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Brazilian Journal of Poultry Science

versão impressa ISSN 1516-635Xversão On-line ISSN 1806-9061

Braz. J. Poult. Sci. vol.21 no.4 Campinas  2019  Epub 20-Dez-2019

https://doi.org/10.1590/1806-9061-2018-0940 

ORIGINAL ARTICLE

Effects of Dietary Supplementation of Soy Isoflavones on the Performance and Egg Quality in Native Chinese Breeder Hens

ICollege of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, P.R. China.


ABSTRACT

To investigate the effects of soy isoflavones (ISF) on the laying performance of Xueshan breeder hens at different phases of the egg production cycle, 32 weeks (wks) old local Chinese breeder hens were assigned to two groups with three replicates (750 hens/replicate) for control and treatment groups. Then every group was divided into three sub-groups following 4, 12, and 20 wks administration of control or ISF diet. General Linear Model procedure was used (2× 3), and treatments were considered of two factors (diets and time) with different levels (control and ISF diets; 4, 12, and 20 wks of diet supply time). Basal diet with 3 mg/kg ISF was used. Performance, egg quality, organs relative weight and cholesterol level were measured at three time-points of 36, 44, and 52-wks of age old. The results showed that both diets and time significantly affected the production performance and physiological parameters. In details, ISF inclusion significantly (p=0.02) decreased average egg weight and average feed intake compared to control at 52-wks of age old, however, feed conversation ratio was not affected by ISF diet. Moreover, ISF diet caused to an increase hatching rate (p=0.01) at 36-wks old hens, an abnormal egg rate decrease (p=0.02) at 44-wks old, an increase in yolk color (p=0.035) and Haugh unit (p=0.039), and a decrease in low-density lipoprotein cholesterol level (p=0.03) at 52-wks of age old. ISF diet also increased spleen relative weight (p=0.041) and total antioxidant capacity compared to the control group. The results revealed that ISF inclusion exerted some benefits, thus it could be a potential feed additive for the breeder hens.

Keywords: Xueshan hens; egg quality; hatching traits; organs weight; cholesterol

INTRODUCTION

Feed additives of plant origin gain more interest among producers and nutritionists due to their safety, availability, their possible role in improving growth performance due to their antioxidant properties, and the lack of side effects for human and animals as well. Soy isoflavones (ISF) are natural synthesized phenolic compounds plants, which exist in two forms: conjugated or unconjugated (Kudou et al., 1991). They are commonly known as phytoestrogens because of their structural similarity to 17β-estradiol, and their capability to bind to estrogen receptor (ERs) with much more affinity to ERβ (Pilsakova et al., 2010). Soybean is considered to be the richest source of isoflavones.

During the last decade, scientists paid more attention to ISF and their compound (daidzein, genistein, and glycitein) due to their noticeable positive effects in human health (Ajdžanović et al., 2014). In addition, several studies showed that ISF had an antioxidant property (Jiang et al., 2007), could promote immune function (Zhang et al., 1997), prevented the breast cancer, lowered the risk of osteoporosis, decreased the plasma cholesterol level, and enhanced the antioxidative potential in humans and animals (Messina, 2010).

ISF has recently become popular as a dietary supplementation, especially for late laying production stage as a hormonal substitute to enhance the egg production rate. It is suggested that endogenous estrogen state, individual variation, duration and dose of phytoestrogen affects its act as an estrogen agonist or antagonist (Cassidy, 2003). Several studies reported that ISF improved growth and reproductive performance of the animals and their products (Yousef et al., 2004; Jiang et al., 2007; Shin et al., 2008). Furthermore, Shi et al. (2013) reported that feeding ISF to laying hens at 59 weeks of age showed an increase in egg production. Moreover, dietary ISF daidzein at 10, 20, and 30 mg/kg improved fertility and egg weight (Zhao et al., 2013). Also, a diet supplemented with ISF daidzein for Shaoxing duck breeder significantly enhanced the productive performance during late laying stage (Zhao et al., 2005), and the same improved laying performance, and eggshell quality were observed in post-peak laying stage of hens (Ni et al., 2007). Moreover, feeding quail in the late laying stage significantly improved egg quality and mineralization of the bone (Sahin et al., 2007).

Calcium (Ca) plays a vital role in bone and eggshell formation. ISF had been shown to decrease Ca concentration in osteoclasts (Kajiya et al., 2000), and consequently increase the available Ca for eggshell formation. Studies conducted by Zhao et al. (2005) and Sahin et al. (2007) confirmed that using ISF daidzein improved eggshell in chicken and quail, respectively.

It is extremely important to obtain a maximum number of eggs with optimal internal and external characteristics in breeder hens, especially for normal embryo development (Kontecka et al., 2012). On the other hand, broiler breeder diets modulate subsequent egg production rate (Peebles et al., 2000), embryo development and egg hatchability (Peebles et al., 2000).

Xueshan ‘snow mountain’ is a local hybrid meat type, it’s a favorite among consumers for its delicate, tender and delicious meat properties. Therefore, as far as we know, studies on the effect of ISF on performance and egg quality in domestic broiler breeder hens are limited. In general, the effects of ISF on poultry are contradictory. This study aimed to determine the effect of long term ISF supplementation on egg production, egg quality, fertility, hatchability, and cholesterol level at 36 wk, 44 wk, and 52 wk of age in local Chinese breeder hens.

MATERIALS AND METHODS

Birds and experimental treatments

Four thousand five hundred (4500), 32-week-old Chinese local Xueshan breeder hens were randomly divided into two groups: control and treatment groups. Each group consisted of three replicates and each replicate had 750 birds. Each group was divided into three sub-groups following 4, 12, and 20 wks administration of control or ISF diet. The experiment design followed General Linear Model procedure (2 × 3), and treatments were considered of two factors (diets and time) with different levels (control and ISF diets; 4, 12, and 20 wks of diet supply time).The birds in the control group were fed with a basal diet, while birds in the experimental group were fed with basal diet+ 3 mg/kg soy ISF from 28 to 52 wk of age. The trial lasted for 20 weeks. Every five days breeder hens were inseminated with 25µl of semen from cocks that received basal diets. Laying performance, egg quality, hatchability, and fertility were measured at 36 wk, 44 wk, and 52 wk, respectively. After the birds were slaughtered, organs (ovary, oviduct, heart, spleen, and kidney) were dissected and immediately weighed.

This trial was conducted in Jiangsu Lihua Animal Husbandry Stock Co. Ltd (Jiangsu, China). Soy isoflavone was obtained from Lihua Industrial Corporation (Changzhou, China). The birds were housed in wire cages, under 16 h light: 8 h dark cycle, and controlled temperature of 21ºC. All birds were fed with 130 g/bird/day, and free access to water. The composition and nutrient contents of the experimental diets are presented in Table 1. All animal handling protocols were approved by the Animal Care and Use Committee of Nanjing Agricultural University.

Table 1 Chemical composition and nutrient of the basal diet. 

Ingredients Composition (%)
Corn 64.1
Soybean meal 19.0
Fish meal 2.0
Limestone 8.6
Bran 3.7
Sodium chloride 0.3
Dicalcium phosphate 1.3
Premix1 1.0
Total 100.0
Calculated composition2
ME (MJ/kg) 11.17
CP3 (%) 16.16
Cys +Met 0.59
Lys (%) 0.92
Calcium (%) 3.56
AP (%) 0.38

1 Provided per kilogram of diet: vitamin A, 6,000 IU; vitamin D3, 3,630 IU; vitamin E, 22 IU; vitamin K 2.2 mg; vitamin B1 2.2 mg; vitamin B2 8.25 mg; vitamin B6 6.6 mg; biotin 0.55 mg; folic acid 1.1 mg; vitamin B12 0.011 mg; vitamin B3 20 mg; copper, 15 mg; iron, 70 mg; zinc, 75 mg; manganese, 50 mg; iodine, 0.55 mg; selenium, 0.36 mg.

2ME, metabolic energy; CP, crude protein; Cys, cysteine; Met, methionine; Lys, lysine; AP, available phosphorus.

Performance and egg quality

Eggs were collected twice a day, and egg production rate was calculated from the total number of eggs divided by the total number of days. Feed intake was recorded on a replicate basis at weekly intervals. Egg mass was calculated as egg production rate × average egg weight. Feed conversion ratio was calculated as a gram of feed consumed divided by a gram of egg produced.

For egg quality, six eggs were chosen randomly at the age of 36 wk, 44 wk, and 52 wk respectively and analyzed for internal and external characteristics. The length and width were measured using Digital Caliper® (MNT-150. Shanghai, China). The shape index was calculated (width/length × 100). Egg Multi-tester (EMT-5200, Crescent Science and Technology Co. Ltd. China) was used to automatically measure egg weight, albumen height, Haugh unit (HU), and yolk color. The device uses 1 throughout of 15 scales color index to distinguish the yolk color density, ultrasound sensors to measure albumen height. The yolk was separated from the albumen and then weighed. The eggshell was weighed with the shell membrane. The ratio of yolk to albumen was calculated.

Fertility and hatchability

Eggs for hatching were collected at 36 wk, 44wk, and 52 wk and stored at 18 ºC before incubated. The abnormal egg rate was calculated as number of abnormal eggs/number of laying eggs%, soft egg rate was determined as number of soft eggs/number of laying eggs%. The thermal condition for the incubator was 37 ºC and 60% relative humidity. Incubated eggs were candled on the 7th day of incubation to determine the number of infertile eggs. The Fertility % was calculated as number of fertile egg × 100/number of eggs set. On day 21 the hatchability of fertile eggs was calculated.

Sample collection

Hens were weighed individually at 36, 44, and 52 wks of age to evaluate body weight. Eight birds from each time-period were slaughtered to collect blood samples, which immediately were centrifuged (3,000 × g at 4 ºC), and the isolated serum was stored at −20 ºC until further analysis. Organs (ovary, oviduct, heart, spleen, liver, and kidney) were dissected and weighed.

Cholesterol assay

Serum samples were examined for total cholesterol (TCHO), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), and total antioxidant capacity (T-AOC) using a commercial kit according to manufacturer’s instructions (Jian Cheng Bioengineering Institute, Nanjing, China).

Statistical analysis

All data were analyzed with SPSS software (SPSS, Inc., Chicago, IL., Version 20.0) using the General Linear Model procedure, repeated measurement ANOVA procedure was used (2 × 3) to analyze the statistical difference between time-points, and t-test was used for difference within time-point. Differences between means were tested using Tukey’s Multiple Comparison Range Test. All data were presented as means ± standard error and probability values less than 0.05 were considered statistically significant. Considering the statistical model as follow:

Yijk=mv+ai+bj+(ab)ij+eijk

Where,

Y ijk = Dependent variable.

μ v = General mean.

α i = Effect of the diet factor (i = 2).

β j = Effect of the weeks (j = 3).

(αβ) ij = Interaction between 2 factors.

ε ijk = Normally distributed random experimental error on repeated measures with variance.

Diets and supply time were 2 factors. Control diet and ISF diet are 2 diets, and the ISF supplementation period of 4, 12 and 20 wks were considered as 3 time points.

RESULTS

Performance

After feeding ISF for 20 weeks, the effects of group factor, week’s factor and the interaction between group× weeks were analyzed. No significant change was observed in body weight between the control group and ISF supplemented group within the time-point. The ISF group at 44 wks showed a heavier body weight (p<0.001) than 36 and 52 wk old hens. As shown in Table 2, the egg production rate and average egg mass showed no statistical differences between the control and treatment group within the time interval. A significant reduction in both egg production rate (p=0.018) and egg mass were observed with age increase within time interval investigated. At 52 wk of age, the ISF significantly decreased the egg weight in comparison to the control group (p=0.02). Among the control groups, at different weeks, the 52 wk old hens had a heavier egg weight than at 36 and 44 wks (p=0.01). A significant interaction between group × weeks was observed in average egg weight (p=0.018) and average daily feed intake (p=0.0001).

Table 2 The main effect (mean±SE) of soy isoflavones supplementation on egg production rate, average egg weight, average egg mass, feed conversion ratio and average daily feed intake of Chinese local broiler breeder hens at 36, 44, and 52 weeks of age. 

Weeks of age Statistical significance
Group 36 44 52 Group Weeks Group × Weeks
Body weight (kg)
Control 2.45 ± 0.01 2.75 ± 0.02 2.64 ± 0.05 NS p<0.001 NS
ISF 2.34 ± 0.09c 2.74 ± 0.04a 2.56 ± 0.03b
Egg production rate (%)
Control 77.42 ± 0.27a 69.85 ± 0.29b 61.49 ± 0.23c NS p<0.001 NS
ISF 76.71 ± 0.38a 69.29 ± 0.36b 61.98 ± 0.45c
Average egg weight (g)
Control 52.76 ± 1.28b 50.66 ± 0.35b 57.73 ± 0.78a p<0.05 p<0.001 p<0.05
ISF 49.58 ± 0.85 50.88 ± 0.73 52.76 ± 1.28*
Average egg mass (g/bird/d)
Control 39.69 ± 1.24 35.75 ± 0.39 35.18 ± 0.34 NS p<0.001 NS
ISF 38.72 ± 0.98 35.06 ± 0.41 32.99 ± 0.59
Average daily feed intake (g/bird/d)
Control 110 ± 0.05a 101 ± 0.11b 101 ± 0.10bc p<0.05 p<0.001 p<0.001
ISF 110 ± 0.23b 102 ± 0.11a* 99 ± 0.02c*
Feed conversion ratio (kg /egg mass)
Control 2.80 ± 0.09 2.83 ± 0.03 2.87 ± 0.03 NS NS NS
ISF 2.85 ± 0.07 2.90 ± 0.03 2.98 ± 0.07

The number in each group was n=8. SE, standard error; ISF, soy isoflavones; NS, no significant difference.

*Means significantly different (p<0.05) in the same column.

a-cDifferent superscripts in the same row mean differ significantly (p<0.05).

Fertility and hatchability

As shown in Table 3, no significant difference was observed between the control and treatment groups at 36, 44, and 52 wks of age in soft egg rate. The hatching rate improved significantly (p=0.01) in ISF supplemented group at 36 wks of age compared with that recorded in the control group. However, a significant decrease was observed due to the increase in age (p=0.029). The ISF decreased abnormal egg rate in 36 wks of age compared to the untreated group (p=0.02). No significant difference was observed between control and treatment groups at 36, 44, and 52 wks of age in fertility rate. The interaction between treatment and duration has a significant effect on hatchability rate and abnormal egg rate (p=0.001).

Table 3 The main effect (mean±SE) of soybean isoflavones on hatching rate, abnormal egg rate, and soft egg rate of Chinese local broiler breeder hens at 36, 44, and 52 weeks of age. 

Weeks of age Statistical significance
Group 36 44 52 Group Weeks Group × Weeks
Hatching rate (%)
Control 97.65 ± 0.12b 97.93 ± 0.0ab 98.12 ± 0.09a p<0.05 p<0.05 p<0.001
ISF 98.39 ± 0.11a* 97.78 ± 0.12b 97.65 ± 0.14b
Abnormal egg rate (%)
Control 1.25 ± 0.13a 0.68 ± 0.05bc 0.79 ± 0.00b p<0.05 p<0.05 p<0.001
ISF 0.66 ± 0.11* 0.78 ± 0.04 0.83 ± 0.06
Soft egg rate (%)
Control 1.22 ± 0.04 1.36 ± 0.05 1.31 ± 0.00 NS p<0.05 NS
ISF 1.16 ± 0.06 1.52 ± 0.11 1.45 ± 0.09
Fertility (%)
Control 94.50 ± 0.43 93.50 ± 0.43 92.33 ± 0.33 NS p<0.001 NS
ISF 94.33 ± 0.33 93.83 ± 0.48 92.00 ± 0.45

The number in each group was n=8; SE, standard error; ISF, soy isoflavones; NS, no significant difference.

*Means significantly different (p<0.05) in the same column.

a-cDifferent superscripts in the same row mean differ significantly (p<0.05).

Egg quality

The egg quality parameters were shown in Table 4. The ISF significantly increased the egg index percentage at 36 (p=0.036) and 52 wks of age (p=0.02) respectively, but not at 44 wks. The ISF treated group had lower HU compared to the control group at 36 wks of age (p=0.032), while ISF supplementation significantly increased HU compared with the control group at 52 wks of age (p=0.039). At the time-points of 36 wks of age, the control group showed heavier shell weight than at peak period of the treated group. Regarding the internal egg quality, the eggs from ISF at 44 wks of age showed higher yolk color (p=0.035) than the control group, while the eggs from 52 wks of age had lower yolk color than the control group (p=0.01). At late laying period, the treated group has a significant reduction (p=0.017) in albumen weight compared with that recorded from the control group at the same age. A significant interaction between treatment × weeks was observed in index percentage, HU (p=0.032), yolk color (p=0.018), albumen height (p=0.02) and yolk weight (p=0.002).

Table 4 The main effect (mean±SE) of supplemented soy isoflavones on some egg quality parameters of Chinese local broiler breeder hens at 36, 44, and 52 weeks of age. 

Weeks of age Statistical significance
Group 36 44 52 Group Weeks Group × Weeks
Egg shape Index (%)
Control 78.59 ± 0.53 76.97 ± 1.53 78.66 ± 1.05 p<0.05 NS p<0.05
ISF 75.34 ± 1.03* 77.88 ± 1.52 75.40 ± 0.81*
Haugh unit
Control 78.95 ± 1.83a 62.98 ± 3.57b 56.29 ± 1.89bc p<0.05 p<0.001 p<0.05
ISF 72.53 ± 1.80* 63.80 ± 3.50 65.18 ± 3.23*
Yolk color
Control 8.24 ± 0.16b 9.00 ± 0.14a 9.2 ± 0.21a p<0.05 p<0.001 p<0.05
ISF 8.31 ± 0.09c 9.68 ± 0.58a* 8.65 ± 0.21b*
Yolk weight (g)
Control 16.02 ± 0.22b 15.10 ± 0.68bc 20.80 ± 0.41a NS p<0.001 p<0.01
ISF 15.41 ± 0.20c 17.41 ± 0.59b* 20.14 ± 0.58a
Yolk ratio (%)
Control 0.31 ± 0.01b 0.30 ± 0.01bc 0.36 ± 0.01a p<0.05 p<0.001 NS
ISF 0.31 ± 0.00c 0.34 ± 0.01b 0.37 ± 0.00a
Albumen height (mm)
Control 5.54 ± 0.42a 3.62 ± 0.21bc 4.30 ± 0.32b NS p<0.01 p<0.05
ISF 4.32 ± 0.39 3.86 ± 0.37 4.12 ± 0.28
Shell weight (g)
Control 5.33 ± 0.11 5.24 ± 0.05 5.49 ± 0.07 NS p<0.01 NS
ISF 4.89 ± 0.07b* 5.23 ± 0.14ab 5.57 ± 0.19a
Albumen weight (g)
Control 30.83 ± 0.88 28.90 ± 0.58 31.49 ± 0.64 p<0.05 p<0.05 NS
ISF 29.12 ± 0.68 27.07 ± 0.71 27.78 ± 1.13*
Albumen ratio (%)
Control 0.59 ± 0.01a 0.58 ± 0.01a 0.54 ± 0.01b p<0.05 p<0.001 NS
ISF 0.59 ± 0.01a 0.55 ± 0.00b* 0.52 ± 0.01c

The number in each group was n=8. SE, standard error; ISF, soy isoflavones; NS, no significant difference.

*Means significantly different (p<0.05) in the same column.

a-cDifferent superscripts in the same row mean differ significantly (p<0.05).

Organ relative weight

The relative hens’ organs weights are shown in Table 5. A significant increase was observed in relative liver weight between the control groups at 44 wks of age compared 52 wks of age (p=0.045) respectively. In addition, ISF inclusion has a significant increase in spleen relative weight compared to the control group at 52 wks of age. No significant interaction between ISF supplementation and time-point was observed throughout the experimental duration.

Table 5 The main effect (mean±SE) of soy isoflavones supplementation on relative organs weight of Chinese local broiler breeder hens at 36, 44, and 52 weeks of age. 

Weeks of age Statistical significance
Group 36 44 52 Group Weeks Group × Weeks
Relative heart (%)
Control 0.41 ± 0.00a 0.47 ± 0.03a 0.33 ± 0.01b NS NS NS
ISF 0.42 ± 0.02 0.39 ± 0.03 0.34 ± 0.02
Relative liver (%)
Control 2.12 ± 0.13 1.98 ± 0.14 1.78 ± 0.05 NS p<0 .05 NS
ISF 2.01 ± 0.07ab 2.13 ± 0.04a 1.85 ± 0.03b
Relative spleen (%)
Control 0.09 ± 0.00a 0.08 ±0.00ab 0.07 ±.00b p<0 .05 p<0.01 NS
ISF 0.09 ± 0.00a 0.07 ±0.00b 0.09 ± 0.00a*
Relative ovary (%)
Control 1.48 ± 0.06 1.92 ± 0.17 1.96 ± 0.11 NS NS NS
ISF 1.89 ± 0.11 1.80 ± 0.11 2.07 ± 0.21
Relative oviduct (%)
Control 2.08 ± 0.08 2.06 ± 0.09 2.22 ± 0.13 NS NS NS
ISF 2.23 ± 0.10 2.08 ± 0.17 2.13 ± 0.14
Oviduct length (cm)
Control 65.33 ± 2.17 59.88 ± 2.41 61.70 ± 1.28 NS NS NS
ISF 62.67 ± 2.53 62.17 ± 2.39 59.08 ± 0.84

The number in each group was n=8; SE, standard error; ISF, soy isoflavones; NS, no significant difference.

*Means significantly different (p<0.05) in the same column.

a-cDifferent superscripts in the same row mean differ significantly (p<0.05).

Serum concentrations of some metabolites and antioxidant parameters

As shown in Table 6, ISF dietary inclusion significantly decreased the serum level of TCHO at 52 wks compared to the control group. Among treated weeks groups, TCHO was higher in 44 and 52 wks compared to 36 wks. The interaction between treatment and time-point was observed (p=0.0027). The ISF supplementation reduced serum level of LDL-C significantly (p=0.05) in the late laying period of treated hens. ISF supplementation significantly elevated the T-AOC in all time-point compared to control groups. No significant interaction effect was observed between group and weeks in LDL-C, HDL-C, TG, and T-AOC.

Table 6 The main effect (mean±SE) of soybean isoflavones supplementation on serum concentration of some metabolites and antioxidant parameters of Chinese local broiler breeder hens at 36, 44, and 52 weeks of age. 

Weeks of age Statistical significance
Group 36 44 52 Group Weeks Group × Weeks
TCHO (mmol/l)
Control 7.40 ± 0.50a 6.46 ± 0.41b 8.26 ± 0.43a p<0.05 p<0.05 p<0.05
ISF 5.59 ± 0.67b 7.72 ± 0.52a 6.54 ± 0.34a*
LDL-C (mmol/l)
Control 6.33 ± 1.24a 4.26 ± 0.90b 9.58 ± 1.28a p<0.01 p<0.05 NS
ISF 5.48 ± 0.43 2.99 ± 0.99 5.33 ± 0.82*
HDL-C (mmol/l)
Control 0.47 ± 0.13b 0.41 ± 0.06b 1.30 ± 0.25a NS p<0.05 NS
ISF 0.87 ± 0.31 0.45 ± 0.02 0.66 ± 0.21
TG (mmol/l)
Control 19.27 ± 1.66 20.10 ± 0.40 22.89 ± 2.16 NS NS NS
ISF 19.19 ± 1.69 20.36 ± 1.50 23.98 ± 1.59
T-AOC (U/ml)
Control 4.36 ± 0.24a 1.85 ± 0.37b 2.07 ± 0.23b p<0.01 p<0.001 NS
ISF 6.09 ± 0.27a* 3.64 ± 0.46b* 3.43 ± 0.16b*

The number in each group was n=8; SE, standard error; TCHO, total cholesterol; LDL-C, low-density lipoprotein cholesterol; HDL-C, high -density lipoprotein cholesterol; TG, triglyceride; T-AOC, total anti-oxidative capability; ISF, soy isoflavones; NS, no significant difference.

*Means significantly different (p<0.05) in the same column.

a-cDifferent superscripts in the same row mean differ significantly (p<0.05).

DISCUSSION

Phytoestrogens; as soybean ISF (daidzein, genistein, glycitein), was used as a feed additive for the biological functions. They exert controversial results in animal studies. However, the effect depended on several factors, including the dose, the form of ISF, duration of ISF intake and the breed or species. Our study has demonstrated the effects of 3 mg/kg ISF dose on performance, egg quality, hatchability, and some oxidative status in Chinese Xueshan local broiler breeder hens at different stages of its production cycle, peak, post-peak and terminal stage. In our study, no significant changes were noted regarding breeder hen’s body weight or organs relative weight throughout the experimental period. Except for spleen relative weight which was significantly heavier at late laying period of treated group; this result may indicate that ISF might help in hen’s immunity, which was in accordance with the dietary inclusion of 1-5% ISF for Japanese quail in the study by Wilhelmset al. (2006), and Goliomytis et al. (2014) who reported that phytoestrogen quercetin did not influence growth performance of broiler. In disagreement with Jiang et al. (2007) who reported that dietary supplementation with 10, 20 mg/kg ISF significantly increased final body weight, daily weight gain and average feed intake in the male broiler. The reason for this may be due to restricted feeding program used and dosages. The experimental breeder hens started laying eggs at 20 wks of age. The influence of broiler breeder feeds on subsequent egg production performance (Peebles et al., 2000), and embryo development and egg hatchability (Peebles et al., 2000), have been well documented. In the present trial, age-related decrease in egg production was observed in both groups. Egg production rate, egg mass, and feed conversion ratio were not influenced due to ISF supplementation throughout the experimental period. It was consistent with the previous results reported by Lu et al. (2017) using high ISF dosage in laying diet, and in contrast with several studies (Zhao et al., 2005; Ni et al., 2007; Gu et al., 2013; Khalaji et al., 2013; Shi et al., 2013), this might be due to the breed and ISF dosage. However, a significant reduction in the average daily feed intake was recorded in a late laying stage; consequently; a reduction in the average egg weight was observed at the same time-point. In opposite with results reported by Zhao et al. (2005), and Zhao et al. (2013) who used ISF daidzein to feed duck and geese respectively.

Many factors can affect the hatchability rate, such as different treatment during storage and incubation. However, it is suggested that ISF influence hatchability and fertility by improving eggshell quality, especially in older breeder hens. In this experiment, we found that ISF reduced the abnormal egg rate and hatchability rate at peak laying stage and significantly lowered the hatchability rate in the late production stage. In agreement with Zhao et al. (2013), who supplemented ISF daidzein to the geese diet, and in contrast with, (Zhao et al., 2004; Zhao et al., 2005). However, these conflicting results might be due to the phytoestrogen source used in the other study, dosage, duration, and the species.

Age factor has a direct impact on some internal and external egg quality parameters, and it is well documented that egg weight increased with hens’ age, leading to heavier shell, yolk and albumen weights. However, Zita et al. (2009)_ENREF_23 reported that proportional shell and albumen weight decrease with age, while the yolk proportion weight increased with age. Also, De Matos (2008)_ENREF_36 reported that Ca provides and support the structural strength of bones and eggshell. Moreover, a study by Messina et al.(2004) showed that higher consumption of isoflavones increased bone density, and there is a tight link between Ca and ISF (Fonseca & Ward, 2004). Subsequently, the availability of Ca for eggshell formation increased due to the ability of ISF to decrease intracellular Ca concentration in osteoclasts (Kajiya et al., 2000). In the present study, ISF supplementation enhanced egg quality parameters as follows: yolk weight, HU, the percentage of egg index, shell weight, and yolk ratio, inconsistent with previous results (Sahin et al., 2007; Akdemir & Sahin, 2009; Mattioli et al., 2017). In contrast, Zhao et al. (2005) claimed that feeding ISF daidzein increased albumen weight and decreased yolk weight in Shaoxing duck.

ISF has hypocholesterolemic effects in humans and in animals (Carroll & Kurowska, 1995; Yang et al., 2012). In the present study, ISF treatment was lowering the serum level of TCHO and LDL-C during late laying period (52 wks of age), but without a change in HDL-C and TG, this was in agreement with a previous study (Taku et al., 2007). Also, no change was observed in TCHO and TG serum level when a high level of ISF daidzein was used (Lu et al., 2017), while Torres et al. (2006) noticed a redution in the serum level concentration of Cholesterol and TG in rats. Potter et al. (1998) suggested that ISF might have an estrogenic effect in the lowering of LDL and elevation of HDL concentration, which might be result from stimulation of bile acid excretion and increased liver LDL cholesterol receptor expression (Anderson et al., 1995).

The T-AOC is a useful tool to measure the redox status since it considers the cumulative action of all antioxidants (Ghiselli et al., 2000). ISF exhibit their antioxidant activity by donating a hydrogen atom from the hydroxyl group (Sierens et al., 2002). In this trail, ISF treatment showed an elevation in serum T-AOC throughout the experiment, which was in agreement with previous studies (Jiang et al., 2007; Liu et al., 2009; Kamboh & Zhu, 2013).

CONCLUSION

In conclusion, dietary ISF supplementation for 20 weeks improved yolk weight and yolk color at post-peak and HU at the terminal stage with LDL-C reduction in the same period of Xueshan breeder hens, which indicated that the egg quality was improved by ISF diet. The body weight was not affected by ISF diet, however, ISF administration elevated T-AOC in the serum throughout the breeder laying cycle and increased relative spleen weight, which suggest that the antioxidant and immunity conditions might be improved by ISF diet. Thus, ISF could be used as a potential alternative of a synthetic feed additive to enhance healthy status for broiler breeder hens.

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Received: January 14, 2019; Accepted: June 27, 2019

Corresponding author e-mail address Chunmei Li College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, P.R. China. Phone: +86-025-84395971 Email:chunmeili@njau.edu.cn

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