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There has been an unprecedented increase in global animal production, especially in subtropical and tropical areas in the last two decades (Renaudeau et al., 2012). The increase in the demand for food is due to a rise in human population (Godfray et al., 2010). Due to its potential role to provide food and livelihood securities (Paswan et al., 2014), poultry production, especially broiler production, are expected to meet the critical shortage in animal protein needed by Africa (Hatab et al., 2019).There has been growing concerns on the impacts of climate change on livestock production. For example, in West Africa, the expected increase in average temperature by 2°C-6°C by the year 2100 (Sylla et al., 2016) portends a serious challenge to sustainable broiler production. Due to the climatic challenge, heat stress events are expected to become more frequent in livestock species (Rahimi et al., 2020). A study by Tawfeek et al. (2014) showed that high ambient temperature adversely affected the performance of broiler chickens under high ambient temperature. However, the authors indicated that supplementation of antioxidants ameliorated the effects of thermal stress on the birds. Therefore, the diets of the birds are required to be adjusted to the climatic conditions (Attia & Hassan, 2017;Nir, 1992;Suganya et al., 2015) and also to the prevailing economic status of the countries where they are produced.The fast rate of development of the poultry production in tropical countries has also engendered a situation of overdependence on

The objective of this study was to investigate the effects in ovo injection of black cumin (BC) extract on chick's quality and response of thermally challenged broiler chickens. A total of 700 hatching eggs of broiler chickens (Marshall) were assigned to 7 treatments of 100 eggs each and incubated using the conventional protocol (37.8°C) for the first 10 d and then exposed to a high temperature (39.6°C) for 6 h daily from day 10 until day 18 of the incubation. At embryonic day 17.5, the eggs were randomly allotted to 7 treatment groups, viz.: eggs without in ovo injection (WA), eggs injected with 0.9% saline solution (SA), 3 mg ascorbic acid (AA), 2 mg BC (TB), 4 mg BC (FB), 6 mg BC (SB), and 8 mg BC (EB) extracts. Experiment was laid out in a Completely Randomized Design. After hatching, the chicks were reared separately according to in ovo treatments for 8 wk. Data were collected on hatchability, chick quality, internal organs, growth performance, plasma superoxide dismutase, malondialdehyde, and triiodothyronine (T 3 ). The results showed that the hatchability of the eggs in the AA group was similar to that of SB eggs and higher than that of the other treatment groups. The intestinal weights of SB and EB birds were significantly higher ( P < 0.05) than those of TB, SA, and WA. The final weights of the birds of SB and AA were higher ( P < 0.05) than those of other treatments. The feed conversion ratio of the birds of TB and FB was comparable to that of EB and WA but higher than that of SB and AA. At hatch, the creatinine of the birds in SA and WA was similar to that of EB, FB, and TB but higher ( P < 0.05) than that of AA and SB. Also, the plasma malondialdehyde, T 3 , and superoxide dismutase of SB and AA birds were better ( P < 0.05) than those of the control groups. Overall, it was concluded that 6 mg of BC extract improved the antioxidant status and posthatch performance of thermally challenged broiler chickens.

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Growing broilers were offered either 0 (0H), 10 (10H), 20 mL (20H) honey, or 0.5 g vitamin C/litre water (AA) during hot-dry season. Honey had no significant (P > 0.05) effect on feed intake (FI), weight gain (WG), feed conversion ratio (FCR), water intake (WI), survival (SURV), dressed percentage (DRE), breas tmeat (BRE), gizzard (GIZ), drumstick (DRU), shank (SHA), thigh (THI), tibia volume (VOL), and magnesium (MAG). Effect of honey was significant (P < 0.05) on tibial weight (WEI), density (DEN), calcium (CAL), and phosphorus (PHO). WEI and DEN increased with increasing level of honey. 20H broilers had higher CAL than 0H and 10H groups. Broilers offered honey had significantly lower PHO than AA group but the difference between honey groups was not significant. Honey significantly affected PR (P < 0.001) and HR (P < 0.001) but not RT (P > 0.005). Higher dose of honey lowered PR and HR. Honey significantly (P < 0.05) increased THY but LIV, KID, LUN, SPL, BUR, and HEA were not significantly (P > 0.05) affected. 20H broilers had higher THY than 0H and 10H groups. In conclusion, honey did not affect growth but might improve broilers' welfare when offered up to 20H during hot periods.

Dietary manipulation has been seen as one of the practical ways to ameliorate the adverse effects of thermal stress in the hot humid tropical climate. In order to investigate the influence of Curcuma longa (turmeric) rhizome powder on physiological responses and performance under hot humid tropical climate, 240 broiler chicks were randomly assigned to four dietary treatments having four replicates of 15 birds each in a complete randomized design. Broiler birds were fed basal diets and supplemented with 0 (CT), 4 (TG), 8 (FT), and 12 g (SG) of turmeric powder/kg of diet for 8 weeks. Data were collected weekly on feed intake and body weights. Blood samples were collected from eight birds per treatment at week 4 (starter phase) and week 8 (finisher phase) of the experiment for the determination of plasma 3,5,3'-triiodothyronine (T), superoxide dismutase (SOD), malondialdehyde (MDA). Rectal temperature of the birds was also taken. At 56 days of age, eight birds from each treatment were slaughtered for the determination of relative organ weights. Results showed that the final weights of the birds in FT were significantly higher than those of the birds in TG, SG, and CT. The weight gain of the birds in FT was higher than those of the birds in SG while those of SG were higher than those of TG whose values were higher than that of CT. The feed conversion ratio of the broiler chickens in CT was higher (P < 0.05) than those of other treatment groups while the birds in FT and SG had similar feed conversion ratios. SOD of birds fed turmeric rhizome powder was higher than the birds in the control group at both starter and finisher phases. Furthermore, MDA of the birds in FT was lower than those of the birds in the other treatment groups at the finisher phase. Plasma T was higher in the birds fed turmeric at the finisher phase than chickens in the control group. There was no difference in the rectal temperatures of the birds. To conclude, turmeric rhizome powder improved the physiological response and performance of broiler chicken under hot humid tropical climate in a dose-dependent characteristic and the optimum supplementation rate of 8 g/kg of diet was recorded.

Heat stress (HS) is an important environmental stress factor affecting poultry production on a global scale. With the rise in ambient temperature and increasing effects of global warming, it becomes pertinent to understand the effects of HS on poultry production and the strategies that can be adopted to mitigate its detrimental impacts on the performance, health, welfare, immunity, and survival of birds. Amino acids (AAs) have been increasingly adopted as nutritional modifiers in animals to ameliorate the adverse effects of HS. They are essential for protein synthesis, growth, maintenance, reproduction, immunity, stress response, and whole-body homeostasis. However, HS tends to adversely affect the availability, transport, absorption, and utilization of these AAs. Studies have investigated the provision of these AAs to poultry during HS conditions, and variable findings have been reported. Taurine, L-theanine, and L-citrulline are non-essential amino acids that are increasingly gaining attention as nutritional supplements in HS animals. Similarly, betaine is an amino acid derivative that possesses favorable biological properties which contributes to its role as a functional additive during HS. Of particular note, taurine is negligible in plants, while betaine, L-theanine, and L-citrulline can be found in selected plants. These nutrients are barely found in feed ingredients, but their supply has been shown to elicit important physiological roles including anti-stress effects, anti-oxidative, anti-inflammatory, gut promoting, and immunomodulatory functions. The present review provides information on the use of these nutritionally and physiologically beneficial nutrients as functional additives to poultry diets during HS conditions. Presently, although several studies have reported on the positive effects of these additives in human and murine studies, however, there is limited information regarding their utilization during heat stress in poultry nutrition. Therefore, this review aims to expound on the functional properties of these nutrients, their potentials for HS alleviation, and to stimulate further researches on their biological roles in poultry nutrition.

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