This review examined the influence of environmental heat stress, a concern facing modern broiler producers, on protein metabolism and broiler performance, as well as the physiological mechanisms that activate and control or minimize the detrimental impacts of stress. In addition, available scientific papers that focused on amino acids (AA) digestibility under stress conditions were analyzed. Furthermore, AA supplementation, a good strategy to enhance broiler thermotolerance, amelioration, or stress control, by keeping stress at optimal levels rather than its elimination, plays an important role in the success of poultry breeding. Poultry maintain homeothermy, and their response to heat stress is mainly due to elevated ambient temperature and the failure of effective heat loss, which causes a considerable negative economic impact on the poultry industry worldwide. Reduced feed intake, typically observed during heat stress, was the primary driver for meat production loss. However, accumulating evidence indicates that heat stress influences poultry metabolism and endocrine profiles independently of reduced feed intake. In conclusion, high ambient temperatures significantly reduced dietary AA intake, which in turn reduced protein deposition and growth in broilers. Further studies are required to determine the quantity of the AA needed in warm and hot climates and to introduce genetic tools for animal breeding associated with the heat stress in chickens.

The anticoccidial influences of various amounts of Cinnamomum verum powder were compared with that of salinomycin as standard synthetic anticoccidial drug on the anticoccidial indicators and production performance in broilers experimentally exposed to coccidiosis. Broiler chicks at 1 d of age (n = 150) were arbitrarily distributed into 6 groups. Birds from groups 1-3 were received the starter and finisher diets plus 2, 4, and 6 g of cinnamon/kg of the diet, respectively. Birds from group 4 were fed the starter and finisher diets plus 66 mg of salinomycin, group 5 constituted the positive control (PC), with the coccidial challenge, and group 6 constituted the negative control (NC), without the coccidial infection, which were both maintained on diets without any cinnamon. The results showed that BW gain, feed conversion ratio, and production efficiency factor declined considerably (P < 0.05) in the PC compared with the NC. At seventh day postinfection (DPI), the lesion score was significantly (P < 0.05) lower in the ceca of salinomycin-treated birds than the PC. The anticoccidial index was moderate in the chickens treated with salinomycin and 6 g cinnamon at 7 DPI compared with those in the PC group. In addition, cinnamon- or salinomycin-treated birds exhibited lower oocyst values and higher oocyst reduction rate than those in the PC. We concluded that C. verum at level 6 g cinnamon/kg diet moderately reduced coccidiosis and attempted to improved BW, feed conversion ratio, and production efficiency at 7 DPI compared with the infected groups.

Ross 308 broiler chicks (n = 240) aged 1 day were assigned to five groups for eight replicates (six chicks for each) (3♂ and 3♀). Basal dietary groups were supplemented by 2000, 4000, and 6000 mg/kg cinnamon (CN) for 21 days. Basal diet alone was used as a negative control, and basal antibiotic diet (Colimox) was used as a positive control. At 10, 14, and 21 days of age, chicks that received 2000 mg CN and Colimox had a higher body weight, resulting in an increase in body weight gain. CN also resulted in the maximum improvement in the feed conversion ratio and feed efficiency over 1–21 days at the level of 2000 mg/kg. At days 10, the maximum relative breast weight was 2000 mg/kg of CN. Mean serum albumin concentrations, duodenal villus height, and goblet cell density increased (p < 0.05) by 2000 mg/kg of CN, and mean serum globulin and total protein concentrations and crypt depth increased (p < 0.05) by 6000 mg/kg of CN compared with control. Increased cecal Escherichia coli number was CN dose-dependent. In conclusion, dietary inclusion of 2000 mg/kg CN can be applied as an alternative to in-feed antibiotics for broiler starter diet.

A total of 192 one-day-old Ross 308 broiler chicks were assigned to 4 treatments with 8 replicate cages of 6 chicks (3♀ and 3♂) per cage according to a completely randomized block design. The dietary treatments were a basal diet (control) and a control diet supplemented with 1,000, 3,000, and 5,000 mg/kg Rumex nervosus leaves meal (RN). Gallic acid and some volatile compounds were detected in the RN extract. On day 10 of age, BW was improved (P = 0.016) with supplemental RN (1,000–5,000 mg/kg). On day 14 of age, dietary application of RN up to 3,000 mg/kg increased BWG (P = 0.003) compared with control, while a 1,000 mg/kg RN had the best feed conversion ratio (P = 0.016). On day 10 of age, samples were taken on a single female bird per replicate. The addition of RN (1,000–5,000 mg/kg) increased (P < 0.001) serum albumin and triiodothyronine levels and maximized the relative weight of breast meat (P = 0.003). Feeding a diet with 1,000 mg/kg RN resulted in greater duodenal villus height (P < 0.001) than control and the diet with 5,000 mg/kg RN. Broilers fed diet supplemented with 1,000 mg/kg RN had the best duodenal villus surface area (P < 0.001). Feeding a diet with 1,000 mg/kg RN decreased (P < 0.001) cecal Escherichia coli count compared with control and the diet with 5,000 mg/kg RN. Salmonella spp. count tended to increase with 5,000 mg/kg RN leaves meal (P = 0.069, linear P = 0.026). In conclusion, R. nervosus leaves meal could be considered as a phytogenic feed additive in broiler diets up to a 1,000-mg/kg inclusion rate because of its combined positive effects on BWG, feed conversion ratio, villus height, villus surface area, serum albumin and triiodothyronine hormone, and cecal E. coli during the starter period (day 10–14 of age). Further study is required to elucidate its molecular mechanism.

Veterinarians and animal producers use non-essential compounds via either feed additives or implantation for a long history as growth promoters for farm animals. These compounds, such as anabolic hormones, bovine somatotropin, Beta-agonists, have multiple positive effects and improve animal performance in many meat-exporting countries due to their anabolic activity. However, some of them may cause carcinogenic effects to the consumer. Anabolic hormones are now permitted to be used as growth promoters on a global scale, but have not been permitted in the EU since 1988. Unlawfully, drugs are sometimes added to farm animal feeds to improve muscle growth, feed utilization efficiency, milk production, and nitrogen retention in order to obtain an economic benefit in a shorter period.. In this article, we review the current knowledge on the safety and hazard of an anabolic compound as endocrine disruptor, not only on food, animals and public health but also on the environment, to arrive at recommendations for risk management and avoidance. The U.S. Food and Drug Administration approves seven hormone drugs (testosterone propionate, trenbolone acetate, estradiol, zeranol, progesterone, melengestrol acetate, and bovine somatotropin) for use in food animals for many purposes. Synthetic hormones were higher stability and longer persistence in the environment.