Effect of selenium sources on growth performance and tissue selenium retention in yellow broiler chicks

Abstract

An experiment was conducted to investigate the effects of selenium (Se) sources on growth performance and tissue Se retention in yellow chicks fed a conventional corn-soybean meal basal diet. A total of 2250 one-day-old chicks were fed a Se-unsupplemented corn-soybean meal basal diet (containing 0.10 mg of Se/kg) for six days, and then chicks were assigned by body weight to 1 of 5 treatments with 6 replicates of 75 birds each floor pen in a completely randomized design. Broilers were fed the basal diet (control) or basal diet supplemented with 0.3 mg/kg of Se from sodium selenite, Nano elemental Se, Se yeast A or B for 10 days. The results showed that Se sources did not significantly (P > 0.52) affect growth performance. Se sources significantly affected (P < 0.05) Se concentrations in liver and breast muscle, in which chicks fed the diet supplemented with Se yeast B had higher (P < 0.05) tissue Se concentrations than those fed the diet supplemented with sodium selenite or Nano elemental Se. No differences (P > 0.66) were observed in liver and breast muscle Se concentrations among sodium selenite, Nano elemental Se and Se yeast A. Therefore, the new procedure used in this experiment could detect the differences of the effectiveness among Se sources, and Se yeast B was the most effective Se source for yellow broiler chicks.

Keywords:

• broiler
• selenium
• retention

1. Introduction

Selenium (Se) is well known to be essential for growth (Yoon et al. 2007; Wang and Xu 2008), feather development (Edens et al. 2001; Perić et al. 2009), immune competence (Cai et al. 2012; Liao et al. 2012), antioxidant (Peng et al. 2007; Zhou and Wang 2011) and reproduction (Poley et al. 1937; Leeson et al. 2008) of chickens. Inorganic Se salts, such as sodium selenite, are generally supplemented in diets to meet the Se requirement of chickens (Perić et al. 2009). When the FDA first permitted the usage of Se yeast in poultry diets in 2001, Se yeast products have been developed and reported to be more effective than inorganic Se used in chicken feeds (Rayman 2004; Ševčíková et al. 2006; Yoon et al. 2007). Nano red elemental Se was a new Se source, which has novel characteristics such as a large surface area, high surface activity, high catalytic efficiency, strong adsorbing ability and low toxicity (Zhang et al. 2001; Peng et al. 2007; Wang et al. 2007). Mennini (2012) reported that Nano-Se and selenite could similarly increase tissue Se and glutathione peroxidases in Se-deficient rats, which indicated that the bioavailability of the two Se forms was similar. Zhou and Wang (2011) also reported that diet supplemented with 0.30 mg/kg of Nano-Se could effectively increase the growth performance of chickens and the Se content of organs. However, the effectiveness of sodium selenite, Se yeast and Nano red elemental Se for yellow broiler has not been experimentally verified directly. In addition, the reported procedure for estimating the effectiveness of different Se sources in broiler generally need a long time (21–42 days), and birds were always fed added Se diets during the experiment. Indeed, birds depleted body Se by feeding a Se-deficient diet and then fed added Se diets might be sensitive to determine the effectiveness of different Se sources for broiler chicks in a short time. Therefore, the objective of this study was to determine the effects of Se sources on growth performance and tissue Se retention of yellow broiler chicks by feeding a Se-deficient diet and then fed added Se diet for a short time, in order to develop a new procedure for evaluating the effectiveness of Se sources.

2. Material and methods

2.1. Experimental design, diets and birds

A completely randomized design was adopted in this experiment. The basal diet (control, Table 1, containing 0.10 mg Se/kg of diet by analysis) was formulated to meet or exceed the nutrient requirements of growing yellow broilers from 1 to 4 week of age recommended by Ministry of Agriculture of People's Republic of China (2004) except for Se. The added Se diets were formulated by supplementing 0.30 mg Se/kg of diet from sodium selenite (containing 1.0 % Se on a basis of analysis), Nano elemental Se (containing 0.09 % Se on a basis of analysis), Se yeast A (containing 0.21 % Se on a basis of analysis) or Se yeast B (containing 0.20 % Se on a basis of analysis), respectively.

Table 1. Composition of the basal diets for broilers (as-fed basis).

Item	g/kg diet
Ingredient (%)
Ground corn	563.67
Soybean meal	369.00
Soybean oil	24.60
Dicalcium phosphate	19.20
Calcium carbonate	9.10
Sodium bicarbonate	1.20
Sodium chloride	2.70
DL-Methionine	2.31
Lysine·HCl	0.22
Premix^a	7.00
Cornstarch + Se^b	1.00
Chemical composition
Dry matter^c	87.0
Metabolizable energy (MJ/kg)	12.2
Crude protein^c	20.5
Digestible Lys	1.05
digestible TSAA	0.80
Digestible Thr	0.68
Digestible Arg	1.25
Digestible Trp	0.22
Calcium^c	0.90
Nonphytate phosphorus^c	0.45

TSAA, total sulfur amino acids.

^a Provided per kilogram of diet: vitamin A (all-trans retinol acetate), 10,000 IU; cholecalciferol, 3000 IU; vitamin E (all-rac-α-tocopherolacetate), 16 IU; vitamin K (menadione sodium bisulfate), 2.0 mg; thiamin (thiamin mononitrate), 2.0 mg; riboflavin, 6.4 mg; vitamin B6, 2.0 mg; vitamin B12, 0.012 mg; calcium pantothenate, 10 mg; niacin, 26 mg; folic acid, 1.0 mg; biotin, 0.10 mg; choline (choline chloride), 1000 mg; Cu (CuSO₄·5H₂O), 8 mg; Mn (MnSO₄·H₂O), 80 mg; Fe (FeSO₄·7H₂O), 80 mg; Zn (ZnSO₄·7H₂O), 40 mg; and I (KI).

^b Se sources added in place of equivalent weights of cornstarch.

^c Determined by analysis. Each value was based on triplicate determinations.

All experimental procedures were approved by the Office of the Guangdong Veterinarians. Two thousand five hundred 1-day-old male yellow broiler chicks were obtained from a local hatchery (Wen's Foodstuffs Group Corporation Ltd., Yunfu, People's Republic of China) and housed in electrically heated, thermostatically controlled, wire-floored pens equipped with fibreglass feeders and waterers. Each floor pen was 7.5 m², and a stocking density was 10 birds/m². Feed and tap water with no detectable Se were available ad libitum and birds were maintained on a 24-h constant light schedule. All birds were fed a basal diet from day 1 to 6 to deplete body-stored Se. At 7 days of age, a total of 2250 chicks with similar body weight (75 ± 3 g) were selected and randomly allotted to 1 of 5 dietary treatments with 6 replicate floor pens of 75 birds each according to the above mentioned experimental design. Feed consumption and body weight gain of chicks in each replicate pen were recorded at the end of experiment.

2.2. Sample collections and analyses

At 17 days of age, chicks were individually weighed, and 24 chicks (four birds from each replicate pen) were chosen from each treatment based on average body weight following a 12-h fast. After the chicks were killed by cervical dislocation, liver and breast muscle samples were immediately collected and then frozen at –20°C for liver and breast muscle Se concentration analyses. All samples from four chicks in each floor pen were pooled into one sample in equal ratio before analysis. The concentrations of Se in Se sources, diets, liver and breast muscle samples were determined according to the method described by Tinggi (1999) by hydride generation atomic absorption spectrophotometer (AA6501, Shimadzu Ltd., Japan). Concentrations of crude protein, Ca and P in feed ingredient or diet samples were determined as described by AOAC (2003).

2.3. Statistical analyses

Data were analyzed by using the one-way analysis of variance (ANOVA) procedure of the SAS Institute (release 8.1; SAS Institute Inc., Cary, NC) and means were compared by the Tukey–Kramer multiple comparison test. P < 0.05 was considered to be statistically significant.

3. Results and discussion

There were no differences (P > 0.27) among the five treatments in average daily gain (ADG), average daily feed intake (ADFI) and feed conversion rate (FCR) of chicks during 7–17 days of age (Table 2), and the mortality of chicks in all groups was zero. This result might be explained by the short experimental duration and the Se concentration of basal diet (Echevarria et al. 1988). When a corn-soybean meal diet was used, the Se concentration in the basal diet (about 0.06 mg/kg) often met the requirement of chick growth, and there was no significant change in weight gain by Se supplement. Compared with the control chicks, chicks fed diets supplemented with Sodium selenite or Nano elemental Se had similar (P > 0.62) ADFI and ADG, however, chicks fed diets supplemented with Se yeast A or B tended to have higher (P > 0.20) ADG during 7–17 days of age. The overall growth performance results in the current study were in general agreement with the results of Yoon et al. (2007) and Perić et al. (2009). Payne and Southern (2005) also reported that organic Se did not affect growth performance, even though it increased tissue Se concentration compared with inorganic Se.

Table 2. Effect of Se source on growth performance of yellow broiler chicks during 7–17 days of age.^a,b

Item	ADG (g/day)	ADFI (g/day)	FCR (g/g)
Control	16.08 ± 0.11	27.58 ± 0.24	1.72 ± 0.01
Sodium selenite	16.13 ± 0.46	27.63 ± 0.53	1.72 ± 0.03
Nano red elemental Se	16.04 ± 0.25	27.25 ± 0.14	1.70 ± 0.03
Se yeast A	16.46 ± 0.25	27.88 ± 0.38	1.69 ± 0.02
Se yeast B	16.57 ± 0.11	28.03 ± 0.22	1.69 ± 0.01
ANOVA (p-value)	0.5220	0.5359	0.8538

ADG, Average Daily Gain; ADFI, Average Daily Feed Intake; FCR, Feed Conversion Rate.

^a Data represent the means of six replicate pens (n = 6).

^b Sodium selenite, Zhongxing Inc., Guangzhou, People's Republic of China; Nano elemental Se, Omega Biotech Co., Shanghai, People's Republic of China; Se yeast A, Alltech Inc., Nicholasville, USA; Se yeast B, Lallemand Inc., Montreal, Canada.

Tissue accumulation of a mineral is considered to be a sensitive criterion for mineral utilization (Ševčíková et al. 2006; Liao et al. 2012). In the current study, the Se source significantly affected (P < 0.05) liver and breast muscle Se concentrations of chicks (Table 3). Chicks fed the diet supplemented with Se yeast B had higher (P < 0.05) liver and breast muscle Se concentrations than those fed the diets supplemented with sodium selenite or Nano elemental Se. No differences (P > 0.66) were observed in liver and breast muscle Se concentrations among sodium selenite, Nano elemental Se and Se yeast A. However, chicks fed the diet supplemented with Se yeast A had numerically high values (P > 0.13) in liver and breast muscle Se concentrations compared with those fed the diets supplemented with sodium selenite or Nano elemental Se. There were no differences in liver Se and breast muscle Se concentrations between Nano elemental Se and sodium selenite treatments. The results of tissue Se retention agreed with those of Yoon et al. (2007) who reported that the Se concentrations were elevated in the liver, kidney, pancreas and breast muscle of broiler fed the diets supplemented with Se yeast compared with those of broiler fed the diets supplemented with sodium selenite. Wang and Xu (2008) also demonstrated that the Se contents in the liver and muscle were reflective of dietary Se supplementation, and Se retention was greater when Se yeast was supplemented compared with sodium selenite. In addition, the difference of tissue Se retention between Se yeast and sodium selenite or Nano elemental Se might be explained by the proposed metabolic pathway for Se from different Se sources (Zeng 2009). Once sodium selenite or Nano elemental Se are recognized as Se species, they are transformed to the common intermediate metabolite selenide, and then utilized for the synthesis of selenoproteins or excreted after being methylated stepwise. However, Se yeast contains a large amount of selenomethionine. When recognized as a Se species, it can be transformed to selenocysteine through the trans-selenation pathway and then lyased by β-lyase or directly by γ-lyase to selenide. In addition, selenomethionine can be utilized for the synthesis of proteins without the body distinguishing. So Se yeast might be easily utilized in the tissue than sodium selenite or Nano elemental Se (Suzuki 2005). Our result herein that there was no difference in tissue Se concentrations between Nano elemental Se and sodium selenite agreed with the result reported by Wang (2009), who also reported no significant difference was observed between sodium selenite and Nano-Se on growth performance and tissue Se distribution of avian broiler.

Table 3. Effect of Se source on tissue Se concentrations of yellow broiler chicks.^a,b,c

Item	Liver Se concentration (μg/g fresh tissue)	Breast muscle Se concentration (μg/g fresh tissue)
Control	0.744 ± 0.025 ^c	0.254 ± 0.010 ^c
Sodium selenite	0.860 ± 0.027 ^bc	0.280 ± 0.031 ^bc
Nano red elemental Se	0.863 ± 0.050 ^bc	0.295 ± 0.024 ^bc
Se yeast A	0.931 ± 0.058 ^ab	0.337 ± 0.020 ^b
Se yeast B	0.986 ± 0.052 ^a	0.436 ± 0.025 ^a
ANOVA (p-value)	0.0405	0.0002

^a Means with different letters within the same column differ (p < 0.05).

^b Data represent the means of six replicate pens (n = 6).

^c Sodium selenite, Zhongxing Inc., Guangzhou, People's Republic of China; Nano red elemental Se, Omega Biotech Co., Shanghai, People's Republic of China; Se yeast A, Alltech Inc., Nicholasville, USA; Se yeast B, Lallemand Inc., Montreal, Canada.

4. Conclusion

In summary, the results indicated that the new procedure used in the present experiment could detect the differences of tissue Se retention among Se sources for yellow broiler chicks fed a conventional corn-soybean meal basal diet, which could require a shorter experimental period and thus less cost. Based on the tissue Se retention estimated by the new procedure, Se yeast B was more effective than sodium selenite or Nano elemental Se.