treatment, groups with a zone temperature of heat stress (38°C) and without Dn-S, heat stress (38°C) and 100 μL Dn-S/sample, heat stress (38°C) and 1125 μL Dn-S/sample, respectively. Based on the results of the study, it shows that heat stress causes an increase in the rate of glycogenolysis. It appears that the administration of 200 μL Dn-S effectively reduces the rate of glycogenolysis and can maintain a normal heart condition. It was concluded that heat stress in laying hens could be avoided by administering diallyl n-sulfide (Dn-S) from garlic. Dn-S has an essential role in preventing changes in the osmotic pressure of body fluids. Overall, it can cope with the metabolic and physiological changes associated with heat stress.

Do nitrogen and zinc application alleviate the adverse effect of heat stress on wheat (Triticum aestivum L.)?

Late-season heat stress (LSH) is a limiting factor for wheat production. Besides, low zinc and poor protein diet usually is a problem in low-income countries. The primary calorie source in such countries is prepared from bread. This study aims to mitigate heat stress by zinc and nitrogen application and improve zinc and protein content in wheat grain. We did the field experiments as a split-split-plot based on a randomized complete block design with four replications to assess zinc and nitrogen’s possible mitigation effect on LSH and protein and zinc enrichment of wheat grain during two years. Factors included LSH by delay in planting date (optimum, late, and very late) as the main plot, nitrogen (0, 75, 150, and 225 kg ha–1) in subplots, and zinc (0, 10, and 20 kg ha–1) as sub-subplots. We measured yield, yield components, physiological traits, zinc, and protein contents in the grain. Results showed that the highest relative water content and cell-membrane thermal stability were attained at the optimum planting date, 150 kg N ha–1 and 20 kg Zn ha–1. The maximum chlorophyll a and carotenoids contents in wheat cells were recorded in the optimum planting date, 225 kg N ha–1, and 20 kg Zn ha–1. Heat stress reduced the grain yield. In the second year of the experiment, the grain number per unit area was more than that of the first year; however, the highest grain yield was achieved in the first year owing to the higher mean grain weight. Nitrogen application decreased the adverse effects of heat stress on grain yield by increasing the grain number. Zinc application diminished the adverse effects of heat stress by increasing the mean grain weight. The adverse impact of the LSH on grain yield was more than that of biological yield. Heat stress reduced the hectolitre weight and zinc content of the grain. Meanwhile, it increased grain protein. In general, under LSH, the application of 225 kg N ha–1 and 20 kg Zn ha–1 can reduce the adverse effects of heat on the grain quality and quantity.

Zinc alleviates the heat stress of primary cultured hepatocytes of broiler embryos via enhancing the antioxidant ability and attenuating the heat shock responses.

Zinc (Zn) has been shown to attenuate the adverse effects of heat stress on broilers, but the mechanisms involving this process remain unclear. We aimed to investigate possible protective mechanisms of Zn on primary cultured hepatocytes of broiler embryos subjected to heat stress. Three experiments were conducted. In Exp. 1, hepatocytes were treated with 0, 50, 100, 200, or 400 μmol/L added Zn as inorganic Zn sulfate (iZn) for 12, 24 or 48 h. In Exp. 2, cells were exposed to 40 °C (a normal temperature [NT]) and 44 °C (a high temperature [HT]) for 1, 2, 4, 6, or 8 h. In Exp. 3, cells were preincubated with 0 or 50 μmol/L Zn as iZn or organic Zn lysine chelate (oZn) for 8 h under NT, and then incubated with the same Zn treatments under NT or HT for 4 or 6 h. The biomarkers of antioxidative status and heat stress in cells were measured. The results in Exp. 1 indicated that 50 μmol/L Zn and 12 h incubation were the optimal conditions for increasing antioxidant ability of hepatocytes. In Exp. 2, the 4 or 6 h incubation under HT was effective in inducing heat shock responses of hepatocytes. In Exp. 3, HT elevated (P < 0.01) malondialdehyde content and expressions of heat shock protein 70 (HSP70) mRNA and protein, as well as HSP90 mRNA. However, Zn supplementation increased (P < 0.05) copper zinc superoxide dismutase (CuZnSOD) activity and metallothionein mRNA expression, and effectively decreased (P < 0.05) the expressions of HSP70 mRNA and protein, as well as HSP90 mRNA. Furthermore, oZn was more effective (P < 0.05) than iZn in enhancing CuZnSOD activity of hepatocytes under HT. It was concluded that Zn (especially oZn) could alleviate heat stress of broiler hepatocytes via enhancing their antioxidant ability and attenuating heat shock responses.

Adverse Effects of Heat Stress on the Intestinal Integrity and Function of Pigs and the Mitigation Capacity of Dietary Antioxidants: A Review.

Simple SummaryHeat stress is a significant threat to the pigs’ production performance as it greatly affects various body systems, particularly those that are responsible for nutrient digestion and absorption. Heat-stress-induced stressors such as oxidative stress threaten the integrity and functionality of the intestine by negatively affecting its morphology and histology through reduction of villus height, crypt depth, villus height to crypt depth ratio, mucosal surface and villi sloughing. Its protective function is also compromised as heat stress negatively influences the expression of tight junction proteins and disrupts the tight junction barrier function, leading to endotoxemia. These adverse effects of heat stress can be highly mitigated by supplementing dietary antioxidants, as these substances positively influence the intestinal integrity and function of pigs through the improvement of intestinal morphology and histology. Reduction of blood endotoxin through improved tight junction barrier function and depletion of oxidative stress with enhanced mucosal antioxidant capacity is also evident upon such supplementation.Heat stress (HS) significantly affects the performance of pigs by its induced stressors such as inflammation, hypoxia and oxidative stress (OS), which mightily strain the intestinal integrity and function of pigs. As heat stress progresses, several mechanisms in the intestinal epithelium involved in the absorption of nutrients and its protective functions are altered. Changes in these mechanisms are mainly driven by cellular oxidative stress, which promotes disruption of intestinal homeostasis, leading to intestinal permeability, emphasizing intestinal histology and morphology with little possibility of recovering even after exposure to HS. Identification and understanding of these altered mechanisms are crucial for providing appropriate intervention strategies. Therefore, it is this papers’ objective to review the important components for intestinal integrity that are negatively affected by HS and its induced stressors. With due consideration to the amelioration of such effects through nutritional intervention, this work will also look into the capability of dietary antioxidants in mitigating such adverse effects and maintaining the intestine’s integrity and function upon the pigs’ exposure to high environmental temperature.

Analysis of long non-coding RNAs in skeletal muscle of Bama Xiang pigs in response to heat stress.

The aim of this study was to identify differentially expressed long non-coding RNAs (lncRNAs) molecules and predict their target genes related to muscle development and lipid metabolism in longissimus dorsi (LD) muscles of Bama Xiang pigs under constant heat stress. Ten male Bama Xiang pigs with an average initial body weight of 14 kg were randomly divided into control group (22°C) and heat stress (35 °C) group. The experiment lasted for 28 days. All the pigs were slaughtered at the end of the experiment, and LD muscles were collected for muscle quality analysis and transcriptome sequencing. Heat stress reduced meat quality of Bama Xiang pigs. lncRNAs in LD were identified systematically by deep RNA sequencing between the two groups. The results showed that 365 lncRNAs from the LD were identified, including 128 intergenic lncRNAs, 82 intronic lncRNAs, and 155 anti-sense lncRNAs. The differences lie in transcript of length, number of exons and wider size distribution, and expression level per KB fragment in three subtypes of lncRNAs. The three types of transposable elements coverage, including Line/L1, SINE/tRNA, and LTR/ERVL-MaLR, are the highest in mRNA and the three subtypes of lncRNAs in pigs. lncRNAs and mRNAs were different in comparison of features. The results predicted the target genes of the significant differentially expressed lncRNAs related to muscle development and lipid metabolism. This is the first study to expand the knowledge about muscle-related lncRNAs biology in Bama Xiang pigs under heat stress and will contribute to the development of alleviating the adverse effects of heat stress on pork quality targeting lncRNAs.

Thermal stress and high stocking densities in poultry farms: Potential effects and mitigation strategies.

Environmental changes pose significant threats to agricultural activities particularly animal production. These changes have induced major concerns which will negatively affect the poultry health and productivity under the current climate changes. Moreover, they also alter the immunological status of the exposed birds and make them susceptible to different diseases. The adverse effects of environmental stress also include poor performance of birds (reduced feed intake, growth, feed efficiency, immunity, and egg production) and inferior product quality. The adverse effect of heat stress on different quail breeds like Japanese quail, bobwhite quail, scaled quail, and Gambel's quail ranged from decreased growth rates (11.0-14.5%), body weight (7.7-13.2%), feed intake (6.1-21.6%), feed efficiency (4.3-8.6%), and egg production (6.6-23.3%). Also, birds reared under heat stress (34°C) had significantly decreased Haugh units by 10.8% and egg weight by 14.3% in comparison with the control group (reared at 22°C). On the other hand, increasing stoking density from 30 to 45kg/m2 also negatively affected the feed intake and body weight. Recent studies have focused on evaluating the potential adverse effects of different environmental stresses on poultry performance, behavior, welfare, and reproduction. It is imperative to understand better the interaction of different environmental factors and their subsequent effects on avian physiology, to spotlights on the effective management and nutritional strategies to alleviate the adverse effects of different stresses in poultry. This review aims to present a comprehensive overview of physiological manifestations of major environmental stresses including thermal stress (heat and cold stress) and high stocking densities on poultry health and production. Moreover, we have also critically evaluated the scope and efficacy of some potential strategies to mitigate the influences of these environmental stressors in different poultry species.

Rice seedlings showed a higher heat tolerance through the foliar application of biostimulants

The use of biostimulants is an agronomic tool to improve plant tolerance to abiotic stress in plants. This study explored the effect of foliar biostimulants sprays such as brassinosteroids (BR), amino acids (AA), nitrophenolates (NP) or a biostimulant based on botanical extracts (BE) on leaf gas exchange parameters [photosynthesis (PN), stomatal conductance (gs) and transpiration (E)], leaf photosynthetic pigments, lipid peroxidation of membranes and proline content of two commercial rice genotypes [‘Fedearroz 67’ and ‘Fedearroz 60’] under heat stress conditions. The established treatments were: i) plants without heat stress and foliar applications of biostimulants (C), ii) plants under heat stress and without foliar applications of biostimulants (HT), and iii) plants with heat stress and three foliar applications with BR (1 mL·L-1), AA (30 mL·L-1), NP (15 mL·L-1) or BE (15 mL·L-1). The results showed that the application of BR, AA, NP or BE increased the values ​​of PN (~14.5 µmol CO2·m-2·s-1), gs (~0.46 mmol·m-2·s-1) and E (~43.9 H20 day-1·plant-1) compared to plants (both genotypes) not treated with biostimulants under heat stress (9.9 µmol CO2·m-2·s-1 for PN, 0.31 mmol·m-2·s-1 for gs, and 27.3 H20 day-1·plant-1 for E). Foliar biostimulant sprays also caused a lower malondialdehyde and proline production in rice genotypes under heat stress. In conclusion, the biostimulants BR, AA, NP, or BE can be considered an agronomic strategy to help mitigate the adverse effects of heat stress in rice areas where periods of high temperatures are expected during the day in Colombia.

EFFECT OF SUPPLEMENTED SOME ANTIOXIDANTS TO BROILER DIETS ON GROWTH PERFORMANCE, IMMUNE RESPONSE AND ANTIOXIDANT STATUS DURING SUMMER SEASON

The current experiment aimed to estimate some antioxidants ability mainly, selenium, vitamins B6 and C to overcome adverse effect of heat stress during summer months. Total of 360 one- day-old broiler chicks were randomly divided into 9 treatments with four replicates (10 chicks/each). The experiment period extended from 1 day to 40 days of age where ambient temperature ranged from 36 to 41°C and relative humidity ranged from 30 to 55%. The 1st group fed basal diet that satisfied strain requirement as control treatment. The 2nd group fed control basal diet supplemented with vitamin E (50 mg/kg diet) and acted as control plus to estimate efficiency of antioxidants. Experimental treatments from the 3rd to the 9th fed basal diet supplemented with 3 mg vitamin B6, 200mg vitamin C, 0.10 mg Se, 3 mg vitamin B6+ 200mg vitamin C, 3 mg vitamin B6 + 0.10 mg Se, 200 mg vitamin C + 0.10 mg Se, or 3 mg vitamin B6 +200mg vitamin C+ 0.10 mg Se respectively.. Parameters of growth performance, carcass characteristics, some plasma constituents, immunity and antioxidant status were investigated. Malondialdehyde was estimated in frozen (6 months at -20 °C) thigh muscles to determine antioxidant status. The results appeared significant improvement of growth performance and malondialdehyde were reduced in plasma and thigh muscles. Dressing, abdominal fat and giblets percentages did not affect. While, significant improvement was observed in some hematological parameters, cellular immunity and antioxidant status. In contrast antibodies titer against Newcastle Disease Virus and Avian flow Virus (H5N1) did not affect. Briefly, the overall experimental results showed that supplementing broiler diets with selenium combined with vitamin B6, vitamin C or both were more effective to improve growth performance, broiler meat quality, immunological and antioxidant status for broiler chicks reared during hot summer months.

Antioxidant Statues, Growth and Some Physiological Performances of the Gimmizah Male Chickens Supplemented by Dietary Spirulina Platensis under Chronic Heat Stress.

The present study was carried out to study the effect of Spirulina supplementation on the growth and some physiological performances of the Gimmizah males exposed to heat stress (HS). A total number of 150 male 4 weeks old Gimmizah were randomly allocated in five groups (3 replicates, 10 chicks each). The first (positive control, PC) was reared under 22-24OC and PH 45-55% and fed unsupplied basal diet, B). Whereas, the other groups were reused under HS (38°C±1; 55-65 % RH) for three successive days /wk from 11.00 a.m until 15.00 p.m, through the experimental period (4 to 14 wks of age) in a battery brooders. The first HS group was used as a negative control (NC) and fed B. The 3rd and 4rd groups fed B plus 250 and 150 mg Spirulina /kg diet, respectively. The 5 group was fed the B plus 75 mg VE /kg diet. The feed consumption was significantly decreased for all groups under HS compared with PC group, while FCR for the groups under HS (supplied with Spirulina or VE) were significantly improved compared with NC. The differential of leukocytic count for the NC group recorded the significant increase on Lymphocyte, Heterophil and the ratio of H/L compared with other groups. The concentration of globulin and activity of GSH-PX were significantly improved for the groups supplied with both levels of Spirolina under HS compared with the NC group. The highest Infections Bronchitis titer was recorded for the group supplied with VE and PC group. In conclusion, addition of 150 and 250 mg Spirulina platensis /kg diet improved performance, immunity and can be decreased the adverse effect of heat stress for Gimmizah mail during growing period (4-14 wks of age).

Impact of in ovo Injection of Certain Vitamins to Improve the Physiological Conditions of Hatching Chicks

Exposure of breeder hens to hyperthermia causes disturbances in the breeder's eggs due to insufficient nutrient deposition from heat-stressed hen into the egg. Therefore, this experiment was conducted to test the hypothesis that the adverse effects of heat stress on hatchability, embryonic growth and hatchling health status could be ameliorated by in ovo injection of certain vitamins. A total of 270 fertile eggs from Fayoumi breeders (45 weeks) were randomly assigned to 6 groups (45 eggs/group). During the egg collection period in the summer season, birds were maintained at 9-13°C above the standard thermo-neutral temperature. The experimental groups were: negative control (eggs not injected either with vitamins or Sterile Deionized Water (SDW)), positive control (eggs injected with 0.1 mL of SDW/egg) and four other treatments in which vitamins A, E, D3 and folic acid were injected (1 mg of each vitamin dissolved in 0.1 mL of SDW/egg). The eggs were incubated at 37.7°C and 65% relative humidity in an automatic incubator. The residual yolk, embryo length and weight and hatchability% were improved (p<0.01) in all vitamins in ovo injected groups compared with both controls. Hatchling weight and the assessed health status indices were increased (p<0.01) in all vitamins in ovo injected groups compared with both controls. It is concluded that direct injection of vitamins into eggs laid by heat-stressed breeders is an effective way of reducing the disturbance in eggs resulting from inadequate nutrient deposition from hen to egg.

SEASONAL EFFECTS ON OESTRUS PATTERNS AND PROGESTERONE PROFILES OF YANKASA EWES OF DIFFERENT AGE-GROUPS IN THE SUB-HUMID TROPICS

Oestrus patterns and serum progesterone profiles of 10 adult and 10 yearling Yankasa ewes were investigated in the late hot-dry and late-wet seasons in the subhumid tropical climate of Zaria, Nigeria. The proportions of ewes which came on heat once, twice or thrice within the experimental periods in the late hot-dry and late-wet seasons were 25, 15 and 0%, and 5, 10 and 85% respectively, while mean oestrous cycle length was significantly longer (P&lt;0.001) in the hot-dry season than in the late-wet season (30.9 vs 18.4 days) due to the higher incidence of anoestrus in the former. However, the mean duration of oestrus was not affected by season. Mean serum progesterone levels were significantly (P&lt;0.05) higher in the late-wet season than in the late hot-dry season (1.57 vs 0.52 ng/ml). However, there was a highly significant (P&lt;0.001) interaction between season and age group in mean serum progesterone levels due to a relatively greater depression in progesterone levels in yearling ewes during the hot-dry season compared with adult ewes. The observed disruptions in the oestrus cycle and serum progesterone levels of the ewes in the hot-dry season confirm the adverse effect of heat stress on the reproductive behaviour of ewes.

Impacts of Probiotic feeding on Behavior and Welfare related parameters of Heat Stressed Broilers

This study was performed to detect the efficacy of probiotic (PROBAC plus) as anti-stress on behavior and welfare of heat-stressed broilers (32-35oc) from age 22d to 42d. One-hundred twenty chick were divided into 4 groups. The first group was control (basal diet), second was broilers reared at high temperature (basal diet), third was broilers reared at high temperature (basal diet + Probiotic) and fourth was probiotic group (basal diet + probiotic). Behavioral patterns of broilers were recorded from week 4 till the end of the experiment. At last day of experiment, 10 birds from each group were slaughtered to collect blood samples. Blood films were stained for measuring heterophils / lymphocytes (H / L) ratio. Serum cortisol was measured. The results showed that feeding, comfort behaviors, and movement activities of heat-stressed broilers were decreased while the drinking frequency was increased. Heat-stressed birds showed higher H / L ratio and cortisol concentration. Addition of probiotic either to diets of birds reared with or without stress improved some behaviors of birds and decreased H / L ratio and cortisol hormone. These results suggest that feeding of probiotic can be a useful tool to counteract the adverse effects of heat stress in broiler industry.