Dietary arginine responses of Ross 708 broilers reared under cyclic elevated temperatures

Overall, the results of this study indicate that in addition to improving feed efficiency and 48-day processing yields, dietary Arg may also influence core body temperature in a dose-dependent manner in broilers subjected to a cyclic HS challenge. This may be due to the role of Arg in vasodilation and the alleviation of oxidative stress.

Arginine (Arg) is an amino acid considered to be essential for poultry and conditionally essential for humans. Due to its metabolic role in the regulation of health and growth, it is considered a “functional” amino acid that has extensive metabolic roles beyond protein synthesis and accretion (Wu, 2009; Castro and Kim, 2020). Specifically, Arg is a precursor for the synthesis of many molecules including nitric oxide, proline, hydroxyproline, polyamines, glutamine, ornithine, and creatine (Khajali and Wideman, 2010). Therefore, it is involved in many important biological and physiological roles including immune function, wound healing, vasodilation, and alleviation of oxidative stress (Wideman et al., 1995; Murrell et al., 1997; Atakisi et al., 2009; D’Amato and Humphrey, 2010; Khajali and Wideman, 2010; Fouad et al., 2012).

Heat stress (HS) is a common environmental stressor that results in substantial negative effects on animal welfare, growth performance, and carcass characteristics (Geraert et al., 1996; Sandercock et al., 2001; Song and King, 2015; Rostagno, 2020), and significant economic losses to the global broiler industry. Heat stress occurs when the amount of heat energy produced by the animal exceeds the amount of net energy being dissipated from the animal’s body (Lara and Rostagno, 2013). Genetic selection of modern broiler genotypes has made them more sensitive to elevated temperatures, which has been suggested in part due to increased metabolic activity that causes a greater production of body heat (Settar et al., 1999; Lara and Rostagno, 2013). Nutritional manipulation is one of the several management strategies that can be used to help alleviate this condition.

Arg has previously been shown to influence the performance of birds subjected to HS, with higher ratios improving FCR and increasing breast meat yield. Brake et al. (1994a,b) suggested that the dietary Arg requirement during hot temperatures may be higher compared to at ambient temperatures because Arg availability from dietary sources is decreased, or its metabolic requirement is increased, or both. Decreased availability may be caused bychanges in gut morphology and integrity, amino acid absorption, or intestinal microbiota, while an increased metabolic requirement could be caused by higher production of reactive oxygen species and a higher level of lipid peroxidation that occurs in heat-stressed chickens (Brake et al., 1998; Yang et al., 2010; Rostagno, 2022). With these mechanisms in mind, the application of Arg to ameliorate the effects of HS and improve broiler growth performance has gained strong interest from the poultry industry.

METHODS
Male Ross 708 broiler chicks were weighed by group to determine the average overall body weight and allotted to 48 floor pens. All pens contained used pine litter top-dressed with fresh shavings and were equipped with a single commercial-type pan feeder and nipple waterers to provide free access to feed and clean water throughout the trial. Supplemental waterers and chick pan feeders were placed in each pen from 0 to 7 d post-hatch to facilitate access to feed and water for young chicks. Broilers were fed diets in four phases that included a common starter phase (0 – 17 d), a common grower phase (17 – 27 d), an experimental finisher 1 phase (27 – 38 d), and an experimental finisher 2 phase (38 – 46 d). Diets were formulated using ingredients that were analyzed prior to formulation in order to achieve target amino acid concentrations. The common starter and common grower diets were corn and soybean meal-based and formulated to meet or exceed the primary breeder nutrient recommendations. The finisher 1 and finisher 2 formulations were designed to be nutritionally complete and meet primary breeder recommendations except for Arg concentration. Six dietary treatments of digestible Arg: Lys ratios of 80, 92, 104, 116, 128, 140 were utilized. The starter diets were pelleted and crumbled, while the other diets were fed as pellets. Barn temperature was set to 32°C and decreased gradually throughout the trial to maintain bird comfort. On d 28, a cyclic HS program was employed where barn temperature was maintained at 32°C for 12 h daily (7:30 h to 19:30 h) and reduced to 24°C each night. This model was intended to mimic the cyclic HS experienced naturally by birds in the field, and was successful in inducing moderate HS as indicated by increased panting, modified bird behavior (leg extension), and increased core body temperature during each daily rise in barn temperature. Core body temperature was measured by cloacal temperature readings taken at 32, 39, and 46 d at both 6:00 h (before daily heat was applied) and 14:00 h (during peak daily heat application). Feeder and bird pen weights were recorded at 0, 17, 27, 38, and 46 d to determine growth performance, body weight, body weight gain (BWG), feed intake (FI), and mortality-corrected feed conversion ratio (FCR) for each feeding phase and cumulatively. Feed intake was calculated based on number of bird days to account for mortality. At the end of the trial, eight birds per pen were randomly selected, wing-banded, and marked for processing at 48 d at the Fortenberry Processing Plant at the Charles C. Miller Poultry Research Center at Auburn University. After an overnight chill, carcasses were deboned to collect weights of the pectoralis major (P. major) and minor (P. minor) muscles, wings, thighs, and drums. Total breast meat was calculated as the sum of the P. major and P. minor weights, and the yield of each part was determined by division of the part weight by the individual live weight taken the afternoon before the day of processing.

RESULTS
During both finisher 1 and finisher 2 phases, feed conversion ratio improved linearly (P = 0.001 and 0.012, respectively) as the ratio of Arg:Lys in the diet increased. Core body temperature increased by 1.6°C on average from readings taken prior to daily heat application (6:00 h) and at peak daily temperature (14:00 h) (Table 1). At both 32 and 39 d, 14:00 h core body temperature exhibited a quadratic relationship (P = 0.022 and 0.021, respectively) with dietary Arg, with the lowest numerical temperature observed for birds fed the diet with 116 Arg. At 46 d, the relationship between body temperature and Arg decreased linearly (P = 0.011) with a trend towards a quadratic relationship (P = 0.087).

Increasing Arg:Lys ratio in the diet resulted in several statistically significant responses in processing characteristics (Table 2). Chilled carcass weight exhibited a quadratic (P = 0.034) relationship with Arg level while chilled carcass yield exhibited a linear (P = 0.006) increase. In addition, both breast fillet weight and yield had a quadratic (P = 0.007 and 0.018, respectively) relationship with increasing Arg, with the numerically highest weight and yield achieved with the Arg:Lys ratio of 128 and 116, respectively. Tender weight showed a quadratic (P = 0.040) relationship with Arg as well, numerically increasing up to the Arg ratio of 128. Tender yield linearly (P = 0.038) increased with dietary Arg:Lys ratio. As expected with these responses in both breast fillets and tenders, total breast weight and yield also exhibited quadratic (P = 0.009 and 0.023, respectively) relationships with Arg, reaching the numerically highest values of 0.837 kg and 26.82% at Arg:Lys ratios of 128 and 116, respectively. Drum yield decreased quadratically (P = 0.031) as Arg ratio increased, presumably at the benefit of breast meat. The lowest numerical value for drum yield was measured at an Arg ratio of 128.

DISCUSSION
The Arg:Lys ratio recommended by the primary breeder to optimize growth performance for as-hatched Ross broilers is 108 from 25 – 39 d (finisher 1 phase) and 110 from 40 – 51 d (finisher 2 phase) (Aviagen Inc., 2022). The titration used in the current study captured a range of Arg:Lys ratios well below and above these values. In our study, the fact that FCR improved in a linear fashion as Arg ratio increased in conditions of cyclic HS suggests that FCR may have been optimized at Arg ratios greater than 140. Previous studies have also reported similar trends where increased Arg in the diet was associated with improved FCR during HS conditions. For example, Mendes et al. (1997) reported that FCR decreased from 1.955 to 1.912 when broilers were fed 110 and 140 Arg:Lys, respectively, from 21 to 42 d. Brake et al. (1998) showed a significant improvement in FCR between heat-stressed broilers fed a 136 ratio of Arg:Lys compared to a 109 ratio that was not significant between thermoneutral controls. Alternatively, Chamruspollert et al. (2004) reported a quadratic relationship of FCR with Arg for 7 to 21 d old chicks raised in constant HS as the dietary ratio increased in six increments of Arg:Lys ratio from 79 to 121.

Although we saw a linear improvement in feed efficiency as Arg:Lys ratio increased, there was no response to Arg in body weight gain. Though there was no thermoneutral control in our current trial, it is a reasonable hypothesis that the cyclic HS muted some of the effects of Arg on weight gain and that Arg was prioritized for other metabolic functions beyond muscle protein synthesis to ameliorate the effects of HS. Brake et al. (1998) noticed only a numerical increase in weight gain between two groups of 20 to 41 d old birds fed a diet of 109 or 136 Arg:Lys and subjected to HS, while a significant increase was observed between the two groups of thermoneutral controls. Conversely, a study by Chamruspollert et al. (2004) reported a quadratic relationship of BWG with increasing Arg ratios of 79 to 121, but this was determined in 7 to 21 d-old chicks reared in constant 35°C HS.

Cloacal temperature measurements taken in the current study show that dietary Arg:Lys ratio can influence the broiler’s ability to regulate body temperature under conditions of HS. Additionally, the quadratic response at 32 and 39 d compared with the linear response at 46 d suggests that the requirement to facilitate optimal thermoregulation may change with age. Arg likely influences body temperature through its role as a precursor to nitric oxide, a primary regulator of cutaneous vasodilation and blood flow (Moncada and Higgs, 1993; Steiner and Branco, 2001).

Dietary Arg level has also been shown to have effects on processing characteristics, most commonly influencing breast meat yield, leg meat yield, and carcass abdominal fat (Fouad et al., 2012). However, the influence of Arg level on processing characteristics during HS is less well documented. Still, some researchers have shown improved breast meat yield with increased Arg even when broilers were subjected to HS during the growing period (Mahmoud et al., 1996; Esser et al., 2017). Under thermoneutral conditions, the increase in breast meat yield has been shown to be at least in part at the expense of wing yield (Al-Daraji and Salih, 2012). In the current study, we found no influence on wing yield but rather a decrease in drum yield as dietary Arg and breast meat yield increased. Identifying processed parts that are either maximized or minimized in yield at certain Arg:Lys ratios can help producers make decisions to balance profit with cost of feed.

CONCLUSION
These data demonstrate that feed conversion and processing characteristics of Ross 708 male broilers are responsive to dietary Arg under cyclic HS conditions. Core body temperature was also influenced by Arg:Lys ratio under HS at each time point measured, providing evidence of metabolic roles of Arg beyond protein synthesis and accretion (i.e., vasodilation and alleviation of oxidative stress).

References
1. A l-Daraji, H. J., and A. M. Salih. 2012. Effect of dietary L-arginine on carcass traits of broilers. Res. Opin. Anim. Vet. Sci. 2:40 – 44.
2. Atakisi, O., E. Atakisi, and A. Kart. 2009. Effects of dietary zinc and l-arginine supplementation on total antioxidants capacity, lipid peroxidation, nitric oxide, egg weight, and blood biochemical values in Japanese quails. Biol. Trace Elem. Res. 132:136 – 143.
3. Aviagen Inc. 2022. ROSS Broiler: Nutrition Specifications. Aviagen, Huntsville, AL.
4. Brake, J., D. Balnave, and J. J. Dibner. 1994a. Wide arginine:lysine ratio ameliorates effect of heat stress in broilers. Poult. Sci. 73:74 – 82.
5. Brake, J., D. Balnave, and J. J. Dibner. 1998. Optimum dietary arginine:lysine ratio for broiler chickens is altered during heat stress in association with changes in intestinal uptake and dietary sodium chloride. Br. Poult. Sci. 39:639 – 647.
6. Brake, J., P. Ferket, J. Grimes, D. Balnave, I. Gorman, and J. J. Dibner. 1994b. Optimum arginine:lysine ratio changes in hot weather. Pages 82-104 in Proc. 21st Annu. Caroli na Poult. Nutr. Conf. North Carolina State University, Raleigh, NC.
7. Castro, F. L. D. S., and W., K. Kim. 2020. Secondary functions of arginine and sulfur amino acids in poultry health. Animals. 10:2106.
8. Chamruspollert, M., G. M. Pesti, and R. I. Bakalli. 2004. Influence of temperature on the arginine and methionine requirements of young broiler chicks. J. Appl. Poult. Res. 13:628 – 638.
9. D’Amato, J. L., and B. D. Humphrey. 2010. Dietary arginine levels alter markers of arginine utilization in peripheral blood mononuclear cells and thymocytes in young broiler chicks. Poult. Sci. 89:938 – 947.
10. Esser, A. F. G., D. R. M. Gonçalves, A. Rorig, A. B. Cristo, R. Perini, and J. I. M. Fernandes. 2017. Effects of guanidionoacetic acid and arginine supplementation to vegetable diets fed to broiler chickens subjected to heat stress before slaughter. Rev. Bras. Cienc. Avic. 19:429 – 436.
11. Fouad, A. M., H. K. El-Senousey, X. J. Yang, and J. H. Yao. 2012. Role of dietary l-arginine in poultry production. Int.J. Poult. Sci. 11:718-729.
12. Geraert, P. A., J. C. F. Padilha, and S. Guillaumin. 1996. Metabolic and endocrine changes induced by chronic heat xposure in broiler chickens: growth performance, body composition and energy retention. Br. J. Nutr. 75:195 – 204.
13. K hajali, F., and R. F. Wideman. 2010. Dietary arginine: Metabolic, environmental, immunological and physiological interrelationships. Worlds Poult. Sci. J. 66:751 – 766.
14. Kidd, M. T. 2004. Nutritional modulation of immune function in broilers. Poult. Sci. 83:650 – 657.
15. Lara, L. J., and M. H. Rostagno. 2013. Impact of heat stress on poultry production. Animals. 3:356 – 369.
16. Mahmoud, H. A., R. C. Teeter, and M. N. Makled. 1996. Arginine:lysine ratio effects on performance and carcass variables of broilers reared in thermoneutral and heat stress environments. Poult. Sci. 75:88.
17. Mendes, A. A., S. E. Watkins, J. A. England, E. A. Saleh, A. L Waldroup, and P. W. Waldroup. 1997. Influence of dietary lysine levels and arginine:lysine ratios on performance of broilers exposed to heat or cold stress during the period of three to six weeks of age. Poult. Sci. 76:472 – 478.
18. Moncada, S., and A. Higgs. 1993. The L-arginine-nitric oxide pathway. N. Engl. J. Med. 329:2002-2012.
19. Murrell, G. A., C. Szabo, J. A. Hannafin, D. Jang, M. M. Dolan, X. H. Deng, D. F. Murrell, and R. F. Warren. 1997.
20. Modulation of tendon healing by nitric oxide. Inflamm. Res. 46:19 – 27.
21. Rostagno, M. 2020. Effects of heat stress on the gut health of poultry. J. Anim. Sci. 98:1 – 9.
22. Sandercock, D. A., R. R. Hunter, G. R. Nute, M. A. Mitchell, and P. M. Hocking. 2001. Acute heat stress-induced alterations
23. in blood acid-base status and skeletal muscle membrane integrity in broiler chickens at two ages: Implications for meat quality. Poult. Sci. 80:418 – 425.
24. Settar, P., S. Yalcin, L. Turkmut, S. Ozkan, and A. Cahanar. 1999. Season by genotype interaction related to broiler growth rate and heat tolerance. Poult. Sci. 78:1353 – 1358.
25. Song, D. J., and A. J. King. 2015. Effects of heat stress on broiler meat quality. World’s Poult. Sci. J. 71:701 – 709.
26. Steiner, A. A., and L. G. S. Branco. 2001. Nitric oxide in the regulation of body temperature and fever. J. Therm. Biol. 26:325 – 330.
27. Wideman Jr, R. F., Kirby, Y. K., Ismail, M., Bottje, W. G., Moore, R. W. and Vardeman, R. C. 1995. Supplemental L-arginine attenuates pulmonary hypertension syndrome (ascites) in broilers. Poult. Sci. 74: 323 – 330.
28. Wu, G. 2009. Amino acids: Metabolism, functions, and nutrition. Amino Acids. 37:1 – 17.
29. Yang, L., G. Y. Tan, Y. Q. Fu, J. H. Feng, and M. H Zhang. 2010. Effects of acute heat stress and subsequent stress removal on function of hepatic mitochondrial respiration, ROS production and lipid peroxidation in broiler chickens. Comp. Biochem. Physiol. C. Toxicol. Pharmacol. 151:204 – 208.

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