Dietary potassium and available phosphorous on broiler growth performance, carcass characteristics, and wooden breast

Dietary potassium and available phosphorous on broiler growth performance, carcass characteristics, and wooden breast

∗

Prestage Department of Poultry Science, NC State University, Raleigh, NC 27695-7608; and † Department of Population and Health Pathobiology, College of Veterinary Medicine, NC State University, Raleigh, NC 27607 finisher diets, respectively. Blood physiology was measured at 29 and 42 d. Carcass data, wooden breast and white striping scores were measured at 35 and 43 d. The K+ diets improved feed conversion ratio at 35 d (1.52 vs 1.57 g: g), reduced body weight at 42 d (3524 vs 3584 g), reduced hemoglobin (6.83 vs 7.58 g/dL), and packed cell volume (20.1 vs 22.3%) at 29 d, reduced ionized blood calcium (1.42 vs 1.47 mmol/L) at 42 d, and reduced partial pressure of blood CO2 (49.1 vs 54.7 mm/Hg) at 42 d relative to broilers fed basal K- diets (P < 0.05). Fixed AvP diets improved feed conversion ratio at 28 and 42 d, increased percentage breast meat (28.85 vs 27.58%) and carcass water pickup (2.72 vs 1.42%) at 35 d, and reduced wooden breast (2.88 vs 3.69) at 43 d (P < 0.05).

ABSTRACT Broiler dietary potassium (K) and available phosphorous (AvP) have decreased in recent years but both ions are intimately involved in the elimination of hydrogen ions that are produced during rapid growth. It was hypothesized that the decrease of these dietary electrolytes was related to the development of myopathies, and thus increased dietary K and/or AvP would reduce the occurrence of breast myopathies. A total of 320 Ross male broiler chicks were placed into 16 pens and fed 2 diet series containing either decreasing AvP levels of 0.45, 0.40, and 0.35% in the starter, grower, and finisher diets, respectively (Decline), or a fixed AvP of 0.45% in all dietary phases (Fixed). To complete a 2 × 2 design either normal basal dietary K (K-) (0.86, 0.77, 0.68%) or added dietary K (K+) (1.01, 0.93, 0.88%) were also applied to starter, grower, and

Key words: wooden breast, broilers, electrolytes, myopathies 2019 Poultry Science 0:1–10 http://dx.doi.org/10.3382/ps/pez015

INTRODUCTION

sue infiltration (Kuttappan et al., 2013; Sihvo et al., 2014; Petracci et al., 2015). Moreover, consumers have demonstrated a tendency to avoid these products when presented with a choice (Kuttappan et al., 2012). The optimum relationship between sodium (Na), potassium (K), and chloride (Cl) has been described by dietary electrolyte balance (DEB) as being essential for proper acid-base balance (Mongin and Sauveur, 1977; Mongin, 1981). The DEB has been calculated in its short form as Na + K—Cl (Mongin and Sauveur, 1977; Mongin, 1981). Besides playing roles in DEB and acid-base balance, K has been reported to be intimately involved in osmotic regulation, muscle cell membrane potential (voltage gradient), and glucose movement and absorption (Rinehart and Rogler, 1967; Oliveira et al., 2005). While the NRC (1994) indicated that soybean meal contained 2.00% K, recent literature reported levels of K as low as 0.90% in some Brazilian sources (Borges et al., 2004). While the NRC (1994) suggested the minimum requirement for K was only 0.30%, more recent literature has indicated that K requirements may be much greater (Borges et al., 2004; Oliveira et al., 2005) at levels 2 to 3 times that suggested by the NRC to achieve improved body weight (BW) and feed conversion ratio (FCR).

As the world demand for poultry increased a larger and greater breast yield broiler became more economical to grow and process (Brewer et al., 2012). Wooden breast (WB) and white striping (WS) muscle myopathies have concurrently become a quality concern as well as a potential food safety concern due to the inflammatory tissue associated with WB (United States Department of Agriculture, 2017). The WB and WS myopathies have been associated with fast growing high yield lines of broiler chickens (Kuttappan et al., 2012; Petracci et al., 2015; Trocino et al., 2015). Both myopathies have demonstrated considerable reduction in muscle protein functionality (Petracci et al., 2013; Mudalal et al., 2014) and a decrease in overall protein content (Petracci et al., 2013), which has contributed to a reduced ability to absorb marinade and maintain juiciness through the cooking process (Mudalal et al., 2014). Both myopathies have been characterized by an onset of myodegeneration, necrosis, and connective tis C 2019 Poultry Science Association Inc. Received July 17, 2018. Accepted January 15, 2019. 1 Corresponding author: [email protected]

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M. L. Livingston,∗,1 C. D. Landon,† H. J. Barnes,† J. Brake,∗ and K. A. Livingston∗

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LIVINGSTON ET AL.

MATERIALS AND METHODS Facilities and Rearing This trial was conducted between the months of September and October 2015. All procedures used in this study were reviewed and approved by the Institutional Animal Care and Use Committee. Eggs were collected from 42-wk-old Ross YPM males crossed with Ross 708 females and stored for no more than 7 d at 15◦ C. Incubation began with an initial preheating of trayed eggs at room temperature (26.0◦ C) for 12 h with portable fans for air movement. Eggs were then moved into an incubator (Jamesway Incubator Company, Model 252B, Ft. Atkinson, WI) and held through E3 at 38.0◦ C dry bulb temperature and 29.4◦ C wet bulb temperature. Machine dry bulb set point temperature was changed to 37.5◦ C and wet bulb to 28.3◦ C on E4 of incubation while ventilation was gradually increased as incubation progressed. Dry bulb temperature was gradually decreased after E12 of incubation to maintain an internal egg temperature of approximately 37.8◦ C. Hatched chicks were sex-sorted and a total of 320 male broiler chicks were individually neck tagged and placed in 16 uniform pens (1.2 m x 4.0 m; 4.8 m2 ) with 20 chicks per pen (blocked by location within the house). Each pen was supplied with one bell water drinker, two tube feeders, and bedded with fresh pine shavings (15 cm deep).

Feed Management Broilers were assigned to one of 4 corn-soy based dietary treatments, containing either existing basal levels of K (K-; 0.86%, 0.77%, 0.68%) or increased levels of K (K+; 1.01%, 0.93%, 0.88%) in a starter, grower, finisher three-phase dietary program, respectively. These variances in K level were used to create a 40 to 50 meq/kg deviation in DEB. Diets were also formulated with decreasing levels of AvP (Decline; 0.45, 0.40, 0.35%) or fixed levels of AvP (Fixed; 0.45, 0.45, 0.45%) in the same starter, grower, finisher 3-phase dietary program, respectively. This created a 2 × 2 factorial design of K

(K- vs K+) and declining or fixed levels of AvP in sequential starter, grower, and finisher diets (Decline vs Fixed). There were 4 treatments and 16 total pens, with 4 replications per treatment (20 birds in each pen). Diets were manufactured from common basal diets to insure uniform intake of all dietary nutrients except those of interest at the expense of inert fillers such as sand and/or vermiculite (Table 1). Potassium and phosphorous was analyzed using Inductively Coupled PlasmaAtomic Emission Spectrometry (ICP-AES) by a third party laboratory (Waters Agricultural Laboratory, Inc; Warsaw, NC).

Live Performance and Blood Physiology Broiler BW and feed consumption were recorded at 1, 16, 21, 28, 35, and 42 d of age. At 29 and 42 d of age two broilers per pen were selected for venous blood analysis. Broilers were selected based on their BW being within one standard deviation above the pen average due to previous data suggesting that greater BW was correlated with greater frequency of myopathies. Approximately 2 mL of blood was drawn from the left branchial R vein and analyzed using the i-Stat handheld blood analyzer fitted with a CG8+ cartridge (Abbott Point of Care Inc., Princeton, NJ), which measured packed cell volume, hemoglobin, ionized calcium, glucose, Na, K, pH, partial pressure of carbon dioxide (pCO2 ), bicarbonate, total carbon dioxide, base excess in the extracellular fluid, partial pressure of oxygen (pO2 ), and oxygen saturation of hemoglobin (sO2 ). A systematic approach to catching broilers, drawing of blood, analysis, and re-introduction to the pen was utilized to assure uniform collection of blood and handling of broilers.

Processing Broilers were selected at 35 and 43 d, based on BW within one standard deviation above mean experiment wide BW, and processed in a commercial processing line while maintaining individual and treatment identity throughout the process. The 43 d broilers processed were the same broilers used during the 42 d blood sampling. Broilers were given full access to water during their 4 h lairage time prior to processing. Identified broilers were then collected and transported to the pilot processing facility located at the site followed by shackling and stunning in a salt saturated saline head stun cabinet. Broilers were exsanguinated for 120 s by opening of the jugular vein and carotid artery with a single knife cut by a trained individual followed by scalding in hot water for 120 s at 60◦ C. This was followed by feather picking for 30 s (Meyn Food Processing Technology B.V., Westeinde Amsterdam, The Netherlands). Head and feet were removed, vent opened (VC Poultry Vent Cutter, Jarvis Product Corp., Middleton, CT, USA), and viscera and giblets removed manually and discarded. Hot carcass weight was recorded followed by

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Efforts to decrease dietary phosphorus have been implemented in order to reduce the environmental impact of the poultry industry (Maguire et al., 2005; Leytem et al., 2007). The importance of dietary phosphorus in acid-base balance has been demonstrated to be through its effects in the kidney (Mizgala and Quamme, 1985; Hamm and Simon, 1987; Leytem et al., 2008). The potential exists for an acid-base disturbance to present itself in the muscle mass of fast-growing high breast yield broilers due to reduced dietary levels of K and/or available phosphorous (AvP). This study evaluated increased dietary concentration of K and AvP and their effects on live performance, breast muscle characteristics and myopathies, and the blood physiology of fastgrowing broilers.

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DIET AND BREAST MYOPATHIES Table 1. Composition of experimental basal starter, grower, and finisher diets. Starter5

Grower6

Finisher7

Decline Ingredients

K-

K+

K-

Fixed K+

K-

Decline K+

K-

Fixed K+

K-

K+

———————————————————————(%)———————————————————————– 56.90 56.90 63.98 63.98 63.98 63.98 65.48 65.48 65.48 65.48 32.06 32.06 23.74 23.74 23.74 23.74 21.35 21.35 21.35 21.35 5.00 5.00 5.96 5.96 5.96 5.96 5.22 5.22 5.22 5.22 2.00 2.00 2.43 2.43 2.43 2.43 3.99 3.99 3.99 3.99 1.34 1.34 0.84 0.84 1.16 1.16 0.67 0.67 1.30 1.30 0.61 0.61 0.74 0.74 0.82 0.82 0.66 0.66 0.82 0.82 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.00 0.30 0.00 0.34 0.00 0.34 0.00 0.42 0.00 0.42 0.40 0.10 0.40 0.06 0.40 0.06 0.40 0.00 0.40 0.00 0.20 0.20 0.40 0.40 0.08 0.08 0.80 0.80 0.00 0.00 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.23 0.23 0.17 0.17 0.17 0.17 0.11 0.11 0.11 0.11 0.14 0.14 0.20 0.20 0.20 0.20 0.13 0.13 0.13 0.13 0.11 0.11 0.09 0.09 0.09 0.09 0.14 0.14 0.14 0.14 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 100 100 100 100 100 100 100 100 100 100

Calculated nutrient content Crude protein Calcium Available phosphorus Potassium Total lysine Total methionine Total threonine Total methionine + cysteine Sodium Metabolizable energy (kcal/g)

23.00 0.83 0.45 0.86 1.31 0.59 0.88 0.95 0.22 2.93

23.00 0.83 0.45 1.01 1.31 0.59 0.88 0.95 0.22 2.93

20.00 0.80 0.40 0.77 1.05 0.49 0.76 0.81 0.22 3.05

20.00 0.80 0.40 0.93 1.05 0.49 0.76 0.81 0.22 3.05

20.00 0.90 0.45 0.77 1.05 0.49 0.76 0.81 0.22 3.05

20.00 0.90 0.45 0.93 1.05 0.49 0.76 0.81 0.22 3.05

18.50 0.70 0.35 0.68 1.00 0.42 0.76 0.72 0.22 3.15

18.50 0.70 0.35 0.88 1.00 0.42 0.76 0.72 0.22 3.15

18.50 0.90 0.45 0.68 1.00 0.42 0.76 0.72 0.22 3.15

18.50 0.90 0.45 0.88 1.00 0.42 0.76 0.72 0.22 3.15

Analyzednutrient content Crude protein Crude fat Calcium Phosphorus Potassium

22.41 4.48 0.74 0.69 0.71

22.65 2.82 0.77 0.65 0.82

19.46 4.24 0.71 0.59 0.60

21.75 4.66 0.66 0.58 0.72

21.12 5.14 0.96 0.75 0.68

21.25 4.08 0.89 0.71 0.75

19.37 6.01 0.74 0.55 0.57

19.05 5.60 0.66 0.61 0.77

18.09 6.08 0.85 0.57 0.59

19.72 6.94 0.91 0.58 0.77

316 278

355 306

293 249

334 280

293 270

334 288

270 242

321 293

270 247

321 293

Calculated DEB8 (meq/kg) Actual DEB9 (meq/kg) 1

Vitamin premix supplied the following per kg of diet: 13 200 IU vitamin A, 4000 IU vitamin D3 , 33 IU vitamin E, 0.02 mg vitamin B12 , 0.13 mg biotin, 2 mg menadione (K3 ), 2 mg thiamine, 6.6 mg riboflavin, 11 mg d-pantothenic acid, 4 mg vitamin B6 , 55 mg niacin, and 1.1 mg folic acid. 2 Mineral premix supplied the following per kg of diet: manganese, 120 mg; zinc, 120 mg; iron, 80 mg; copper, 10 mg; iodine, 2.5 mg; and cobalt, 1 mg. 3 Selenium premix provided 0.2 mg Se (as Na2 SeO3 ) per kg of diet. 4 Coccidiostat supplied monensin sodium at 90 mg/kg of food. 5 Starter diet was fed to approximately 16 d of age, 910 g per bird. 6 Grower diet was fed from approximately 17 to 35 d of age, 2750 g per bird. 7 Finisher diet was fed from approximately 36 to end of experiment. 8 Dietary electrolyte balance calculated using matrix values of chloride, sodium, and potassium. 9 Dietary electrolyte balance calculated using matrix values of chloride and sodium, and analyzed values of potassium.

the carcass being chilled in an ice-water bath for 4 h before water was drained. Carcasses were allowed to lay in drained ice for approximately 18 h prior to cut-up. Carcass parts including fat pad, wings, thighs, drums, boneless skinless breasts (Pectoralis major), tenders (Pectoralis minor), and remaining frame were separated and individually weighed. A WB and WS scoring system was developed for the Pectoralis major using a one to four-point ordinal scale of measurement executed by a single trained and experienced technician. The WB scoring system comprised a hand palpation

method where a score of 1 indicated normal or no signs of WB. A score of 2 indicated some firming or hardening of the breast with over 50% of non-affected tissue being pliable. A WB score of 3 indicated that more than 50% of the breast was hard and resisted palpation but with some pliability still present. A WB of 4 indicated no presence of pliability and over 90% of the breast hard to the touch. The WS scoring system was similar with a score of 1 for normal breast tissue or no signs of striping. A WS score of 2 indicated a mild amount of visible striations, a WS score of 3 indicated a moderate

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Corn Soybean meal (48% CP) Poultry by-product meal Poultry fat Dicalcium phosphate (18.5% P) Limestone Salt Potassium carbonate Vermiculite filler Sand Choline chloride (60%) Vitamin premix1 Mineral premix2 Selenium premix3 DL-Methionine L-Lysine L-Threonine Coccidiostat4 Total

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LIVINGSTON ET AL.

Statistical Analysis Dependent variables (live performance data, carcass data, blood physiology) were analyzed as a 2 × 2 factorial design with independent variables of K- versus K+ and dietary phase AvP (Fixed, Decline). Data was analyzed using the Proc GLM Procedure of SAS (SAS Institute, 2009). Live performance and carcass data were analyzed using pen as the investigational unit while each broiler was considered an investigational unit for blood gas and carcass characteristics. Percentage data were arsine transformed where necessary. Means were separated with Tukey’s adjustment for multiple comparisons test (P < 0.05). Further analysis of data was performed using WS and WB scores as independent variables (regardless of treatment group) with similar dependent variables as above and the GLM procedure of SAS while correlation coefficients were determined using the Proc Corr procedure of SAS (SAS Institute, 2009). Significance was determined at P < 0.05 or P < 0.01 while trends were noted at P < 0.10.

RESULTS Live Performance The effects of dietary K and AvP on feed consumption, BW, and FCR are shown in Tables 2, 3, and 4, respectively. Feed consumption between 29 to 35 d was reduced in broilers fed Fixed AvP (P < 0.05), while cumulative feed intake (1 to 42 d) of K+ fed broilers was reduced by over 120 g (P = 0.05). There were no significant interactions in broiler feed consumption. No differences in broiler BW were observed until 42 d of age when broilers fed added K (K+) exhibited an approximately 60 g reduced BW (P < 0.05). There were no significant interactions in broiler BW. Broiler FCR was similar among treatment groups from 0 to 21 d of age. Broilers fed Fixed AvP diets exhibited improved cumulative FCR to 42 d of age (P < 0.05) as well as from 22 to 28 d of age (P < 0.01). Broilers fed supplemental K+ diets trended toward an improved FCR from 29 to 35 d (P < 0.10) when compared to broilers fed basal K- diets. Cumulatively to 42 d, the diet containing basal K and decreased AvP (K-/Decline) exhibited poorer FCR (P < 0.05) related to the 3 other combinations (Table 4).

Blood Physiology The effects of dietary K and AvP on broiler blood physiology at 29 and 42 d are shown in Tables 5 and 6, respectively. At 29 d broilers fed K+ diets exhibited a reduced (P < 0.01) packed cell volume and hemoglobin

Table 2. Effect of dietary potassium (K) and dietary phase levels of available phosphorus (AvP) on weekly feed consumption (g: broiler). Feed consumption1 Available phosphorus3

Potassium2 KK+

Decline Fixed SEM4 K-/Decline K+/Decline K-/Fixed K+/Fixed SEM4

1 to 16 d

17 to 21 d

22 to 28 d

29 to 35 d

36 to 42 d

Total

———————————————————(g/broiler)——————————————————– 784 590 883 1463y 1623 5346a 774 572 854 1441x 1580 5224b 780 579 863 1469a 1620 5311 1583 5258 780 583 874 1437b 5

9

14

9

22

40

783 776 786 773

593 564 586 580

887 840 880 868

1486 1452 1442 1431

1643 1597 1604 1564

5393 5230 5299 5217

8

12

19

12

32

56

(Probability > F) K AvP KxAvP

0.21 0.97 0.74

0.17 0.72 0.39

0.14 0.58 0.38

0.09 0.02 0.34

Means within a column lacking a common superscript differ significantly (P < 0.05). Means within a column lacking a common superscript differ significantly (P < 0.10). 1 Main effect means calculated using period pen feed consumption ÷ number of broilers per pen. 2 (K-) basal levels of K; (K+) 0.30, 0.34, 0.42% potassium carbonate (starter, grower, finisher). 3 (Decline) 0.45%, 0.40%, 0.35% AvP (starter, grower, and finisher); (Fixed) 0.45% AvP (starter, grower, and finisher). 4 SEM = Standard error of mean. a,b x,y

0.20 0.26 0.92

0.05 0.36 0.48

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amount of striping, and a WS score of 4 indicated severe striations across the ventral portion of the boneless skinless breast fillet. At 24 h postmortem the Pectoralis major was evaluated for WS and WB as well as final meat pH using an Oakton (phmtr30) pH meter fitted with a spear probe calibrated with pH 4 and 7 buffers. Drip loss was calculated by then hanging the Pectoralis major for 48 h in a 3◦ C cooler and recording the final weight relative to the 24 h post mortem weight.

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DIET AND BREAST MYOPATHIES Table 3. Effect of dietary potassium (K) and dietary phase levels of available phosphorus (AvP) on weekly body weight. Body weight1 Available phosphorus3

Potassium2

16 d

21 d

28 d

35 d

42 d

Decline Fixed

691 699

1136 1143

1685 1709

2628 2650

3540 3568

4

6

12

9

14

690 693 705 693

1135 1138 1153 1133

1695 1675 1723 1695

2630 2625 2658 2643

3570 3510 3598 3538

9

11

25

19

24

SEM4 K-/Decline K+/Decline K-/Fixed K+/Fixed SEM4

(Probability > F) K AvP KxAvP

0.59 0.42 0.42

0.46 0.60 0.35

0.35 0.35 0.88

0.62 0.28 0.81

0.03 0.28 1.00

Means within a column lacking a common superscript differ significantly (P < 0.05). Main effect means calculated using mean BW of 8 pens to 42 d. 2 (K-) basal levels of K; (K+) 0.30, 0.34, 0.42% potassium carbonate (starter, grower, finisher). 3 (Decline) 0.45%, 0.40%, 0.35% AvP (starter, grower, and finisher); (Fixed) 0.45% AvP (starter, grower, and finisher). 4 SEM = Standard error of mean. a,b 1

Table 4. Effect of dietary potassium (K) and dietary phase levels of available phosphorus (AvP) on feed conversion ratio (FCR). FCR for period (d—d)1 Available phosphorus3

Potassium2

0–16

17–21

22–28

29–35

36–42

1–42

———————————————————(g:g)——————————————————— 1.20 1.34 1.53 1.57y 1.77 1.49 1.19 1.29 1.53 1.52x 1.81 1.48

KK+

1.20 1.19

1.30 1.33

1.55A 1.51B

1.56 1.53

1.81 1.78

1.50a 1.48b

SEM4

0.01

0.01

0.01

0.01

0.01

0.01

K-/Decline K+/Decline K-/Fixed K+/Fixed

1.21 1.19 1.19 1.20

1.34 1.27 1.33 1.32

1.54 1.55 1.51 1.51

1.59 1.53 1.55 1.52

1.78 1.84 1.77 1.78

1.52a 1.48b 1.47b 1.48b

SEM4

0.01

0.03

0.02

0.03

0.05

0.01

0.52 0.37 0.51

0.21 0.04 0.04

Decline Fixed

(Probability > F) K AvP K x AvP

0.59 0.29 0.24

0.18 0.42 0.39

0.65 < 0.01 0.65

0.07 0.28 0.43

Means within a column lacking a common superscript differ significantly (P < 0.05). Means within a column lacking a common superscript differ significantly (P < 0.01). 1 Main effect means calculated using FCR from 8 pens. FCR = weekly BW gain ÷ weekly feed consumption, interaction effect means calculated using FCR from 4 pens. 2 (K-) basal levels of K; (K+) 0.30, 0.34, 0.42% potassium carbonate (starter, grower, finisher). 3 (Decline) 0.45%, 0.40%, 0.35% AvP (starter, grower, and finisher); (Fixed) 0.45% AvP (starter, grower, and finisher). 4 SEM = Standard error of mean. a,b

A,B

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————————————————————(g)—————————————————– 698 1144 1709 2644 3584a 693 1135 1685 2634 3524b

KK+

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LIVINGSTON ET AL.

Table 5. Effect of dietary potassium (K) and dietary phase levels of available phosphorus (AvP) on broiler blood pH, sodium (Na), potassium (K), hemoglobin (Hgb), packed cell volume (PCV), glucose (Glu), ionized calcium (iCa), saturated oxygen (S O2 ), partial pressure of oxygen (P O2 ), partial pressure of carbon dioxide (P CO2 ), total carbon dioxide (T CO2 ), bicarbonate (HCO3 ), base excess in the extra cellular fluid (BEecf) at 29 d of age. Available phosphorus1,3

Potassium1,2

Decline Fixed

Hgb

PCV

—–(mmol/L)—– 7.37 143.13 5.64 7.39 142.94 5.73

(g/dL) 7.58A 6.83B

(%) 22.25A 20.06B

—(mg/dL)— 255.06 1.45 259.00 1.46

(%) 68.63 68.38

—(mmHg)— 38.44 50.00 37.00 47.51

——–(mmol/L)——– 30.19 28.76 3.38 30.00 28.63 3.50

143.81y 142.25x

5.66 5.71

7.22 7.19

21.19 21.13

254.88 259.19

67.81 69.19

37.06 38.38

48.73 48.78

30.06 30.13

28.63 28.75

3.44 3.44

2.56 0.01 1.76 (Probability > F)

0.98

1.14

0.42

0.39

0.47

0.48 0.52 0.83

0.30 0.99 0.98

0.83 0.94 0.52

0.87 0.89 0.55

0.90 1.00 0.61

7.38 7.38

Na

K

SEM4

0.01

0.41

0.08

0.13

0.39

K P KxAvP

0.42 0.99 0.75

0.82 0.07 0.82

0.54 0.78 0.21

< 0.01 0.89 0.41

< 0.01 0.93 0.42

Glu

0.44 0.40 0.09

iCa

1.46 1.46

0.58 0.78 0.68

S O2

0.95 0.71 0.97

P O2

P CO2

T CO2

HCO3

BEecf

Means within a column lacking a common superscript differ significantly (P < 0.10). Means within a column lacking a common superscript differ significantly (P < 0.01). 1 Main effect means calculated using 16 broilers at 29 d of age. 2 (K-) basal levels of K; (K+) 0.30, 0.34, 0.42% potassium carbonate (starter, grower, finisher). 3 (Decline) 0.45%, 0.40%, 0.35% AvP (starter, grower, and finisher); (Fixed) 0.45% AvP (starter, grower, and finisher). 4 SEM = Standard error of mean. x,y

A,B

Table 6. Effect of dietary potassium (K) and dietary phase levels of available phosphorus (AvP) on broiler blood pH, sodium (Na), potassium (K), hemoglobin (Hgb), packed cell volume (PCV), glucose (Glu), ionized calcium (iCa), saturated oxygen (S O2 ), partial pressure of oxygen (P O2 ), partial pressure of carbon dioxide (P CO2 ), total carbon dioxide (T CO2 ), bicarbonate (HCO3 ), base excess in the extra cellular fluid (BEecf) at 42 d of age. Available phosphorus1,3

Potassium1,2 KK+

Decline Fixed

pH

Na

K

Hgb

PCV

7.33x 7.37y

—(mmol/L)— (g/dL) (%) 145.81 5.86 7.10 20.88 145.44 5.86 7.12 20.94

7.36 7.35

145.81 145.44

5.78 5.94

7.24 6.98

21.25 20.56

0.01

0.34

0.10

0.13

0.38

SEM4 K P

Glu

iCa

S O2

P O2

P CO2

T CO2

HCO3

BEecf

—(mg/dL)— (%) —–(mmHg)—– ——–(mmol/L)———– 250 1.47y 70.37 40.88 54.70a 30.38 28.84 2.88 253 1.42x 73.00 42.31 49.10b 29.31 27.99 2.75 256y 1.45 248x 1.44 2.27

0.01

70.56 72.82

40.69 42.50

50.67 53.13

29.38 30.31

27.98 28.85

2.38 3.25

1.67

1.27

1.48

0.45

0.42

0.48

0.59 0.50 0.83

0.05 0.40 0.92

0.25 0.31 0.46

0.32 0.31 0.50

0.89 0.35 0.50

(Probability > F) 0.09 0.65 0.87

0.60 0.60 1.00

0.98 0.41 0.34

0.94 0.35 0.84

0.94 0.39 0.81

0.51 0.07 0.12

0.09 0.80 0.91

0.45 0.52 0.45

KxAvP Means within a column lacking a common superscript differ (P < 0.10). Means within a column lacking a common superscript differ significantly (P < 0.05). 1 Main effect means calculated using 16 broilers at 42 d of age. 2 (K-) basal levels of K; (K+) 0.30, 0.34, 0.42% potassium carbonate (starter, grower, finisher). 3 (Decline) 0.45%, 0.40%, 0.35% AvP (starter, grower, and finisher); (Fixed) 0.45% AvP (starter, grower, and finisher). 4 SEM = Standard error of mean. x,y

a,b

when compared to broilers fed basal K- diets (Table 5). These differences did not persist to 42 d (Table 6) but K+ diets then produced broilers that exhibited reduced pCO2 (P < 0.05). Finally, added dietary K (K+) produced broilers with numerically greater blood pH (P < 0.10) at 42 d. Fixed dietary AvP numerically (P < 0.10) reduced Na at 29 d and glucose at 42 d. There were no significant interactions at either age (data not shown for brevity).

Meat Quality and Yield The effects of dietary K and AvP on broiler meat quality, yield, and myopathies at 35 and 43 d are shown in Tables 7 and 8, respectively. All broilers selected for processing were similar in BW at both 35 and 43 as planned. There were no main effect differences observed between treatment groups for carcass weight, dressing percentage, or absolute Pectoralis major weight at either age.

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KK+

pH

7

DIET AND BREAST MYOPATHIES

Table 7. Effect of dietary potassium (K) and dietary phase levels of available phosphorus (AvP) on BW, hot carcass weight (HCW), dressing percentage (Dress), carcass moisture absorption (Pick-up), Pectoralis major weight (Pec. major), Pectoralis major yield (Pec. Yield), Wooden Breast (WB) and White Striping (WS) scores, pH, and moisture loss from breast (Drip Loss) at 35 d of age. BW and carcass1

KK+ Decline Fixed SEM11 K-/Decline K+/Decline K-/Fixed K+/Fixed SEM11

BW

HCW

Dress5

Pick-up6

Pec. major

Pec. yield7

WB8

WS9

pH

Drip loss10

——–(g)—— 2791 2217 2843 2218

——–(%)——– 79.15 1.84 78.33 2.29

(g) 624 628

(%) 28.12 28.31

3.20 3.28

1.97 2.03

5.89 5.88

(%) 4.94 4.92

2811 2823

79.13 78.35

1.42b 2.72a

613 638

27.58x 28.85y

3.29 3.19

2.00 2.00

5.86 5.91

5.19 4.67

2223 2211

23

18

0.38

0.31

10

0.34

0.17

0.16

0.02

0.22

2793 2830 2790 2856

2226 2220 2208 2215

79.15 79.11 79.15 77.56

1.19 1.64 2.49 2.94

611 616 636 641

27.44 27.73 28.81 28.88

3.14 3.43 3.25 3.13

1.57b 2.43a 2.38a 1.63b

5.80a 5.93b,c 5.98c 5.83a,b

5.42 4.96 4.45 4.88

47

40

0.75

0.60

20

0.69

0.35

0.32

0.04

0.45

0.82 0.77 0.55

0.87 1.00 0.02

0.82 0.30 < 0.01

0.97 0.25 0.33

(Probability > F) K P KxAvP

0.29 0.81 0.77

0.98 0.77 0.87

0.29 0.32 0.32

0.46 0.04 1.00

0.82 0.24 1.00

0.79 0.07 0.87

Means within a column lacking a common superscript differ (P < 0.10). Means within a column lacking a common superscript differ significantly (P < 0.05). 1,2 Main effect means calculated using 16 broilers at 35 d of age. 3 (K-) basal levels of K; (K+) 0.30, 0.34, 0.42% potassium carbonate (starter, grower, finisher). 4 (Decline) 0.45%, 0.40%, 0.35% AvP (starter, grower, and finisher); (Fixed) 0.45% AvP (starter, grower, and finisher). 5 Dress = HCW ÷ BW x 100%. 6 Pick-up = (chilled carcass weight)—HCW ÷ HCW x 100%. 7 Pec. Yield = Major weight ÷ Cold Carcass weight x 100%. 8 WB = wooden breast (1 = none, 2 = mild, 3 = moderate, 4 = severe). 9 WS = white Striping (1 = none, 2 = mild, 3 = moderate, 4 = severe). 10 Drip Loss = (initial Pec. major weight—final Pec. major weight) ÷ initial weight x 100. 11 SEM = Standard error of mean. x,y

a,b

At 35 d broilers receiving Fixed levels of AvP resulted in greater moisture pick-up during carcass chilling (P < 0.05) and tended towards an improved breast muscle yield (P < 0.10) when compared to Decline AvP (Table 7) diets but these results were not observed at 43 d (Table 8). The interaction effect of AvP and K at 35 d resulted in reduced WS (P < 0.01) and lower 24 h muscle pH (P < 0.05) in broilers fed either K-/Decline or K+/Fixed diets (Table 7). The interaction effect of AvP and K (K+/Fixed) reduced breast muscle yield at 43 d, whereas either of these nutrients independently (K+/Decline or K-/Fixed) significantly improved percentage breast muscle when compared to the K+/Fixed diets with the K-/Decline diets intermediate (Table 8). Water pick-up was increased by the Fixed AvP diets at 35 d (Table 7; P < 0.05). There were no significant main effects of dietary K or AvP on WS scores at either age (Table 7 and 8). However, the 43 d WB scores of broilers fed Fixed AvP diets was reduced (P < 0.05) when compared to Decline birds (Table 8). Frequency distribution, breast muscle yield, and quality parameters respective to myopathy severity score at 43 d, regardless of dietary treatments, are shown in Table 9. There was a greater percentage breast muscle yield found in severe WB fillets (WB = 4) when compared to normal tissue (WB = 1) (P < 0.05). Sim-

ilarly, an increased breast muscle yield was observed (P < 0.05) in severe WS fillets. There were no WS scores of zero, indicating that no normal breast fillets in regard to WS were observed. However, the WS scores of 2 and 4 resulted in breast fillets with the greatest drip loss (P < 0.01). Blood physiology at 42 d, respective to 43 d myopathy scores, regardless of dietary treatment, is shown in Table 10. Broilers presenting with any signs of wooden breast (WB = 2, 3, 4) exhibited an increased circulating blood K (P < 0.01) as compared to broilers presenting with normal breast tissue (WB = 1). Furthermore, as WB score increased, pO2 decreased (R2 = 0.35; P < 0.05).

DISCUSSION Analyzed K values (Table 1) for all diets were less than calculated using basal NRC values for dietary ingredients (NRC, 1994). These data support other research findings (Borges et al., 2004) where expected values for dietary K were greater than were analyzed values, which indicated a potential K reduction in feed ingredients. Supplemental K (potassium carbonate) in our basal diets elevated these values and were intended to create a more desirable DEB (Mongin and Sauveur, 1977; Mongin, 1981). Furthermore, dietary analysis

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Available phosphorus4

Potassium3

Breast meat yield and quality2

8

LIVINGSTON ET AL.

Table 8. Effect of dietary potassium (K) and dietary phase levels of available phosphorus (AvP) on BW, hot carcass weight (HCW), dressing percentage (Dress), carcass moisture absorption (Pick-up), Pectoralis major weight (Pec. major), Pectoralis major yield (Pec. Yield), Wooden Breast (WB) and White Striping (WS) scores, pH, and moisture loss from breast (Drip Loss) at 43 d of age. BW and carcass1 Available phosphorus4

KK+ Decline Fixed SEM11 K-/Decline K+/Decline K-/Fixed K+/Fixed SEM11

BW

HCW

Dress5

Pick-up6

Pec. major

Pec. yield7

WB8

WS9

pH

Drip loss10

——–(g)——– 3934 3065 3870 3034

—–(%)—– 77.90 2.55 78.40 2.46

(g) 911 892

(%) 28.98 28.70

3.38 3.19

2.81 2.88

6.25 6.23

(%) 2.21 2.25

3871 3933

3025 3074

78.16 78.16

2.57 2.44

907 896

29.22 28.46

3.69a 2.88b

2.81 2.88

6.28 6.21

2.42 2.04

22

16

0.20

0.09

9

0.27

0.18

0.14

0.02

0.01

a,b

3935 3808 3933 3933

3060 2990 3070 3078

77.78 78.55 78.07 78.26

2.79 2.35 2.32 2.57

902 911 920 872

28.67 29.78a 29.29a 27.62b

3.63 3.75 3.13 2.63

2.63 3.00 3.00 2.75

6.30 6.25 6.21 6.22

2.35 2.48 2.07 2.01

41

31

0.41

0.18

18

0.48

0.33

0.28

0.04

0.22

0.25 0.99 0.48

0.60 0.50 0.07

0.57 0.02 0.35

0.82 0.82 0.27

0.64 0.15 0.60

0.88 0.11 0.69

(Probability > F) K P KxAvP

0.13 0.14 0.13

0.32 0.13 0.22

0.28 0.55 0.11

0.57 0.12 < 0.01

Means within a column lacking a common superscript differ significantly (P < 0.05). Main effect means calculated using 16 broilers at 43 d of age. 3 (K-) basal levels of K; (K+) 0.30, 0.34, 0.42% potassium carbonate (starter, grower, finisher). 4 (Decline) 0.45%, 0.40%, 0.35% AvP (starter, grower, and finisher); (Fixed) 0.45% AvP (starter, grower, and finisher). 5 Dress = HCW ÷ BW x 100%. 6 Pick-up = (chilled carcass weight)—HCW ÷ HCW x 100%. 7 Pec. Yield = Major weight ÷ Cold Carcass weight x 100%. 8 WB = wooden breast (1 = none, 2 = mild, 3 = moderate, 4 = severe). 9 WS = white Striping (1 = none, 2 = mild, 3 = moderate, 4 = severe). 10 Drip Loss = (initial Pec. major weight—final Pec. major weight) ÷ initial weight x 100. 11 SEM = Standard error of mean. a,b 1,2

determined our K+ finisher phase diets contained greater amounts of K than had been present in the K+ grower phase diets. This resulted in a grower to finisher phase increase of 0.72 to 0.77% K (K+/Decline) and 0.75 to 0.77% (K+/Fixed), whereas K-diets continued to decrease from phase to phase. This was obviously due to unexpected variation in our typical dietary ingredients in a manner similar to what might be expected commercially. Fixed dietary phase levels of AvP significantly improved overall FCR and generated numerically greater BW at 42 d, despite significantly reduced feed intake between 29 to 35 d. These broilers also exhibited reduced WB scores at 43 d of age. The yield of pectoralis major was reduced at 35 in broilers fed Decline diets (P < 0.10), while at 43 d the yield was numerically greater but statistically similar (P = 0.12). However, this indicates that broilers fed a Decline level of AvP displayed a possible compensatory gain in breast meat yield between 35 and 42 d to equal that of the Fixed AvP treatment. This increase in growth may have attributed to the greater WB scores found in the Decline fed broilers at 43 d, while Fixed AvP displayed reduced (P < 0.05) WB scores. The lowest WB scores were detected in the diet containing greater levels of both K and AvP. This could be attributed to an increased dietary DEB value and improved acid-base balance within the broiler, which could also account for the

improved FCR also observed when supplemental AvP and K were combined. During muscle contraction, the electrical potential of the cell is disrupted and K ions are driven from the muscle cells (Fenn, 1937, 1938). Skou (1965) determined that this process was mediated by an ATPdependent Na-K pump. Aldosterone is the primary hormonal regulator of many minerals including K (Palmer, 2015), and can affect the rate of K secretion and reabsorption via this membrane based pump (Skou, 1965; Palmer, 2015). The increase in blood K, as exhibited by broilers exhibiting signs of WB (Table 10) may have led to an increased K secretion from the kidney that ultimately needed to be replenished from dietary sources. Recent studies with modern broilers confirmed that the recommended DEB of 250 mEq per kg diet (Mongin and Sauveur, 1977; Mongin, 1981) was consistent with optimal live performance data. However, an increased DEB (near 300) was necessary to achieve similar BW and FCR in heat stressed broilers as control birds (Borges et al., 2004, 2007). This was attributed to the hemodilution that occurred as broilers were heat stressed, which was the result of an increased plasma volume associated with increased water intake (Borges et al., 2004). A similar mechanistic explanation may be applied to the present results where K+ diets contributed to thinner blood, as indicated by packed cell

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Potassium3

Breast meat yield and quality2

9

DIET AND BREAST MYOPATHIES

Table 9. Body weight (BW), hot carcass weight (HCW), dressing percentage (Dress), carcass moisture absorption (Pick-up), Pectoralis major weight (Pec. major), Pectoralis major yield (Pec. Yield), 24 h Pectoralis major pH, and 48 h Pectoralis major moisture loss (Drip Loss) in relationship to wooden breast (WB) and white striping (WS) scores of broilers at 43 d of age. BW and carcass1 WB3

(n)

BW

HCW

Breast meat yield and quality2

Dress4

Pick-up5

2 6 5 19

3860 3936 3924 3889

—–(g)—– 3010 3057 3080 3043

77.98 77.64 78.49 78.26

—–(%)—– 2.86 2.60 2.40 2.47

WS8 1 2 3 4

0 12 13 7

– 3900 3923 3866

– 3052 3055 3034

– 78.27 77.88 78.50

– 2.55 2.59 2.27

SEM9

22

16

0.20

0.09

WB WS

0.80 0.62

0.80 0.88

24 h pH

Drip loss7

(g) 854 893 873 916

(%) 27.55b 28.48a,b 27.67b 29.40a

6.09 6.20 6.23 6.28

(%) 1.76 2.09 1.72 2.45

– 894 889 936

– 28.58b 28.35b 30.18a

– 6.25 6.22 6.28

– 2.30A 1.87B 2.73A

0.27

0.02

0.11

0.05 0.02

0.15 0.54

0.07 < 0.01

9 (Probability > F) 0.73 0.16 0.42 0.11

0.61 0.48

Means within a column lacking a common superscript differ significantly (P < 0.05). Means within a column lacking a common superscript differ significantly (P < 0.01). 1,2 Means calculated using 32 broilers at 43 d of age. 3 WB = wooden breast score (1 = none, 2 = mild, 3 = moderate, 4 = severe), 4 Dress = HCW ÷ BW x 100%. 5 Pick-up = (chilled carcass weight—HCW) ÷ HCW x 100%. 6 Pec. Yield = Pectoralis major weight ÷ Cold Carcass weight x 100%. 7 Drip Loss = (initial Pectoralis major weight—final weight) ÷ initial weight x 100. 8 WS = white striping score (1 = none, 2 = mild, 3 = moderate, 4 = severe). 9 SEM = Harmonic standard error of mean. a,b

A,B

Table 10. Broiler blood pH, sodium (Na), potassium (K), hemoglobin (Hgb), packed cell volume (PCV), glucose (Glu), ionized calcium (iCa), saturated oxygen (S O2 ), partial pressure of oxygen (P O2 ), partial pressure of carbon dioxide (P CO2 ), total carbon dioxide (T CO2 ), bicarbonate (HCO3 ), base excess in the extra cellular fluid (BEecf) at 42 d, in relationship to 43 d Wooden Breast (WB) and White Striping (WS) scores. WB1,2

(n)

pH

Na

K

Hgb

PCV

(g/dL) 7.15 7.18 6.80 7.16

(%) 21.00 21.67 20.00 21.05

—–(mg/dL)—– 246 1.36 254 1.45 253 1.46 251 1.44

(%) 83.50 73.17 72.60 69.74

—–(mmHg)—– 49.00 44.25 43.00 57.40 42.40 52.10 39.89 50.90

—–(mmol/L)—– 29.50 28.15 3.50 30.66 29.07 2.83 29.00 27.54 1.80 29.84 28.46 3.00

– 248 257 249

– 70.50 74.85 67.86

– 40.67 44.31 38.14

– 53.63 49.97 52.53

– 30.33 29.62 29.43

– 28.84 28.22 28.03

– 3.00 3.00 2.15

2.27 0.01 1.67 (Probability > F) 0.90 0.40 0.25 0.17 0.43 0.25

1.27

1.48

0.46

0.42

0.45

0.29 0.16

0.21 0.56

0.78 0.71

0.78 0.72

0.81 0.74

1 2 3 4

2 6 5 19

6.09 6.20 6.23 6.28

—–(mmol/L)—– 147.00 4.75B 146.83 6.25A 144.40 5.76A 145.42 5.87A

WS1,3 1 2 3 4

0 12 13 7

– 6.25 6.22 6.28

– 146.08 145.77 144.57

– 6.06 5.61 5.97

– 7.30 6.99 7.00

– 21.50 20.54 20.57

SEM9

0.01

0.34

0.10

0.13

0.38

0.15 0.55

0.13 0.25

0.01 0.11

0.80 0.54

0.80 0.49

WB WS

Glu

iCa

– 1.45 1.43 1.41

S O2

P O2

P CO2

T CO2

HCO3

BEecf

Means within a column lacking a common superscript differ significantly (P < 0.01). Means calculated using 32 individual broilers at 42 d. 2 WB = wooden breast score (1 = none, 2 = mild, 3 = moderate, 4 = severe), 3 WS = white striping score (1 = none, 2 = mild, 3 = moderate, 4 = severe). 4 SEM = Harmonic standard error of mean. A,B 1

volume and hemoglobin values at 29 d (Table 5). However, these differences did not persist to 42 d (Table 6), which may be attributed to the lower than expected analyzed values of K in the finisher diets. This may have also been attributed to increased water intake (Deyhim and Teeter, 1991). Dietary K (K+) was able to improve blood pH, reduce pCO2 , and created thinner blood, which should have contributed to improved vascular circulation and improved ability to remove H+

from the muscle tissues. This should have resulted in reduced WB scores. The blood physiology of broilers exhibiting specific WB scores, independent of treatment, provided greater insight into these myopic conditions. The highly significant differences in blood K between normal broilers and those presenting with any sign of WB indicated a muscle cell voltage gradient disruption and/or cell wall leakage. Increased blood K has also been

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1 2 3 4

Pec. yield6

Pec. major

10

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REFERENCES Borges, S. A., A. V. Fischer da Silva, A. Majorka, D. M. Hooge, and K. R. Cummings. 2004. Physiological responses of broiler chickens to heat stress and dietary electrolyte balance (sodium plus potassium minus chloride, milliequivalents per kilogram). Poult. Sci. 83:1551–1558. Borges, S. A., A. V. F. Da Silva, and A. Maiorka. 2007. Acid-base balance in broilers. Worlds Poult. Sci. J. 63:73–81. Brewer, V. B., V. A. Kuttappan, J. L. Emmert, J.-F. C. Meullenet, and C. M. Owens. 2012. Big-bird programs: effect of strain, sex, and debone time on meat quality of broilers. Poult. Sci. 91:248– 254. Deyhim, F., and R. G. Teeter. 1991. Research note: sodium and potassium chloride drinking water supplementation effects on acid-base balance and plasma corticosterone in broilers reared in thermoneutral and heat-distressed environments. Poult. Sci. 70:2551–2553. Fenn, W. O. 1937. Loss of potassium from stimulated frog. Am. J. Physiol. 120:675–680.

Fenn, W. O. 1938. Factors affecting the loss of potassium from stimulated muscle. Am. J. Physiol. 124:213–229. Hamm, L. L., and E. E. Simon. 1987. Roles and mechanisms of urinary buffer excretion. Am. J. Physiol. 253:F595–605. Kuttappan, V. A., Y. S. Lee, G. F. Erf, J.-F. C. Meullenet, S. R. McKee, and C. M. Owens. 2012. Consumer acceptance of visual appearance of broiler breast meat with varying degrees of white striping. Poult. Sci. 91:1240–1247. Kuttappan, V. A., H. L. Shivaprasad, D. P. Shaw, B. A. Valentine, B. M. Hargis, F. D. Clark, S. R. McKee, and C. M. Owens. 2013. Pathological changes associated with white striping in broiler breast muscles. Poult. Sci. 92:331–338. Leytem, A. B., P. W. Plumstead, R. O. Maguire, P. et. Kwanyuen, and J. Brake. 2007. What aspect of dietary modification in broilers controls litter water-soluble phosphorus J. Environ. Qual. 36:453–463. Leytem, A. B., P. W. Plumstead, R. O. Maguire, P. Kwanyuen, J. W. Burton, and J. Brake. 2008. Interaction of calcium and phytate in broiler diets. 2. Effects on total and soluble phosphorus excretion. Poult. Sci. 87:459–467. Livingston, M. L., P. R. Ferket, J. Brake, and K. A. Livingston. 2018. Dietary amino acids under hypoxic conditions exacerbates muscle myopathies including wooden breast and white stripping. Poult. Sci. 0:1–11. Maguire, R. O., Z. Dou, J. T. Sims, J. Brake, and B. C. Joern. 2005. Dietary strategies for reduced phosphorus excretion and improved water quality. J. Environ. Qual. 34:2093–2103. Mizgala, C. L., and G. A. Quamme. 1985. Renal handling of phosphate. Physiol. Rev. 65:431–466. Mongin, P. 1981. Recent advances in dietary anion-cation balance: applications in poultry. Proc. Nutr. Soc. 40:285–294. Mongin, P., and B. Sauveur. 1977. Interrelationships between mineral nutrition, acid-base balance, growth and cartilage abnormalities. Pages 235–347 In Growth and Poultry Meat Production. K. N. Boorman, and B. J. Wilson, eds. Brit. Poult. Sci., Edinburgh, UK. Mudalal, S., E. Babini, C. Cavani, and M. Petracci. 2014. Quantity and functionality of protein fractions in chicken breast fillets affected by white striping. Poult. Sci. 93:2108–2116. NRC. 1994. National Research Council. Nutrient Requirements of Poultry. 8th ed. Natl. Acad. Press, Washington, DC. Oliveira, J. E., L. F. T. Albino, H. S. Rostagno, L. E. P´ aez, and D. C. O. Carvalho. 2005. Dietary levels of potassium for broiler chickens. Rev. Bras. Cienc. Avic. 7:33–37. Palmer, B. F. 2015. Regulation of potassium homeostasis. Clin. J. Am. Soc. Nephrol. 10:1050–1060. Petracci, M., S. Mudalal, A. Bonfiglio, and C. Cavani. 2013. Occurrence of white striping under commercial conditions and its impact on breast meat quality in broiler chickens. Poult. Sci. 92:1670–1675. Petracci, M., S. Mudalal, F. Soglia, and C. Cavani. 2015. Meat quality in fast-growing broiler chickens. Worlds Poult. Sci. J. 71:363– 374. Rinehart, K. E., and J. C. Rogler. 1968. Effects of a dietary potassium deficiency on protein synthesis in the young chick. J. Nutr. 95:627–632. SAS Institute Inc. SAS user’s guide: Statistics, Version 8.1. 2009. Sihvo, H. K., K. Immonen, and E. Puolanne. 2014. Myodegeneration with fibrosis and regeneration in the pectoralis major muscle of broilers. Vet Pathol 51:619–623. Skou, J. C. 1965. Enzymatic basis for active transport of Na+ and K+ across cell membrane. Physiol. Rev. 45:596–618. Trocino, A., A. Piccirillo, M. Birolo, G. Radaelli, D. Bertotto, E. Filiou, and M. Petracci. 2015. Effect of genotype, gender and feed restriction on growth, meat quality and the occurrence of white striping and wooden breast in broiler chickens. Poult. Sci. 94:2996–3004. United States Department of Agriculture. 2017. Food safety and inspection services. Disposition instructions for “woody breast” and “white striping” poultry conditions. Notice:35–17.

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associated with intermittent muscle cell tetanus (Fenn, 1938). There was also a trend towards increased blood P CO2 and decreased S O2 and P O2 as the severity of WB increased (Table 10). This trend may become significant with greater replicates and is supported the most recently published work what does indicated a coorilation between WB and decreased S O2 and P O2 along with increased P CO2 (Livingston et al., 2018). This suggested a condition of hypoxia that may have been associated with the WB myopathy. Although these values were not significantly different, the correlation of blood O2 to WB scores should not be ignored (P < 0.05), Assuming that a 95% probability of detecting an effect was desired using a two-tailed test, then a power calculation revealed the number of experimental units should be 12 or more for each severity group (1 to 4). Although this experiment did not achieve this desired level of significance, we have now obtained the SEM and associated sample size necessary to design an experiment capable of detecting these effects. Maintaining levels of AvP in the grower and finisher diet phases like those found in the starter phase appeared to reduce WB myopathies when compared to decreased dietary phase levels of AvP. However, This may come at the expense of breast muscle yield. Increasing dietary K and AvP levels may have created a more desirable acid-base balance, probably by improving H+ removal through the kidney phosphate buffer system, a greater DEB, and replenishing muscle intracellular fluid concentrations of K lost during breast muscle contractions. However, the amount of K in finisher diets should not equal or exceed the amount within the grower diet, and should be formulated lower than that found in this study. Overall, the fixed levels of AvP among dietary phases decreased WB significantly, while coupled with increased dietary K exhibited the greatest improvement in FCR.