Exceeding Essential Amino Acid Requirements and Improving Their Balance as a Means to Minimize Heat Stress in Broilers

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1 2003 Poultry Science Association, Inc. Exceeding Essential Amino Acid Requirements and Improving Their Balance as a Means to Minimize Heat Stress in Broilers A. J. Zarate,* E. T. Moran, Jr.,* 1,2 and D. J. Burnham *Poultry Science Department, Auburn University, Auburn, Alabama 36849; and Ajinomoto Heartland, Inc., Chicago, Illinois Primary Audience: Nutritionists, Extension Specialists, Live Production Personnel SUMMARY Response of broilers reared under summer conditions to feeds having essential amino acid (EAA) levels approximating 110% of their expected requirement was examined with both sexes. A commercial-type feeding regimen known to enable favorable performance under optimal conditions represented the control. Environmental conditions were sufficiently hot to depress performance but not cause death. Purified amino acids were supplemented to increase levels of limiting EAA and improve their overall balance without altering existing CP and ME. Live performance was not affected, but abdominal fat removed from the carcasses after processing significantly increased when the 110% level of EAA had been fed. Yield of the carcass without its abdominal fat, incidence of associated defects, and recovery of deboned breast meat were similar between the two dietary treatments. Both sexes responded similarly to the feed treatments. Improved amount and balance of effective amino acid intake likely increased the proportion of productive energy recovered from dietary ME; however, realization was as depot fat rather than as a benefit on live performance or muscle formation. Key words: broiler, carcass quality, heat stress, amino acid requirement, productive energy 2003 J. Appl. Poult. Res. 12:37 44 DESCRIPTION OF PROBLEM Broilers respond adversely to a hot environment by decreasing feed intake and rate of body weight gain while the extent of fat deposition increases. Presumably, diversion of resources used for muscle accretion together with a reduction in physical activity are major contributors to the increased deposition of fat [1]. Feed intake has been estimated to decrease about 3.6% per degree increase between 22 and 32 C while growth diminishes 1.5% [2]. One strategy for improving live performance of broilers suffering from heat stress has been to improve their access to limiting nutrients and decrease feed heat increment. Temim et al. [3] concluded from their research on broilers reared at high temperatures that the 1 Present address: Poultry Science Department, Auburn University, Auburn, AL 36849; Phone: ; FAX: To whom correspondence should be addressed: emoran@acesag.auburn.edu.

2 38 JAPR: Research Report TABLE 1. Composition of control feeds and those with essential amino acid (EAA) supplementation to approximate 110% of expected requirements for broilers under heat stress through each phase of production to49d(%asis) A Starter, 0 18 d Grower, d Finisher, d Withdrawal, d Ingredient Control EAA B Control EAA B Control EAA B Control EAA B Corn Soybean meal Poultry fat Salt Dicalcium phosphorus Limestone L-Lysine HCl DL-Methionine L-Arginine L-Threonine L-Tryptophan 0.01 Constant C to 100% Calculated analyses ME, kcal/kg 3,075 3,150 3,200 3,200 Crude protein Calcium Available phosphorus Sodium A All diets were formulated using average nutritional contents of ingredients as found in NRC [11]. B EAA being provided at 110% of expected need. C Vitamins, 0.25% (supplied/kg of diet: vitamin A, 7,500 IU; vitamin D 3, 2,500 IU; vitamin E, 8 IU; vitamin K, 2 mg; vitamin B 12, 0.02 mg; riboflavin, 5.5 mg; niacin, 37 mg; D-pantothenic acid, 13 mg; choline, 500 mg; folic acid, 0.5 mg; vitamin B 6, 2.2 mg; thiamine, 1 mg; biotin, 0.1 mg). Minerals, 0.25 (mg supplied/kg of diet: Mn, 66; Zn, 55; Fe, 6; Cu, 6; I, 1; Se, 0.15), Coccidiostat, 0.05% (Bio-Cox 60 Salinomycin sodium; Roche Vitamins, Inc., Parsippany, New Jersey). decrease in growth and protein intake results from inadequate protein for muscle deposition. They concluded that an increase in dietary protein may improve growth of birds reared in heat stress environments. Alleman et al. [4] found that reducing dietary protein in broilers suffering from heat always resulted in an increase of body fat and feed conversion while the percentage of breast muscle decreased. Byproduct heat from the catabolism of amino acids in excess of need of broilers has been the rationale for avoiding high-protein feeds to compensate for reduced intake [5]; however, formation of uric acid is minimal in this respect compared to that expended during protein synthesis per se [6]. Supplementing free EAA in a manner to approach an ideal balance beyond the requirement could increase effective protein and compensate for reduced feed intake without altering the level of total CP and potential heat generation. The objective of the present experiment was to increase dietary EAA levels to 110% of the approximate requirement in a common feeding regimen for broilers reared under summer conditions and to compare responses to those receiving the 100% level at the same CP and ME. MATERIALS AND METHODS Broilers originating from a Ross male Avian 24K female breeder flock were sex-separated and randomly distributed into a total of 32 floor pens (45 ft 2 /pen, 16 pens/sex, 25 chicks/pen). Chicks were placed on fresh pine shavings in an open-sided house having continuous lighting with thermostatically controlled curtains and cross-ventilation. Pens were equipped with one tube feeder and one belltype drinker, which provided access to feed and water ad libitum. Birds were vaccinated for Marek s disease, Newcastle disease, and

3 ZARATE ET AL.: ESSENTIAL AMINO ACIDS AND HEAT STRESS 39 TABLE 2. Calculated and determined amino acid composition of control feeds and essential amino acid (EAA) treatment diets for broilers grown under heat stress through each phase of production to 49 d (% as is) A Starter, 0 18 d Grower, d Finisher, d Withdrawal, d Control EAA B Control EAA B Control EAA B Control EAA B Amino acid CAL C DET D CAL DET CAL DET CAL DET CAL DET CAL DET CAL DET CAL DET Alanine Arginine Aspartic acid Cystine Glutamic acid Glycine Histidine Isoleucine Leucine Lysine Methionine Methionine + Cystine Phenylalanine Proline Serine Threonine Tryptophan Tyrosine Valine A All diets were formulated using average nutritional contents of ingredients as found in NRC [11]. B EAA = lysine, TSAA, arginine, threonine, and tryptophan being provided at 110% of expected needs. C CAL = calculated. D DET = values of duplicate analyses as determined by Ajinomoto Heartland, Inc., Chicago, IL.

4 40 JAPR: Research Report TABLE 3. The effect of increasing the levels of essential amino acids (EAA) to approximate 110% of expected requirement on live performance of broilers grown under heat stress through each phase of production to 49 d of age A EAA (%) SEX Final BW (g) Gain (g) F/G B Mortality E (%) Days 0 18 (28 ± 3 C; 54 ± 16% RH) D 100 Male Female SEM EAA NS NS NS * Sex * * NS NS Days (26 ± 3 C; 77 ± 14% RH) 100 Male 1, , Female 1, , SEM Sex *** *** *** NS Days (28 ± 4 C; 62 ± 16% RH) 100 Male 2, , Female 1, , SEM Sex *** *** *** * Days (28 ± 3 C; 72 ± 17% RH) 100 Male 2, , Female 2, , SEM Sex *** *** ** NS A Values represent the least-square means of eight replicate pens each with 25 chicks at the start of experimentation (average starting weight was 44 g). B Feed conversion corrected for mortality. C Mortality percentages were transformed to arcsine % for ANOVA, whereas SEM values were approximated from as-is percentages. D The temperature and relative humidity are given as the daily average ± standard deviation for the respective intervals. NS P > 0.10; *P < 0.05; **P < 0.01; ***P <

5 ZARATE ET AL.: ESSENTIAL AMINO ACIDS AND HEAT STRESS 41 TABLE 4. Total live performance through 49 days for broilers grown under heat stress in response to increasing levels of essential amino acids (EAA) to approximately 110% of expected requirements A Treatments 0 49 Days of age Mortality B (%) EAA (%) Sex Gain (g) F/G C Total SDS 100 Male 2, , Female 2, , SEM Sex *** *** * *** A Values correspond to the least-square means of eight replicate pens each with 25 chicks at the start of experimentation. B Percentage mortality in total and attributable to sudden death syndrome (SDS). Neither ascites nor leg problems were observed. Percentages were transformed to arcsine % for ANOVA, whereas SEM values were approximated from as-is percentages. C Feed conversion corrected for mortality. NS P > 0.10; *P < 0.05; *P < 0.01; ***P < infectious bronchitis at the hatchery then were immunized for infectious bursal disease 14 d later. An average commercial feeding regimen according to Agri Stats, Inc. [7] represented the control. Lysine, methionine, arginine, threonine, and tryptophan were added to approximate 110% of expected needs as defined by the control, whereas dietary adjustments maintained CP content (Table 1). All diets were steam pelleted, and only the feeds presented the first 18 d were offered as crumbles. Representative samples of all feeds were commercially analyzed for amino acid contents (Table 2). Experimentation was initiated in late spring and completed after 49 d in early summer. Protocols conformed to the Guide for Care and Use of Agricultural Animals in Research and Teaching [8] as monitored by the Auburn University Animal Care Committee. Birds in distress were killed by cervical dislocation. All mortality was gross necropsied, and each one was categorized as sudden death syndrome (SDS), ascites (ASC), leg problems (LEG), or other reasons. Feed conversion was corrected for mortality on a bird-day basis. Birds were held in coops approximately 14 h after the final live weighing until processing. Online processing [9] was automated and requiring a total of 16 min (9-min kill-line fol- TABLE 5. Carcass yield and abdominal fat of 49-d-old broilers grown under heat stress in response to increasing levels of essential amino acids (EAA) to approximate 110% of expected requirements A Treatments Abdominal fat B Carcass without abdominal fat C EAA (%) Sex Weight (g) Carcass (%) Weight (g) Live (%) 100 Male , , Female , , SEM EAA *** *** NS NS Sex NS *** *** ** A Values represent the least-square means of eight replicate pens with each pen providing approximately 20 carcasses. B Fat removed from the body cavity after processing expressed on an absolute basis and relative to the chilled carcass. C Carcass without neck and giblets after 4 h of slush-ice chilling and removal of abdominal fat expressed on an absolute basis and relative to the full-fed live bird. NS P > 0.10; *P < 0.05; ***P <

6 42 JAPR: Research Report lowed by a 7-min evisceration line). Warm carcasses were static slush-ice chilled for 4 h, then abdominal fat was removed, and quality defects were itemized by type and location. Carcass representatives from each pen were reduced by one-half on the basis of odd-numbered wing bands. These carcasses had the front removed for deboning the following day using stationary cones and commercial personnel following conventional procedures to obtain fillets (pectoralis major) and tenders (pectoralis minor). All data were statistically evaluated by analysis of variance involving a 2 2 factorial arrangement of the main factors (EAA level = control versus 110% of expected requirements, and sex = males versus females) in a randomized complete block design. Significant differences between means were separated by the general linear models procedure of SAS software [10]. Statistical significance was considered P < Mortality and defect percentages were transformed to arcsin % for analysis. RESULTS AND DISCUSSION The control represented typical industry practices that would support favorable live performance in an optimal environment and supplied EAA in excess of NRC [10] recommendations (Table 2). An additional 10% of EAA above requirements as defined by the average levels used by industry [7] was intended to enhance their overall balance and intake while perpetuating the same CP essentially increased support for growth by displacing non-eaa and those EAA already in excess. The average environmental temperature and humidity were moderately oppressive and did not appear to cause distress to the flock until labored panting became obvious midway through experimentation (Table 3). Regardless, the feeds having increased dietary EAA did not improve body weight gain or feed conversion through any part of the 49 d of experimentation or in total (Table 4). Added EAA reduced chick mortality through the first 18 d, but this advantage was not apparent thereafter or in total. Throughout experimentation, males had advantages in body weight and feed conversion compared to females; however, the converse was TABLE 6. Defects associated with the chilled carcass of 49-d-old broilers grown under heat stress in response to increasing levels of essential amino acids (EAA) to approximate 110% of expected requirements (%) A Treatments Wings Back-thigh Broken Breast Skin Skin Grade EAA (%) Sex Dislocation bones Bruising Drum bruise (broken clavicle) Bruising tear scratch A 100 Male Female SEM NS NS NS NS NS Sex NS NS NS NS NS NS *** * NS NS NS NS NS NS A Values are the averages of eight replicate pens each providing approximately 20 carcasses. NS P > 0.10; *P < 0.05; **P < 0.01.

7 ZARATE ET AL.: ESSENTIAL AMINO ACIDS AND HEAT STRESS 43 TABLE 7. Yield of breast meats from carcasses of 49-d-old broilers grown under heat stress in response to increasing levels of essential amino acids (EAA) to approximate 110% of their expected requirements A Treatments Breast fillet Tenders EAA (%) Sex Weight (g) Carcass (%) Weight (g) Carcass (%) 100 Male Female SEM Sex *** NS *** *** Interaction NS NS * NS A Values represent the least-square means of birds from eight replicate pens with each pen providing approximately 20 carcasses for deboning. NS P > 0.10; *P < 0.05; ***P < true for mortality, whereas their responses to the feed treatments were similar. Changes in body composition in terms relevant to the broiler industry were measured subsequent to processing. The amount of depot fat removed from the abdominal cavity after carcass chilling was significantly increased with broilers that had received added EAA (Table 5); however, carcass yield after fat removal, incidence of associated quality defects (Table 6), and amounts of skinless boneless meats deboned from the breast (Table 7) were all similar to the control. Again, both sexes responded similarly to the feed treatments. Overall results suggest that increasing EAA associated with constant CP improved their balance as well as productive energy realized from the feed, but this improvement was as fat not muscle. Protein formation generates extensive heat production [6], which appears to be limited by a bird s ability to cope with an adverse environment. Fat deposition is associated with minimal heat and is enhanced by increasing temperatures. Apparently, the productive advantage from feed EAA improvements under the present terms of experimentation did not relieve heat formation to the extent that muscle formation could benefit. CONCLUSIONS AND APPLICATIONS 1. Increasing the percentage of EAA and the balance within dietary CP can improve the proportion of productive energy recovered from ME. 2. Heat increment experienced by broilers receiving EAA enhanced CP appeared to be minimal, and any associated advantage in productive energy translated more into fat deposition than meat. REFERENCES AND NOTES 1. Geraert, P. A., J. C. F. Padilha, and S. Guillaumin Metabolic and endocrine changes induced by chronic heat exposure in broiler chickens: Biological and endocrinological variables. Br. J. Nutr. 75: Baziz, H. A., P. A. Geraert, J. C. F. Padilha, and S. Guillaumin Chronic heat exposure enhances fat deposition and modifies muscle and fat partition in broiler carcasses. Poult. Sci. 75: Temim, S. A. M. Chagneau, R. Peresson, and S. Tesseraud Chronic heat exposure alters protein turnover of three differ- ent skeletal muscles in finishing broiler chickens fed 20 or 25% protein diets. J. Nutr. 130: Alleman, F., J. Michel, A. M. Chagneau, and B. Leclercq The effects of dietary protein independent of essential amino acids on growth and body composition in genetically lean and fat chickens. Br. Poult. Sci. 41: Temim, S., A. M. Chagneau, S. Guillaumin, J. Michel, R. Peresson, and S. Tesseraud Does excess dietary protein improve growth performance and carcass characteristics in heatexposed chickens? Poult. Sci. 79:

8 44 JAPR: Research Report 6. Macleod, M. G Effects of amino acid balance and energy: protein ratio on energy and nitrogen metabolism in male broiler chickens. Br. Poult. Sci. 38: Agri Stats, Inc., Fort Wayne, IN. 8. Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching Federation of Animal Science Societies, Savoy, IL. 9. Kill line required 9 min, followed by manual transfer to the evisceration line, which required 7 min to chilling. Processing conditions were stunning at 50 V DC, 25 mamp and 100 hz, scalding at 57 C (Centrell Machine Co., Gainesville, GA), plucking (Model JM-32 C-M, Meyn USA, Inc., Gainesville, GA), and automated evisceration (Mark IV Pritchard Systemate, Atlanta, GA). 10. SAS Institute SAS/STAT User s Guide. Release 6.03 Edition. SAS Institute Inc., Cary, NC. 11. National Research Council Nutrient Requirements of Domestic Animals. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Sci., Washington, DC.