Anatomy & Physiology: Current Research
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Hen-Day Egg Production and Qualitative Egg Indices in Laying Hens Administered with Lycopene and Vitamin E during the Hot-Dry Season

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Introduction

Oxidative stress is a critical factor implicated in the initiation, development and progression of most ovarian dysfunctions, which may be exacerbated during the inclement hot-dry season. In poultry production, various environmentally-induced stresses, ranging from poor nutrition [1-6], social stress [6], and heat stress [7,8], exert remarkable depressive effects on poultry well-being and optimum productivity [8]. Heat stress results from outrages in environmental temperature, often associated with the zone during the hot-dry season. The severity of environmental temperature is aggravated by concurrent increase in relative humidity, which impairs performance and induces oxidative stress in poultry. In the tropical environment, heat stress constitutes a major debilitating factor to poultry production [9,10]. It results from a negative balance between the net amount of energy flowing from the laying hen’s body to its surrounding environment and the amount of heat energy produced by the hen. This imbalance may be caused by salient environmental factors, including sunlight, thermal irradiation, air temperature, relative humidity, air movements, metabolic rate, and impaired thermoregulatory mechanism [7,8,11]. Lycopene is the predominant carotenoid in tomatoes and one of the major carotenoids in the serum and tissues [12,13]. When lycopene is incorporated in avian tissues, especially in egg yolk, it exhibits significant antioxidant activity [14]. Lycopene quenches Reactive Oxygen Species (ROS), including singlet oxygen and other oxidising species and, thus, protects the cells from oxidative damage, occurring in heat stress [2,15,16]. Vitamin E is an essential fat-soluble nutrient, often called tocopherol. Alpha-tocopherol is essentially the most predominant, having the highest biological activity in many species. It is a potent antioxidant involved in the prevention and management of infertility and other reproductive anomalies [17,18]. Domestic birds do not synthesize enough vitamin E and, consequently, they are dependent on dietary sources to meet the body requirements [3,19,20]. Therefore, vitamin E supplementation in poultry nutrition, through better protection against oxidative stress [3,21], improves fertility, hatchability and the qualitative post-hatch performance of avian chicks [18,22].

The aim of the study was to evaluate the effects of lycopene and vitamin E on hen-day egg production and qualitative egg indices in laying hens during the hot-dry season.

Materials and Methods

Location of the study

The experiment was performed in a standard poultry farm in Zaria, located at latitude 11°N, 12/N and longitude 7 °E, 8/E, elevation of 650 m above sea level, and in the Northern Guinea Savannah zone of Nigeria. The zone has annual mean maximum and minimum temperatures of 31.8 ± 3.2°C and 18.0 ± 3.7°C, respectively. It is characterised by three seasons: Harmattan (colddry) occurring in November–February, rainy (June–October) and hot-dry seasons (March–May) [11,23]. The hot-dry season has been described as the most stressful to laying hens [24,25].

Thermal environmental data

A dry- and wet-bulb thermometer (Mason’s Type Wet-and Dry-bulb hygrometer (GH Zeal Limited, London, England), positioned at the height of 2 m from the floor in the experimental poultry pen was used to record the dry- and wet-bulb temperatures daily every three hours, beginning from 06:00 h to 18:00 h, throughout the duration of the study that lasted for five weeks. The Temperature-Humidity Index (THI), used to determine the heat load in the laying hens, was calculated from the dry- and wet-bulb temperatures [26]:

THI=0.6 Tdb+0.4 Tdw

Where:

THI: Temperature-Humidity Index for the laying hen (°C)

Tdb: dry-bulb Temperature (°C)Twb: wet-bulb Temperature (°C)

Flock management

apparently, healthy ISA Brown laying hens, aged 41 weeks with a mean live weight of 1.8 ± 0.5 kg were used for the study. They were maintained in deep litter in an open-sided standard poultry pen unit. The hens were divided by simple randomisation into four groups, comprising 100 group-penned laying hens each and maintained on layer mash (Vital Feeds Ltd., Jos, Nigeria). The feed had nutritive values of 16.50% crude protein, 6.5% crude fibre and 2650.0 kCal/kg metabolisable energy. The flock was given access to feed and water ad libitum. Standard routine vaccinations and periodic prophylactic medications were administered to the hens. The husbandry and the conduct of the experiments on the laying hens were performed in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes (Council of Europe No 123, Strasbourg 1985). All the experimental protocols described were approved by the Ethics Review Committee for Animal Experimentation of Ahmadu Bello University, Zaria, Nigeria.

Experimental design

The study was conducted on four different groups of laying hens in a laying pen, comprising 100 birds per group. Each pen was identified according to its experimental role. The lycopenetreated group was administered orally with 30 mg lycopene⁄kg body weight per day [27], while the control group was given the equivalent of water only. The lycopene+ vitamin E-treated hens were administered orally with 30 mg lycopene, combined with 250 mg vitamin E⁄kg body weight per day, while the vitamin E-penned layers received vitamin E only at a dose of 250 mg⁄kg body weight per day [28]. All administrations were performed orally, using a gavage between 7:00 h and 8:00 h daily for five weeks. Feeds and water were available to the hens ad libitum.

The hen-day egg production and mean egg weight in each pen were recorded daily as indices of egg production. The weekly eggshell weight and eggshell diameter were evaluated throughout the study period as described by Mack et al. [29].

Data analyses

The data obtained were expressed as mean ± Standard Error of the Mean (mean ± SEM). Variations in hen-day egg production and eggshell qualitative indices of the laying hens were analysed using repeated-measures Analysis of Variance (ANOVA), followed by Tukey’s multiple comparison post-hoc test. Values of P<0.05 were considered significant. Data were analysed using GraphPad Prism, version 5.03 (GraphPad Software, San Diego, California, USA, www.graphpad.com).

Results

Thermal environmental conditions

The thermal environmental conditions of DBT and THI data are presented in Tables 1 and 2. Weekly mean DBT values were significantly (P<0.05) lower during the morning hours between 6:00 h and 9:00 h than the values obtained at 12:00, 15:00 and 18:00 h. The lowest DBT (24.3 ± 0.5°C) was recorded at 6:00 h during the fourth week of the study, while the highest value (36.7 ± 0.6°C) was obtained at 9:00 h in the 3rd week of the study (Table 1). The DBT varied significantly (P<0.05) between 9:00 h and 12:00 h; thereafter, the variations were not significantly (P>0.05) different.

Table 1: Weekly diurnal fluctuations in dry-bulb temperature (°C) during the hot-dry season.

Temperature-humidity index

The THI was lowest at 0:600 h (23.1 ± 0.05°C), obtained at the 4th week of the study; while the highest (P<0.05) value (33.3 ± 0.4°C) was recorded at the 3rd week. The overall THI value (28.42 ± 0.42°C) was recorded at 0:600 h, 09:00 h, 12:00 h, 15:00 h and 18:00 h, respectively. The overall pattern of THI decreased significantly (P<0.05) with time of the day in the order: 18:00>15:00 h>12:00 h>09:00 h>06:00 h (Table 2). During the study period, the laying hens panted frequently; most often from 10:00 h of the day, and the intensity increased remarkably between 12:00 h and 18:00 h. Panting recorded shortly after 9:00 h was heightened between 15:00 h and 18:00 h of the day due to sustained heat load. In some cases during the study, the laying hens were visibly going-off their feeders and concentrating activity around the drinkers, where they were observed to drink more intensively and rested under their feed augers. They also spent more time with their wings elevated, less time moving or walking, and more time resting.

Table 2: Temperature-humidity index (°C) in poultry pen during the hot-dry season.

Effect of lycopene and vitamin E on hen-day egg production

Supplemental administration of lycopene and vitamin E significantly (P<0.05) increased daily egg production, which resulted in a remarkable weekly egg output, when compared with the controls. Laying hens that received lycopene+ vitamin E had hen-day egg production, ranging from the lowest mean value (59.0 ± 1.2 %) to the highest hen-day (66.57 ± 1.2 %) during the 4th and 3rd week. The extreme minimum and extreme maximum values recorded in lycopene+ vitamin E laying hens were 56.0% and 72.0%, respectively. The overall mean value of hen-day egg production of 62.7 ± 1.0% was obtained in lycopene+ vitamin E laying hens (Table 3). In laying hens supplemented with vitamin E alone, weekly hen-day egg production ranged between 59.0 ± 1.9% and 65.3 ± 1.5% hen-day; and the overall mean hen-day (62.1 ± 1.2 %) was not significantly (P>0.05) different from that recorded in lycopene+ vitamin E laying hens (62.7 ± 1.0%). The overall mean hen-day for the control laying hens (56.0 ± 0.8 %) was the lowest (P<0.05), compared to the value recorded in any of the experimental groups (Table 3).

Table 3: Weekly hen-day egg production (%) in laying hens during the hot-dry season (n=100 per group).

Relationship (r) between temperature-humidity index and hen-day egg production

The relationship between THI and hen-day egg production was positive in most of the weeks of recordings, particularly in vitamin E group, followed by the lycopene group (Table 4).

Table 4: Correlation co-efficients between temperature-humidity index and hen-day egg production during the hot-dry season.

Effect of lycopene and vitamin E on eggshell diameter

The eggshell diameters (thickness) of the laying hens during the hot-dry season are presented in Table 5. Eggshell thickness was the lowest (P<0.05) in control laying hens, compared to all other groups. Overall, eggshell thickness was highest in lycopene+ vitamin E laying hens (0.28 ± 0.02 mm). The laying hens administered with vitamin E alone had the thickness of 0.22 ± 0.02 mm, which did not differ from that of control laying hens (0.18 ± 0.02 mm), but was significantly (P<0.05) lower than the values for the rest groups (Figure 1).

Table 5: Eggshell diameter (mm) in ISA Brown laying hens administered with lycopene and vitamin E during the hot-dry season (mean ± SEM; n=10 per group).

Figure 1: Overall mean eggshell diameter in ISA Brown laying hens during the hot-dry season a, b, c=Values with different superscript letters between layer groups are significantly (P<0.05) different. L+VE=lycopene + vitamin E-administered hens; L= lycopeneadministered hens; VE=vitamin E-administered hens; CONT=control hens.

Effect of lycopene and vitamin E on eggshell weight

The eggshell weight in lycopene and/or vitamin E laying hens did not differ significantly at week 1, compared to the controls. However at week 2, all the antioxidant-treated groups recorded higher eggshell weights, compared to the controls. At week 3, although lycopene+ vitamin E and lycopene hens had eggshell weights that were higher than those of controls, the values did not differ from that recorded in vitamin E laying hens. At week 4, lycopene+ vitamin E and vitamin E laying hens recorded eggshell weights that were higher than those of lycopene hens, particularly in the controls. At week 5, only the lycopene+ vitamin E group recorded higher eggshell weight compared to the controls.

The control laying hens recorded the least overall eggshell weight (6.7 ± 0.02 g); which was significantly (P<0.05) lower than the values recorded in lycopene+ vitamin E, lycopene and vitamin E lay- ing hens (7.3 ± 0.24 g, 7.3 ± 0.3 g and 7.2 ± 0.3 g, respectively) (Table 6 and Figure 2).

Figure 2: Overall mean eggshell weight in ISA Brown laying hens during the hot-dry season a, b, c=Values with different superscript letters between layer groups are significantly (P<0.05) different. L+VE=lycopene + vitamin E-administered hens; L= lycopeneadministered hens; VE=vitamin E-administered hens; CONT=control hens.

Table 6: Eggshell weight (g) of ISA Brown laying hens administered with lycopene and vitamin E during the hot-dry season (mean ± SEM; n=10 per group).

Discussion

The results show that during the hot-dry season, the afternoon and evening hours were most thermally stressful to the laying hens. The ambient temperatures and correspondingly the heat load rose progressively from daily nadirs (minimum) at early hours of the day, beginning from 06:00 h and attaining the peak (maximum) at the end of the day, at 18:00 h. Diurnal variations in DBT values show that the overriding environmental factor affecting the hens was the ambient temperature. The finding was similar to the reports of Vathana et al., [30-32] that ambient temperature is characterised by diurnal variations and it is the principal determinant of the metabolic parameters. The recorded trend in environmental temperature was similar to the finding of Dzenda et al., [11,23] that heat stress is prevalent during the hot-dry season in the zone.

The upper limit of DBT (36.71 ± 0.6°C), ranging from 35.0-39.0°C and recorded at 18:00 h and corresponding to THI of 33.0°C (31.40-35°C), shows that the value was remarkably higher than the DBT upper limit of 24-26°C of the thermoneutral (comfort) zone for poultry in the temperate environment [33,34]. The value was also outside the range of 18-26°C, reported for poultry, reared under tropical environmental conditions [32,35,36]. At 6:00 h the lowest DBT of 24.3 ± 0.5°C, corresponding to THI of 23.1°C, fell within the range of the upper limit reported for poultry, and it was the only DBT value recorded that was strictly within the comfort (thermoneutral) zone (Tables 2 and 3). Thus, the laying hens during the hot-dry season in the zone were reared under the DBT values that were predominantly outside the thermoneutral (comfort) zone, indicating that the thermoregulatory mechanisms of the laying hens may be overtasked in an attempt to ensure homeothermy [33,37]. Such impairment results in a down-turn in physiological and performance parameters of the laying hens, indicating that the ambient temperature may have negative influence on the wellbeing and productivity of the laying hens [38,39].

The heat stress observed from the study period corroborates the reports of Ayo et al. [31,40,41], who demonstrated the prevalence of heat stress in the zone during the hot-dry season. Oladele et al. [42] reported the deterrent effects of heat stress on biochemical parameters in avian species in the zone. Ayo et al. [43] documented some detrimental effects of heat stress on cloacal temperature and performance parameters of pullets in the zone. The present study shows that high ambient temperatures are inimical to egg production and supports the reports of Felva-Grant et al. [44], and Leinonen et al. [39], who demonstrated that high ambient temperature is a deterrent on fecundity in poultry. Obidi et al. [24,25] have demonstrated the deleterious effects of the hot-dry season on fertility and hatchability in breeder hens, and that the season depresses sperm concentration, motility and fertility in breeder cocks in the zone.

The observations on the panting behaviour of the laying hens corroborate the findings of Minka and Ayo [32] and Mack et al. [29,45], who reported panting in heat-exposed pullets and laying hens, respectively as a stressful behavioural response. The present study has shown that high ambient temperature, resulting in increase in thermal load in poultry, induced panting which was an indication of behavioural thermoregulatory response in the laying hens [44]. Such behavioural response to heat stress has been reported by Mack et al. [29,45], who demonstrated that laying hens subjected to heat stress spend less time feeding, but more time drinking and panting.

The results of the present study show that supplemental coadministration or individual inclusion of lycopene and vitamin E significantly supported fecundity in hens during the hot-dry season, when heat stress was prevalent. Similar results were obtained by Sahin et al. [28], Olson et al. [14] and Turk et al. [46], who demonstrated that lycopene and vitamin E enhance ovarian function during heat stress. Although there was no significant difference between the treatment groups, the antioxidant-administered laying hens recorded a relatively hen-day egg production than the control hens. The result, for the first time, has provided evidence on the beneficial role of the carotenoid lycopene and α-tocopherol in avian ovarian function and fertility. Few studies have demonstrated the significant potential of lycopene in enhancing immunity and reproductive efficiency in poultry [14,46]. The co-supplementation of lycopene and vitamin E to laying hens during the hot-dry season resulted in the highest hen-day egg production throughout the experimental period. The result shows that lycopene- and/ or vitamin E-treated laying hens maintained consistently hen-day production, amounting to over 6% weekly mean egg production, compared to the controls.

The results show that the rate of decline in hen-day egg production was mitigated in lycopene- and vitamin E-administered laying hens in comparison with the control hens. This was, apparently, irrespective of the deterrent associated with old age of the laying hens and the heat load acting on them during the hot-dry season. This finding supports the previous report on the antioxidant and/ or antistress activities of vitamin E and corroborated by Vazquez et al. [47], Lewis et al. [22] and Liu et al. [48], who reported the antistress and antiinflammatory effects of vitamin E in hens exposed to heat stress-induced conditions. Olson et al. [14] and Yardibi and Turkay [49], demonstrated the ameliorative effects of vitamin E on egg production, egg quality and nutrient utilisation in laying hens exposed to heat stress, thereby improving fertility and fecundity. The present study was conducted on laying hens, aged 41 weeks at the beginning of the study, when vital indices of fertility, including the rate of egg production and quality in hens normally start to decline due to age-related gonadal dysfunction and metabolic alterations, mediated by oxidative stress [19,50,51]. Such age-related ovarian functional depreciation is significantly associated with stress-mediated compromise in mitochondrial function due to the susceptibility of the ovarian structural lipoproteins to oxidative stress [52-54].

The results show that lycopene ameliorated the effect of heat stress on laying hens and improved hen-day egg production. Although the mechanism of action of lycopene was not elucidated in the present study, the reports of [55,56] demonstrated lycopene’s antioxidant activity in avian species and its beneficial biological intervention in stress-induced ovarian failure. Bakker et al. [55] showed the anti-inflammatory and antioxidative roles of a dietary mixture of vitamin E and lycopene. Since most physiological anomalies, including disease conditions and reproductive (gonadal) dysfunctions, are mediated by inflammatory and oxidative stress mechanisms, the findings of the present study on the role of lycopene and -αtocopherol in alleviating heat-induced stress and reproductive losses during the hot-dry season may also be due to their anti-inflamatory and, particularly, antioxidative properties [48,56].

The remarkable decrease in eggshell thickness and eggshell weight in control laying hens, suggests a decrease in calcium mobilisation and utilisation during the heat stress. The results corroborate previous reports [29,57-59] that heat-induced stress adversely affects qualitative indices of eggshell in laying hens. Eggshell quality is an important index of overall egg quality, associated with the efficiency of calcium mobilisation and deposition on eggshell in the process of egg formation. This physiological aptitude of the laying hens reduces during unfavuorable conditions, including excessive increase in environmental temperatures [18,60,61]. The results show that lycopene and vitamin E ameliorated the deleterious effects of heat stress on the laying hens in the zone, and that the antioxidants improved qualitative indices of the egg in the laying hens, exposed to environmental heat stress during the hot-dry season. The observation supports the reports of Olson et al. [14] and Sahin et al. [2,62] that lycopene supplementation alleviates heat-induced stress on performance parameters of domestic birds, including egg qualitative indices. Similar report by [63], demonstrated the beneficial effect of vitamin E on egg production, qualitative eggshell indices and integrity in breeder hens, subjected to high ambient temperature. The combined effect of vitamin E and lycopene in alleviation of stress indices in broiler chickens exposed to high oxidant conditions has been demonstrated by Lu et al. [64].

The results show that lycopene and/or vitamin E increased the eggshell weight starting from week 2 of administration and the increase was sustained at week 3 in lycopene+ vitamin E and lycopene groups; while at week 4 the increase occurred in all the antioxidant-treated groups, but higher in lycopene+ vitamin E, and vitamin E, compared to lycopene group. This result indicates that lycopene administration significantly increased eggshell weight compared to controls, but the increase was, apparently, more sustained in laying hens administered with vitamin E, followed by those given lycopene+ vitamin E, while the least occurred in lycopene group. The findings have shown that with increase in the duration of administration of antioxidants lasting five weeks, lycopene+ vitamin E exerted the most potent effect on the increase in eggshell weight, compared to lycopene or vitamin E group.

Conclusion

In conclusion, thermal environment conditions during the hotdry season in the Northern Guinea Savannah zone induced heat stress, adversely affecting laying hens. The thermal environmental conditions exerted negative effects on the laying hens via impairment in egg qualitative indices. Lycopene and vitamin E, especially their combination, alleviated the risk of adverse effects of heat stress on their productivity during the hot-dry season by increasing hen-day egg production and improving eggshell qualitative indices.

Ethics Approval

The husbandry and the conduct of the experiments on the laying hens were performed in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes (Council of Europe No 123, Strasbourg 1985). All the experimental protocols described were approved by the Ethics Review Committee for Animal Experimentation of Ahmadu Bello University, Zaria, Nigeria.

Conflict of Interest

References

1. Opoku EY, Classen HL, Scott TA. Effects of wheat distillers dried grains with solubles with or without protease and β-mannanase on the performance of turkey hen. Poult Sci. 2015;94(2):207-214.

   [Cross ref] [Google scholar] [PubMed]

2. Sahin K, Orhan C, Tuzcu M, Sahin N, Hayirli A, Bilgili S, et al. Lycopene activates antioxidant enzymes and nuclear transcription factor systems in heat-stressed broilers. Poult Sci. 2016; 95(5):1088-1095.

   [Cross ref] [Google scholar] [PubMed]

3. Surai PF, Kochish II, Romanov MN, Griffin DK. Nutritional modulation of the antioxidant capacities in poultry: the case of vitamin E. Poult Sci. 2019;98(9):4030-4041.

   [Cross ref] [Google scholar] [PubMed]

4. Quinteiro-Filho WM,  Ribeiro A,  Ferraz-de-Paula V,  Pinheiro ML,  Sakai M,  Sa LRM,  et al. Heat stress impairs performance parameters, induces intestinal injury, and decreases macrophage activity in broiler chickens. Poult Sci. 2010;89(9):1905-1914.

   [Cross ref] [Google scholar] [PubMed]

5. Troxell B. Salmonella enterica serovar Typhimurium utilizes the ClpPX and Lon proteases for optimal fitness in the caeca of chickens. Poult Sci. 2016;95(7):1617-1623.

   [Cross ref] [Google scholar] [PubMed]

6. Mirfenereski E, Johannian R. Effects of dietary organic chromium and vitamin C supplementation on performance, immune responses, blood metabolites, and stress status of laying hens subjected to high stocking density. Poult Sci. 2015;94(2):281-288.

   [Cross ref] [Google scholar] [PubMed]

7. Star L, Kemp B, van den Anker I, Parmentier HK. Effect of single or combined climatic and hygienic stress in four layer lines: 1. Performance. Poult Sci. 2008a; 87(6):1022-1030.

   [Cross ref] [Google scholar] [PubMed]

8. Star L, Decuypere  E, Parmentier HK, Kemp B. Effect of single or combined climatic and hygienic stress in four layer lines: 2. Endocrine and oxidative stress responses. Poult Sci. 2008b;87(6):1031-1038.

   [Cross ref] [Google scholar] [PubMed]

9. Rozenboim I, Mobarky N, Heiblum R, Chaiseha Y, Kang SW, Biran I, et al. The role of prolactin in reproductive failure associated with heat stress in the domestic turkey. Biol Reprod. 2004; 71(4):1208-1213.

   [Cross ref] [Google scholar]

10. Elnagar SA, Scheideler SE, Beck MM. Reproductive hormones, hepatic deiodinase messenger ribonucleic acid, and vasoactive intestinal polypeptide-immunoreactive cells in hypothalamus in the heat stress-induced or chemically induced hypothyroid laying hen. Poult Sci. 2010;89(9):2001-2009.

    [Cross ref] [Google scholar] [PubMed]

11. Dzenda T, Ayo JO, Lakpini CAM, Adelaiye ABM. Season, sex and live weight variations in feed and water consumption of adult captive African giant rat (Cricetomys Gambianus, Waterhouse-1840) kept individually in cages. J Anim Physiol Anim Nutri. 2013;97(3):465-474.

    [Cross ref] [Google scholar] [PubMed]

12. Boileau TW-M, Boileau AC, Erdman Jr, JW. Bioavailability of all-trans and cis-isomers of lycopene. Exp Biol Med. 2002;227(10):914-919.

    [Cross ref] [Google scholar] [PubMed]

13. Palozza P, Catalano A, Simone R, Cittadini A. Lycopene as a guardian of redox signaling. Acta Biochimica Polonica. 2012;59(1):21-25.

    [Google scholar] [PubMed]

14. Olson JB, Ward NE, Koutsos EA.Lycopene incorporation into egg yolk and effects on the laying hen’s immune function. Poult Sci. 2008;87(12):2575-2580.

    [Cross ref] [Google scholar] [PubMed]

15. Khan N, Afaq F, Mukhtar H. Cancer chemoprevention through dietary antioxidants: Progress and promise. Antioxid. Redox Signal. 2008;10(3):1-6.

    [Cross ref] [Google scholar] [PubMed]

16. Wang Y, Chung S, Marjorie L, McCullough WOS, Fernandez ML, Sung KI, et al. Dietary carotenoids are associated with cardiovascular disease risk biomarkers mediated by serum carotenoid concentrations. J Nutri. 2014;144(7):1067-1074.

    [Cross ref] [Google scholar] [PubMed]

17. Helmy MM, Senbel AM. Evaluation of vitamin E in the treatment of erectile dysfunction in aged rats. Life Sci. 2012;90(9):489-494.

    [Cross ref] [Google scholar] [PubMed]

18. Klasing KC, Korver DR. Nutritional diseases. (In Diseases of Poultry. D. E. Swayne, ed. 14th ed.) Wiley-Blackwell. 2020;1257-1285.
19. Surai PF, Fujihara N, Speake BK, Brillard JP, Wishart GJ, Sparks HNC, et al. Polyunsaturated fatty acids, lipid peroxidation and antioxidant protection in avian species-review. Asian-Austral J Anim Sci. 2001;14(7):1024-1050.

    [Cross ref] [Google scholar]

20. Surai PF. Antioxidants in poultry nutrition and reproduction: An update. Antioxid. 2020;9(2):105-107.

    [Cross ref] [Google scholar]

21. Lewis ED, Meydani SN, Wu D. Regulatory role of vitamin E in the immune system and inflammation. IUBMB Life. 2019;71(4):487-494.

    [Cross ref] [Google scholar] [PubMed]

22. Urso URA, Dahlke F, Maiorka A, Bueno IJM, Schneider AF, Surek D, et al. Vitamin E and selenium in broiler breeder diets: Effect on live performance, hatching process, and chick quality. Poult Sci. 2015; 94(5):976-983.

    [Cross ref] [Google scholar] [PubMed]

23. Dzenda T, Ayo JO,  Sinkalu V. O, Yaqub LS. Diurnal, seasonal, and sex patterns of heart rate in grip-restrained African Giant rats (Cricetomys gambianus, Waterhouse). Physiol Reports. 2015;3(10):e12581-12582.

    [Cross ref] [Google scholar] [PubMed]

24. Obidi JA, Onyeanusi BI, Rekwot PI, Ayo JO, Dzenda T. Seasonal variations in seminal characteristics of Shikabrown breeder cocks. Inter J Poult Sci. 2008a;7(12):1219-1223.

    [Cross ref] [Google scholar]

25. Obidi JA, Onyeanusi BI, Ayo JO, Rekwot PI, Abdullahi SJ. Effect of timing of artificial insemination on fertility and hatchability of Shikabrown breeder hens. Intern J Poult Sci. 2008b;7(12):1224-1226.

    [Cross ref] [Google scholar]

26. Zulovich JM, DeShazer JA. Estimating egg production declines at high environmental temperatures and humidities. ASAE Paper 1990;904021.

    [Google scholar]

27. Sun B, Chen C, Wang W, Ma J, Xie Q, Gao Y, et al. Effects of lycopene supplementation in both maternal and offspring diets on growth performance, antioxidant capacity and biochemical parameters in chicks. J Anim Physiol Nutri. 2014;99(1):42-49.

    [Cross ref] [Google scholar] [PubMed]

28. Sahin K, Sahin N, Onderci M. Vitamin E supplementation can alleviate negative effects of heat stress on egg production, egg quality, digestibility of nutrients and egg yolk mineral concentrations of Japanese quails. Res Vet Sci. 2002;73(3):307-312.

    [Cross ref] [Google scholar] [PubMed]

29. Mack LA, Felver-Gant JN, Dennis RL, Cheng HW.  Genetic variation alter production and behavioural responses following heat stress in 2 strains of laying hens. Poult Sci. 2013;92(2):285-294.

    [Cross ref] [Google scholar] [PubMed]

30. Vathana S, Kang K, Loan CP, Thinggaard G, Kabasa JD, ter Meulen U. Effect of vitamin C supplementation on performance of broiler chickens in Cambodia. Proc. Inter Conf Agric Res Devt. 2002.

    [Cross ref] [Google scholar]

31. Ayo JO, Owoyele OO, Dzenda T. Effects of ascorbic acid on diurnal variations in rectal temperature of Bovan Nera pullets during the harmattan season. Inter J Poult Sci. 2007;6(8):612-616.

    [Cross ref] [Google scholar]

32. Minka NS, Ayo JO. Behavioural and rectal temperature responses of Black Harco pullets administered vitamins C and E and transported by road during the hot-dry season. J Vet Behav. 2010;5(3):134-144.

    [Cross ref] [Google scholar]

33. Holik V. Management of laying hens to minimize heat stress. Lohmann Info. 44:16-29.

    [Google scholar]

34. Kinggori AM. Review of factors that influence egg fertility and hatchability in poultry. Intern J Poult Sci. 2009;10(6):16-29.

    [Cross ref] [Google scholar]

35. Oluyemi, JA, Roberts PA. Poultry Production in the Warm Wet Climates. Spectrum Book Limited.2000;103-108.

    [Google scholar]

36. Fernandes JM, Scapini LB, Gottardro ET, Burin Jr AB, Marques FE, Gruchouskei L, et al. Thermal conditioning during the first week on performance, heart morphology and carcass yield of broilers submitted to heat stress. Acta Sci. 2013;35(3):311-313.

    [Google scholar]

37. Altan O,   Pabuçcuoğlu A,   Altan A,   Konyalioğlu S,   Bayraktar H. Effect of heat stress on oxidative stress, lipid peroxidation and some stress parameters in broilers. British Poult Sci. 2003;44(4):545-550.

    [Cross ref] [Google scholar] [PubMed]

38. Ayo JO, Obidi JA, Rekwot PI. Effects of heat stress on the well-being, fertility and hatchability of domestic chickens in the Northern Guinea Savannah zone of Nigeria: a review. International Scholarly Res Network Vet Sci. 2011.Cross ref]

    [Google scholar]

39. Leinonen I, Williams AG, Kyriazakis I. The effects of welfare-enhancing system changes on the environmental impacts of broiler and egg production. Poult Sci. 2014;93(2):256-266.

    [Cross ref] [Google scholar] [PubMed]

40. Aluwong T, Sumanu VO, Ayo JO, Ocheja BO, Zakari FO, Minka NS. Daily rhythms of cloacal temperature in broiler chickens of different age groups administered with zinc gluconate and probiotic during the hot-dry season. Physiol Reports. 2017.

    [Cross ref] [Google scholar] [PubMed]

41. Makeri HK, Ayo JO, Aluwong T, Minka NS. Daily rhythms of blood parameters in broiler chickens reared under tropical climate condition. J Circad Rhythms. 2017;15(1):1-8.

    [Cross ref] [Google scholar] [PubMed]

42. Oladele SB, Ogundipe S, Ayo JO, Esievo KAN. Seasonal and species variations in erythrocyte osmotic fragility of indigeneous poultry species in Zaria, Northern Guinea Savannah zone of Nigeria. Bull. Anim. Health Prod. Africa. 2003;51:204-214.
43. Ayo JO, Danbirinin S, Egbuniwe IC, Sinkalu VO. Cloacal temperature responses and some performance indices in Black Harco pullets administered with betaine during the hot-dry season. J Vet. Sci Tech. 2014a;5(2):6-8.

    [Cross ref] [Google scholar]

44. Felver-Gant JN, Mack LA, Dennis RL, Eicher SD, Cheng HW. Genetic variations alter physiological responses following heat stress in 2 strains of laying hens. Poult Sci. 2012;91(7):1542-1551.

    [Cross ref] [Google scholar] [PubMed]

45. Mack LA, Felver-Gant JN, Dennis RL, Cheng HW. Effects of heat stress on egg production and quality in two strains of laying hens. Poult Sci. 2010;87(1):120.

    [Cross ref] [Google scholar]

46. Turk G, Ceribasi AO, Sakin F, Sonmonz M, Atessahin A. Antiperoxidative and anti-apototic effects of lycopene and ellagic acid on cyclophosphamide-induced testicular lipid peroxidation and apoptosis. Reprod Fertil Devt. 2010;22(4):587-596.

    [Cross ref] [Google scholar] [PubMed]

47. Vazquez JR, Gomez VG, Lopez CC, Cortes AC, Díaz AC, Fernandez SRT, et al. Effects of 25-hydroxycholecalciferol with two D3 vitamin levels on production and immunity parameters in broiler chickens. J Anim Physiol Anim Nutr (Berl). 2018;102(3):e493-e497.

    [Cross ref][Google scholar] [PubMed]

48. Liu YJ, Zhao LH, Mosenthin JY, Zhang C, Ji R, Ma QG. Protective effect of vitamin E on laying performance, antioxidant capacity, and immunity in laying hens challenged with Salmonella enteritidis. Poult Sci. 2019;98(11):5847-5854.

    [Cross ref] [Google scholar] [PubMed]

49. Yardibi H, Turkay C. The effects of vitamin E on the antioxidant system, egg production and egg quality in heat stressed laying hens. Turk J Vet Anim Sci. 2008;32(5):319-325.

    [Google scholar]

50. Romero-Sanchez H, Plumstead H, Brake J. Feeding broiler breeder males.1 Effect of feeding program and dietary crude protein during rearing on body weight and fertility of broiler breeder males. Poult Sci. 2007;86(1):168-174. .

    [Cross ref] [Google scholar] [PubMed]

51. Surai PF. Natural antioxidants in poultry nutrition: new developments. 16th European Symposi.  Poult Nutri. 2009;9(2):669-676.

    [Cross ref] [Google scholar] [PubMed]

52. Burstein E, Perumalsamy A, Bentov Y, Esfandiari N, Jurisicova A, Casper RF, et al. Co-enzyme Q10 supplementation improves ovarian response and mitochondrial function in aged mice. Fertil Steril.  2009;92(3):887-895.

    [Cross ref] [Google scholar] [PubMed]

53. Bentov Y, Yavorska T, Esfandiari N, Jurisicova A, Casper RF. The contribution of mitochondrial function to reproductive aging. J. Assist. Reprod Genetics. 2011;28(9):773-783.

    [Cross ref] [Google scholar] [PubMed]

54. Ben-Meir A,  Burstein E,  Alvarez AB, Chong J,  Wong E,  Yavorska T, et al. Coenzyme Q10 restores oocyte mitochondrial function and fertility during reproductive ageing. Ageing Cell. 2015;14(5):887-895.

    [Cross ref] [Google scholar] [PubMed]

55. Bakker GCM, van Erk MJ, Pellis L, Wopereis S, Rubingh CM, Cnubben NHP, et al. An antiinfammatory dietary mix modulates inflammation and oxidative and metabolic stress in overweight men: a nutrigenics approach. American J Clin Nutri. 2010;91(4):1044-1059.

    [Cross ref] [Google scholar] [PubMed]

56. Pitargue FM, Kim JH, Goo D, Delos Reyes JB, Kil DY. Effect of vitamin E sources and inclusion levels in diets on growth performance, meat quality, alpha-tocopherol retention, and intestinal inflammatory cytokine expression in broiler chickens. Poult Sci. 2019;98(10):4584-4594.

    [Cross ref] [Google scholar] [PubMed]

57. Lin H, Mertens K, Kemps B, Govaerts T, De Ketelaere B, De Baerdemaeker J, et al. New approach of testing the effect of heat stress on eggshell quality: Mechanical and material properties of eggshell and membrane. British Poult Sci. 2004;45(4):476-482.

    [Cross ref] [Google scholar] [PubMed]

58. Pereira DF, Vitorasso G, Oliveira SC, Kakimoto SK, Togashi CK, Soares NM, et al. Correlations between thermal environment and egg quality of two layer commercial strains. Brazilian J Poult Sci. 2008;10(2):81-88.

    [Cross ref] [Google scholar]

59. Melesse A, Maak S, von Lengerken K. Effect of long-term heat stress on egg quality traits of Ethiopian naked neck chickens and their F1 crosses with Lohmann White and New Hampshire chicken breeds. Livest Res Rural Devt. 2010;22.

    [Google scholar]

60. Hafeez A, Mader A, Ruhnke I, Manner K, Zentek J. Effect of feed grinding methods with and without expansion on prececal and total tract mineral digestibility as well as on interior and exterior egg quality in laying hens. Poult Sci. 2016;95(1):62-69.

    [Cross ref] [Google scholar] [PubMed]

61. Lee GY, Han SN. The role of vitamin E in immunity. Nutrients. 2018;10(11):1614.

    [Cross ref] [Google scholar] [PubMed]

62. Sahin N, Orhan C, Tuzcu M, Sahin K, Kucuk O. The effects of tomato powder supplementation on performance and lipid peroxidation in quail. Poult Sci. 2008;87(2):276-283.

    [Cross ref] [Google scholar] [PubMed]

63. Scheideler SE, Weber P, Monsalve D. Supplemental vitamin E and selenium effects on egg production, egg quality, and egg deposition of α-tocopherol and selenium. J Appl Poult Res. 2010;19(4):354-360.

    [Cross ref] [Google scholar]

64. Lu T, Harper AF, Zhao J, Dalloul RA. Effects of a dietary antioxidant blend and vitamin E on growth performance, oxidative status, and meat quality in broiler chickens fed a diet high in oxidants. Poult Sci. 2014;93(7):1649-1657. .

    [Cross ref] [Google scholar] [PubMed]