Live and processing performance of broiler chickens fed diets supplemented with complexed zinc

©2010 Poultry Science Association, Inc.

Live and processing performance of broiler chickens fed diets supplemented with complexed zinc B. Saenmahayak, S. F. Bilgili,1 J. B. Hess, and M. Singh Department of Poultry Science, Auburn University, Auburn, AL 36849-5416

SUMMARY In this study, the influence of complexed Zn (C-Zn) supplementation on live performance (BW, feed conversion, and mortality), skin quality (incidence of sores, scabs, and scratches; footpad dermatitis), processing yields, and meat quality of broiler chickens was assessed at 49 d of age. A total of 1,440 male broilers were assigned to 3 dietary treatments: 1) an inorganic Zn control diet (IC; 80 ppm of ZnSO4), 2) 40 ppm of ZnSO4 in the IC diet replaced with C-Zn (IC-C-Zn), and 3) an additional 40 ppm of C-Zn added on top of the IC diet (IC+C-Zn). Each treatment was provided in a 3-stage feeding program. Body weight and feed conversion were significantly (P < 0.05) improved with IC-C-Zn compared with the IC treatment. The IC+C-Zn treatment also improved feed conversion, but not final BW compared with the IC treatment. No differences in carcass and component yields were detected because of dietary treatments. The proportion of birds with skin lesions decreased (P < 0.05) from 42.7% (IC) to 9.6% (IC-C-Zn). In addition, deboned fillet and total breast yields were significantly higher (P < 0.05) in the IC+C-Zn treatment than in the IC treatment. The incidence and severity of footpad dermatitis was significantly reduced (P < 0.05) with both C-Zn treatments. The breast fillet quality attributes measured did not show any differences (P > 0.05) due to dietary treatments. Inclusion level and source of dietary Zn had a significant influence on broiler live and processing performance in this study. Key words: broiler, complexed zinc, pododermatitis, skin quality 2010 J. Appl. Poult. Res. 19:334–340 doi:10.3382/japr.2010-00166

DESCRIPTION OF PROBLEM Zinc is an important trace mineral in animal nutrition involved in many metabolic processes, including growth, skin quality, and wound healing. Zinc is a cofactor for several enzymes involved in the synthesis of proteins as well as in the synthetic and catabolic rates of RNA and DNA metabolism [1]. The bioavailability of trace mineral supplements from inorganic sources can be low, and their complexes with more readily available compounds can enhance mineral absorption [2, 3]. Organic forms of trace 1

Corresponding author: [email protected]

elements such as Zn have increasingly been used in the poultry feed industry. Greater bioefficacy of organic Zn sources, compared with their inorganic forms, including ZnO and ZnSO4, have been reported [2, 4]. Enhanced bioavailability of a mineral source can potentially reduce the amount of a mineral that is added to a diet to meet mineral nutritional requirements, leading to reduced amounts of mineral excreted by birds [5]. Although organic forms of the trace element have increasingly been used by the poultry feed industry [2, 5], the use of organic complexes of trace elements such as Zn-lysine and Zn-meth-

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Primary Audience: Nutritionists, Production and Processing Personnel

Saenmahayak et al.: INFLUENCE OF COMPLEXED ZINC

MATERIALS AND METHODS

randomly placed in 24 floor pens in a curtain-sided, naturally ventilated concrete-floored house. The pens were 1.70 × 2.30 m in dimension (8 pens/treatment; 60 birds/pen, or 15 birds/m2) and bedded with litter of new pine shavings to cover the concrete floors. The experimental diets (Table 1) were provided in a 3-stage feeding program to 49 d of age. The feeding program consisted of a crumbled starter diet (1 to 15 d of age), a pelleted grower diet (16 to 42 d of age), and a withdrawal diet (43 to 48 d of age). There were 3 dietary treatments: 1) an inorganic control (IC; 80 ppm of ZnSO4), 2) 40 ppm of complexed Zn (C-Zn), with complexed Zn replacing 40 ppm of Zn in the IC (IC-C-Zn), and 3) 40 ppm of C-Zn, with complexed Zn providing an additional 40 ppm of Zn on top of the IC (IC+C-Zn) [16]. All birds were weighed at 15, 42, and 48 d of age on a per-pen basis, and BW, adjusted feed conversion, and mortality were determined cumulatively. The incidence and severity of FPD was scored at 48 d of age on all birds by using a visual ranking system [17]. At 49 d of age, a subsample of 10 birds were randomly chosen from each pen (240 birds in total) and processed at the Auburn University Poultry Science Department Processing Plant, simulating commercial processing practices. Carcasses were chilled for 1.5 h in static slush-ice and subjected to blind grading for carcass and skin quality defects, including wing bruises and fractures, drumstick bruises and fractures, thigh bruises and SSS, back bruises and SSS, and overall carcass grade [18]. Whole carcass, abdominal fat, parts (wings, drumsticks, and thighs), and deboned breast (fillet and tender) weights and yields were also determined. Breast fillets from 3 birds per pen were randomly selected to assess meat quality attributes [19] of drip loss (24 and 48 h), cook loss, water-holding capacity [20], and color (L* = lightness, a* = redness, and b* = yellowness) [21]. The data were analyzed using the GLM procedure of SAS 9.1.2 software [22]. All percentage data were transformed to arcsine values before analysis, and Tukey’s test was used to compare and separate means when main effects were significant (P < 0.05).

Diets and Experimental Design

Bird Care

A total of 1,440 Ross × Ross 708 one-day-old broilers (obtained from a local hatchery) were

Birds were managed according to normal husbandry practices and were killed with full con-

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ionine has received more attention because of their potential for greater bioavailability. Zinc plays a role in the cross-linking process of collagen, which contributes to the skin tensile strength and wound healing [6]. Therefore, it is speculated that organic Zn compounds may enhance growth and skin quality performance in poultry. Skin-associated downgrading problems (dermatitis, sores, cuts, and tears) continue to cause substantial economic losses to the broiler industry worldwide. Footpad dermatitis (FPD) is a type of skin dermatitis in broiler chickens affecting the footpads (also referred to as paw burns or ammonia burns). Several factors contribute to the prevalence of FPD in broilers, including nutrient excesses, deficiencies, or both; litter type [7] and moisture [8]; and high stocking density [9–11]. Skin lesions, such as sores, scabs, and scratches (SSS), or underlying infections (i.e., cellulitis) mostly occur during the various stages of the grow-out phase and accentuate skin tearing during processing [12]. Many suboptimal flock management conditions (overcrowding, poor feathering, inadequate water and feeder space, and excessive bird activity) or improper handling during catching [13] can contribute to skin quality problems. Male broilers of slow-feathering strains are more prone to scratches because their skin is exposed for longer periods of time. Environmental conditions, such as high temperature and humidity, can cause skin problems caused by migration and crowding in the house [14]. Nutrition, especially the calorie:protein ratio, also affects skin quality through fat deposition in the skin. Skin with a greater percentage of fat and less total protein results in reduced skin strength and more frequent skin tears during processing [15]. Little information is available regarding the effects of complexed organic Zn sources on broiler carcass and meat quality [14]. The objectives of this study were to evaluate live performance, carcass and parts yields, skin characteristics (skin strength and quality), and meat quality of broilers fed inorganic or organic sources of Zn to 49 d of age.

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336 Table 1. Nutrient composition of experimental diets1 Starter Item

IC

IC-C-Zn IC+C-Zn

IC 62.52 27.87 1.35 1.00 0.43 0.23 0.25 0.25 0.03 0.08

Withdrawal

IC-C-Zn IC+C-Zn 62.52 27.87 1.35 1.00 0.43 0.23 0.25 0.25 0.03 0.08

62.52 27.87 1.35 1.00 0.43 0.23 0.25 0.25 0.03 0.08

21.44 22.50 21.50 2,710 2,690 2,670 1.15 0.99 1.00 0.52 0.48 0.49 199 174 244 119 100 101

IC 71.71 20.67 1.11 0.89 0.51 0.19 0.25 0.25 0.08 —

IC-C-Zn IC+C-Zn 71.71 20.67 1.11 0.89 0.51 0.19 0.25 0.25 0.08 —

71.71 20.67 1.11 0.89 0.51 0.19 0.25 0.25 0.08 —

19.00 18.75 17.31 2,670 2,670 2,670 0.89 0.78 0.93 0.42 0.38 0.43 146 156 232 87 84 101

1

Starter diet fed from d 1 to 15; grower diet fed from d 16 to 42; withdrawal diet fed from d 43 to 49. IC = inorganic control (80 ppm of ZnSO4); IC-C-Zn = complexed Zn replaced 40 ppm of Zn from ZnSO4; IC+C-Zn = complexed Zn provided an additional 40 ppm of Zn on top of the IC diet. 2 Trace mineral premix supplied the following per kilogram of diet: Mn, 143 mg; Zn, 121 mg; Fe, 13 mg; Cu, 13 mg; I, 2.2 mg; and Se, 0.7 mg. 3 Vitamin premix supplied the following per kilogram of diet: vitamin A, 16,183 IU; vitamin D3, 4,851 IU; vitamin E, 16.6 IU; vitamin B12, 0.04 mg; riboflavin, 12 mg; biotin, 0.05 mg; niacin, 80 mg; pantothenic acid, 29 mg; choline, 1,102 mg; menadione, 4.8 mg; folic acid, 1.1 mg; pyridoxine, 4.4 mg; and thiamine, 2.2 mg. 4 Monensin Na premix, Coban 60 (Elanco Animal Health, Indianapolis, IN).

sideration of animal welfare. The experiments were conducted according to the guidelines and approval of the Institutional Animal Care and Use Committee of Auburn University.

RESULTS AND DISCUSSION Broilers reared on the IC-C-Zn diet showed improvements (P < 0.05) in live performance over those reared on the IC diet. Birds fed ICC-Zn had higher BW (P < 0.05) as compared with those in the IC treatment at both 42 and 48 d of age (Table 2). Feed conversion was also improved (P < 0.05) with both C-Zn treatments at 42 and 48 d of age; however, no differences (P > 0.05) were detected in mortality between treatments throughout the study. The results observed in our study concur with those of several other studies in which improvements in broiler performance were reported when broiler feeds were supplemented with higher levels of dietary Zn, both in inorganic [23, 24] and organic forms [25,

26]. In addition, others have reported improved broiler performance as a result of replacing 40 ppm of ZnSO4 with 40 ppm of Zn amino acid complex [27, 28]. However, the results obtained in our study are contrary to those reported by the NRC [29], which reported that regardless of its form, dietary supplementation of Zn in excess of 40 mg/kg of feed did not improve the growth performance, leg abnormalities, and meat yields of broilers. These conflicting effects of dietary Zn on growth performance may be due to the variable amount of Zn present in the feed ingredients used because the presence of other dietary ligands can form insoluble complexes with Zn and prevent its absorption [30, 31]. Dietary Zn from organic sources might be absorbed intact and function differently from Zn from inorganic sources after absorption. Zinc may be transferred to enzymes as a ligand complex, and the ligand could influence enzyme activity. The combination of ZnSO4 and Zn amino acid complexed in broiler diets may result in selective metabolism

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Ingredient, %   Ground corn 56.60 56.60 56.60   Soybean meal (48% CP) 33.34 33.34 33.34   Dicalcium phosphate 1.47 1.47 1.47   Limestone 1.15 1.15 1.15   Salt 0.42 0.42 0.42   dl-Methionine 0.26 0.26 0.26   Trace mineral premix2 0.25 0.25 0.25   Vitamin premix3 0.25 0.25 0.25 0.10 0.10 0.10   l-Lysine   Coccidiostat4 0.08 0.08 0.08 Nutrient analysis   CP % 23.38 24.69 25.13   ME, kcal/kg 2,710 2,690 2,650   Ca % 1.16 1.18 1.16   Available P % 0.54 0.51 0.54   Zn, ppm 209 205 299   Mn, ppm 121 120 134

Grower

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Table 2. Effect of Zn source on broiler live performance from 1 to 48 d of age 1 to 15 d Factor 2

Diet   IC   IC-C-Zn   IC+C-Zn SEM3

BW, g

FC1

NS 481 493 481 9.87

NS 1.177 1.185 1.186 0.017

1 to 42 d

Mortality, % NS 0.3 0.3 0.3 0.2

BW, g * 2,596b 2,670a 2,664ab 19.38

1 to 48 d

FC

Mort, %

* 1.643a 1.614b 1.614b 0.007

NS 0.9 1.4 1.3 0.3

BW, g ** 3,140b 3,241a 3,209ab 20.96

FC

Mortality, %

** 1.736a 1.701b 1.713b 0.006

NS 1.4 1.9 1.5 0.4

a,b

Means within a category with different superscripts differ significantly. FC = feed conversion adjusted for mortality. 2 IC = inorganic control (80 ppm of ZnSO4); IC-C-Zn = complexed Zn replaced 40 ppm of Zn from ZnSO4; IC+C-Zn = complexed Zn provided an additional 40 ppm of Zn on top of the IC diet. 3 SEM = pooled SEM. *P < 0.05; **P < 0.01; NS, P > 0.05. 1

tent with those reported for broiler footpad [15] and dairy hoof scores [35]. The carcass and skin quality evaluations are summarized in Table 3. In this trial, we used a slow-feathering strain and a high stocking density. However, no significant effect (P > 0.05) attributable to dietary treatments was noted for most of the carcass defects and the proportion of grade A carcasses. Thigh SSS were improved with C-Zn, particularly in the IC-C-Zn treatment. Most of the skin lesions were located on the thigh and pelvic back region of the broilers, where feathering is usually marginal. Collagen is the major fibrous element of skin, and the higher collagen content in birds fed higher levels of organic Zn helps in holding the cells more tightly together in discrete units [13]. Zinc is necessary to promote protein synthesis, collagen formation, and optimal enzyme activity.

Table 3. Effect of Zn source on broiler carcass quality at the end of grow-out (49 d) Wing Factor Diet2   IC   IC-C-Zn   IC+C-Zn SEM3 a,b

Drumstick

Bruised, %

Broken, %

NS 4.7 9.9 18.4 4.2

NS 24.7 17.5 16.2 4.6

Bruised, Broken, % % NS 6.5 7.1 1.3 2.4

NS 2.6 0 0 1.0

Thigh

Back

Bruised, %

SSS,1 %

NS 0 1.4 0 0.8

*** 42.7a 9.6b 26.3ab 4.9

Bruised, SSS, Breast Grade, % % bruise, % % NS 7.0 3.0 4.7 3.2

NS 7.2 4.0 4.4 2.4

NS 3.2 0 1.6 1.5

NS 55.6 71.1 63.9 5.6

Means within a category with different superscripts differ significantly. Scores, scabs, and scratches. 2 IC = inorganic control (80 ppm of ZnSO4); IC-C-Zn = complexed Zn replaced 40 ppm of Zn from ZnSO4; IC+C-Zn = complexed Zn provided an additional 40 ppm of Zn on top of the IC diet. 3 SEM = pooled SEM. ***P < 0.001; NS, P > 0.05. 1

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of Zn by different enzymes and may enhance broiler performance [32, 33]. The use of organic mineral sources can improve intestinal absorption of trace elements because organic mineral sources reduce interference from agents that form insoluble complexes with the ionic trace elements [34]. The incidence and severity of FPD was significantly (P < 0.05) improved with both C-Zn treatments at 48 d of age (Figure 1). The percentage of birds without FPD was greatest for the C-Zn treatments. In addition, FPD severity (i.e., proportion of mild and severe lesions) was reduced in birds fed the C-Zn treatments. Footpad quality depends on the ability of the broiler to maintain skin integrity when faced with irritation from friction, moisture, and fecal contact associated with the litter. These improvements in skin integrity from feeding C-Zn are consis-

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Table 4. Effect of Zn source on meat quality attributes of processed broilers at 49 d of age Drip loss, % Factor1 2

Diet   IC   IC-C-Zn   IC+C-Zn SEM3

24 h

48 h

Cook loss, %

NS 0.9 1.1 0.9 0.1

NS 2.1 2.4 2.5 0.2

NS 27.5 26.2 27.6 1.1

Color2

WHC, %

L*

a*

b*

NS 33.1 34.8 35.0 3.6

NS 60.52 60.54 60.34 0.39

* 5.99ab 6.39a 6.23ab 0.16

NS 12.87 13.25 13.11 0.33

a,b

Means within a category with different superscripts differ significantly. L* = lightness; a* = redness; b* = yellowness. 2 IC = inorganic control (80 ppm of ZnSO4); IC-C-Zn = complexed Zn replaced 40 ppm of Zn from ZnSO4; IC+C-Zn = complexed Zn provided an additional 40 ppm of Zn on top of the IC diet. 3 SEM = pooled SEM. *P < 0.05; NS, P > 0.05. 1

former [6]. Moreover, collagen gives flexibility to the skin that protects the skin from tearing during broiler rearing on the farm and handling in the marketing process. At 49 d of age, chilled carcass, wing, and drumstick weights and yields were not different among the dietary treatments. Breast fillet and total breast (fillet + tender) yields were significantly higher for birds fed the IC+C-Zn treatment compared with the IC treatment (Figure

Figure 1. Incidence and severity of footpad dermatitis (FPD) after treatment with the inorganic control diet (IC; 80 ppm of ZnSO4), complexed Zn replacing 40 ppm of Zn from ZnSO4 (IC-C-Zn), or complexed Zn providing an additional 40 ppm of Zn on top of the IC diet (IC+C-Zn). None = no lesions present; mild = lesions <10 mm; severe = lesions ≥10 mm. Means within a category with different letters (a, b) differ significantly (P < 0.05). SEM for no lesions = 3.8%; mild lesions = 3.2%; and severe lesions = 3.2%.

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The greatest activity of Zn in wound healing occurs during epithelialization, when large stores of Zn in the skin serve as a convenient source of the mineral [29]. Although collagen appears to be the major determinant of skin strength, the rate of cross-linking and the state of maturation of the collagen may also play a role [8]. Skin strength has been shown to be different for fastfeathering and slow-feathering broiler crosses, with the latter having less elastic skin than the

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2). McNaughton and Shugel [36] reported that feeding Zn-methionine and Mn-methionine increased breast meat yield in broilers. Bonomi et al. [37] also reported that carcass and meat yields improved when ducks were fed chelated Zn and Mn complexes. However, others [13, 38] could not show improvements in breast yield when different levels of inorganic Zn and Mn were fed to broilers. Meat quality attributes (drip loss, cooking loss, and water-holding capacity) measured during this study were not influenced by Zn sources (P > 0.05) at 49 d of age (Table 4). Breast meat had an increased redness value (greater a* value; P < 0.05) resulting from the 2 C-Zn treatments (Table 4). This effect may be due to the ability of Zn to bind myoglobin and increase its oxygenation. Zinc also inhibits mitochondrial respiration and decreases the production of free radicals by acting as an antioxidant, thus facilitating the maintenance of meat color [38–40].

CONCLUSIONS AND APPLICATIONS

1. Body weights and feed conversions were observed to be the best in broilers fed di-





ets supplemented with C-Zn compared with the other diets. 2. When C-Zn replaced 40 ppm of ZnSO4, broilers had the most improvement in skin quality, breast meat yield, and FPD severity and incidence. 3. When C-Zn replaced 40 ppm of ZnSO4, broiler breast meat fillets had the most redness (highest a* values).

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Figure 2. Breast fillet yields after dietary treatment with the inorganic control diet (IC; 80 ppm of ZnSO4), complexed Zn replacing 40 ppm of Zn from ZnSO4 (IC-C-Zn), or complexed Zn providing an additional 40 ppm of Zn on top of the IC diet (IC+C-Zn). Means within a category with different letters (a, b) differ significantly (P < 0.05). SEM for fillets = 0.2%; tenders = 0.1%; and total breast = 0.2%.

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