Effect of selenium and vitamin E supplementation on reproductive indices and biochemical metabolites in Raieni goats

Abstract

The aim of this study was to investigate the effect of selenium (Se) and vitamin (vit) E supplementation on reproductive indices and biochemical metabolites in Raieni goats. Ninety adult Raieni goats, weighing 43 ± 2.5 kg and with a body condition score of 3.5 ± 0.1, were randomly allocated into nine groups which entered into an experiment with 3 × 3 factorial design. The experimental diets consist of three levels of se (0.0, 0.3 and 0.5 mg/kg of feed) and three levels of vit E (0.0, 20 and 50 mg/kg of feed). At the end of the experiment, blood samples were collected from the jugular vein of all goats into 10-ml vacuum tubes (venoject). Serum was recovered by centrifugation (10 m at 3000 rpm) and stored at –20°C until assayed for the concentration of biochemical metabolites (glucose, cholesterol, triglycerides, low-density lipoprotein (LDL), high-density lipoprotein (HDL), total proteins, albumin and T3 and T4). The results of this experiment revealed that supplementation of diets with Se or vit E had no significant effect on biochemical metabolites or reproductive traits. However, the interactive effect of Se and vit E on reproductive indices was significant (P < 0.05), with goats fed diets containing 0.5 mg/kg Se and 20 mg/kg vit E, giving birth to heavier kids compared to those which received the other dietary treatments.

Keywords:

• selenium
• vitamin E
• reproductive indices
• Raieni goat

1. Introduction

Recently research has shown that minerals nutrition has an important role on goat performance, and the relationship between nutrition and physiology has played a key role in the recent years (Argüello 2011). Selenium (Se) is necessary for growth and fertility in animals and also for the prevention of a variety of disease conditions, which show a variable response to vitamin (vit) E for reasons which are becoming clearer as more is known about the functional forms of Se and their localization (Macpherson 1994). Se, as an anti-oxidant, works in conjunction with vit E in preventing and in repairing cellular damage in an animal’s body, and deficiency of Se or vit E can also impair immune response (Gutteridge & Halliwell 1994). Se has biological functions associated with thyroxine, a thyroid hormone regulating metabolism, reproduction, circulation and muscle function. Se also protects the animal’s body from heavy metals by forming complexes to render them harmless (Pavlata et al. 2004; Kachuee et al. 2013). Se is easily transferred through the placenta and milk; therefore, a doe’s Se status will directly affect the health and thriftiness of her kids (Kachuee et al. 2013). Marginal Se deficiencies can result in impaired fertility, silent heats, cystic ovaries and the birth of unthrifty kids with poor immunity (Nix 2002). Se is highly toxic if excess amounts are consumed. Unfortunately, the amount of se required is very close to the toxicity level, thus great care must be taken when supplementing Se. The maximum level of se that can be legally fed to goats is 0.7 mg per head per day or 0.3 ppm in the total ration (dry matter basis; Nix 2002).

Se deficiency plays a role in numerous economically important livestock diseases, problems that include impaired fertility, abortion, retained placenta and neonatal weakness (McDowell et al. 1996). Supplementation of the diet with Se improves daily weight gain of lambs (Gabryszuk & Klewiec 2002) and reproductive performance in ewes. Vit E may prevent peroxidation in the susceptible subcellular membrane (Koyuncu & Yerlikaya 2007) and prevent oxidative damage to sensitive membrane lipids by decreasing hydrogen peroxide formation (Chow 2001), thus maintaining membrane integrity and reducing oxidative stress (Hogan et al. 1993; Kachuee et al. 2013). However, on the basis of current knowledge, there is limited information about effects of Se and vit E on reproductive indices and biochemical metabolites of Raieni goats. Therefore, the aim of the present study was to evaluate the effects of Se and/or vit E supplementation on reproductive performance of Raieni goats, and on growth of their kids, with emphasis on some biochemical and physiological parameters.

2. Material and methods

2.1. Location, animals and blood collection

This experiment was conducted at the Raieni Goat Breeding Station in Baft city, which is located in the south-east of Kerman province, Iran (2250 metres above the sealevel, 92° 17 N latitude and 56° 36 E longitude, and 220 mm annual rainfall), from July to September 2012. The average ambient temperature during the experiment was 25°C–30°C. Ninety adult Raieni goats, weighing 43 ± 2.5 kg and with a body condition score of 3.5 ± 0.1, were randomly allocated into nine groups which entered into an experiment with 3 × 3 factorial design. All goats were submitted to examination for general clinical and sanitary condition and fed a ration which contained alfalfa hay, barley grain and wheat bran according to the recommendations of National Research Council (Table 1). The experimental diets were prepared by an addition of different levels of Se (0.0, 0.3 and 0.5 mg/kg of feed) and vit E (0.0, 20 and 50 mg/kg of feed) to the basal ration. At the end of experiment, blood samples were collected from the jugular vein of all goats into 10-ml vacuum tubes (venoject). Serum was recovered by centrifugation (10 m at 3000 rpm) and stored at –20°C until assayed for the concentration of biochemical metabolites (glucose, cholesterol, triglycerides (TG), low density lipoprotein (LDL), high-density lipoprotein (HDL), total proteins, albumin and T3 and T4).

Table 1. Ingredients and composition of the ration.

Items	Percentage (%)
Alfalfa hay	50
Barley grain	10
Wheat bran	30
Soybean meal	7
Limestone	2
Salt	1
Total	100

2.2. Biochemical analysis of the serum

The concentrations of glucose, cholesterol, TGs, LDL, HDL, total proteins and albumin were measured using commercially available kits. The determination of metabolite levels in blood serum was estimated by a commercial clinical photometric analyser (Model BT-3000). Standard commercial kits were used for analysis, and procedures were adopted as recommended by the manufacturer of kits. After processing samples and standards provided with the kits, absorbance of the standard and the samples was determined and the concentrations of respective metabolites in samples were computed, using the formula: concentration of a metabolite = absorbance of sample divided by absorbance of standard and multiplied by standard concentration.

2.3. Statistical analysis

Data were subjected to analysis of variance (ANOVA) using the General Linear Model (GLM) procedure of Minitab. Before analysis, the univariate test was used to assess the normality of all data (Minitab 2004). Duncan’s test was used to detect differences during the experimental periods.

3. Results and discussion

The effects of Se on serum biochemical metabolites of Raieni goats are presented in Table 2. The effect of supplementation of diets with different levels of Se on glucose was not significant (P > 0.05). The blood cholesterol was not affected by an addition of Se. The Se supplementation had no significant effect on blood TG. Although addition of different levels of Se on LDL was not significant, supplementation of 0.5 mg/kg se to diet tended to (P = 0.082) increase blood HDL compared to the other dietary treatments. The effect of different levels of Se on albumin and total protein was not significant (P > 0.05). Shahat and Abdel Monem (2011) reported that all groups of Baladi ewes which received se alone had significantly lower total serum protein, albumin and globulin, whereas those fed additional antioxidants (vit E/Se) had significantly improved levels of total serum protein and globulin. A similar finding was reported in buffaloes (Helal et al. 2009). The values of total serum protein, albumin herein, were within the physiological levels previously reported (Kaneko 1989). However, other research showed no significant effect of vit E and Se on the serum concentrations of total protein and albumin in sheep (Hamam and Abou-Zeina 2007). Vit E and Se together have a greater beneficial effect on immunity than Se administration alone. The serum T3 and T4 were not significantly (P > 0.05) affected by Se supplementation. Shahat and Abdel Monem (2011) reported that vit E plus Se-supplemented groups had higher serum concentrations of T, and many other investigators have found the same results and confirmed the importance of Se for thyroid hormone metabolism in ewes Abou-Zeina and Hamam (2002) and in cattle (Arthur et al. 1993). Se is needed for hepatic conversion of T to 3, 3, 5- triiodothyronine, and Type I iodothyronine deiodinase has been identified as a selenoscysteine containing enzyme which catalyses deiodination of T to biologically active thyroid hormone T. Research (El-Sisy et al. 2008) has shown that Se supplementation of the diet of Baladi male goats resulted in a significant decrease in T4 concentration, concomitant with an increase in T3 concentration. Sivakumar et al. (2010) reported that free T3 and T4 of goats increased in antioxidant (Se and vit E) treatment groups.

Table 2. Effect of different levels of se on serum biochemical metabolites of Raieni goats (n = 10 goats per treatment).

Se (mg/kg)	0.0	0.3	0.5	SE	P-value
Biochemical metabolites
Glucose (mg/dl)	20.8	24.1	20.4	1.73	0.28
Cholesterol (mg/dl)	56.7	57.1	61	3.6	0.652
TG (mg/dl)	25	24.9	28.2	2.26	0.509
LDL (mg/dl)	29.1	28.9	31	1.79	0.663
HDL (mg/dl)	28	28.2	32.8	1.59	0.082
Albumin (g/dl)	3.8	4	4	0.13	0.393
Protein (g/dl)	6.8	7.2	7.1	0.23	0.495
T3 (ng/ml)	2.3	1.7	1.8	0.18	0.103
T4 (µg/dl)	11.2	10.5	10.4	0.56	0.633

The effect of different levels of vit E on biochemical metabolites is illustrated in Table 3. Supplementation of diets with different levels of vit E had no significant effect on any blood metabolites measured in this experiment. However, vit E supplementation at the level of 50 mg/kg tended to (P = 0.132) increased blood glucose. The addition of 20mg/kg vit E tended to (P = 0.067) increase blood cholesterol compared to the other dietary treatments. Vit E supplementation had no significant effect (P > 0.05) on blood TG. Adding vit E at the level of 20mg/kg tended (P = 0.127 and 0.129, respectively) to increase LDL and HDL compared to other dietary treatments. Supplementation of diets with different levels of vit E had no significant effect (P > 0.05) on albumin or total protein. Supplementation of diet with different levels of Vit E had no significant effect on serum T3 and T4. Our findings concur with the reports of El-Shahat and Abdel Monen (2011) that supplementation of ewe diets with vit E had no significant effect on any blood parameters.

Table 3. Effect of different levels of vit E on serum biochemical metabolites of Raieni goats (n = 10 goats per treatment).

Vit E (mg/kg)	0.0	20	50	SE	P-value
Biochemical metabolites
Glucose (mg/dl)	21.7	19.2	24.4	1.73	0.132
Cholesterol (mg/dl)	51.7	64.4	58.7	3.6	0.067
TG (mg/dl)	27.6	27.4	23.1	2.26	0.308
LDL (mg/dl)	27	32.4	29.6	1.79	0.127
HDL (mg/dl)	27.4	32.2	29.3	1.58	0.129
Albumin (g/dl)	4	3.8	4.1	0.13	0.411
Protein (g/dl)	7.1	6.9	7.1	0.27	0.794
T3 (ng/ml)	2.3	1.7	1.8	0.18	0.161
T4 (μg/dl)	10.9	10.6	10.5	0.59	0.845

The interactive effects of Se and vit E on serum biochemical metabolites are shown in Table 4. As can be seen from Table 4, the interactive effect of Se and vit E on blood parameters was not significant (P > 0.05). However, there is a tendency for the interactive effect (P = 0.084) of Se and vit E supplementation on blood glucose, and goats fed a diet containing 0.5mg/kg Se and 20 mg/kg vit E had higher blood glucose compared to the other dietary treatments.

Table 4. Interactive effect of different levels of Se and vit E on serum blood metabolites of Raieni goats.

Se (mg/kg)	0.0	0.0	0.0	0.3	0.3	0.3	0.5	0.5	0.5
Vit E (mg/kg)	0.0	20	50	0.0	20	50	0.0	20	50	SE	P-value
Biochemical metabolites
Glucose (mg/dl)	24.3	22.7	18.0	15.0	19.3	23.3	23.0	30.3	20.0	3.00	0.084
Cholesterol (mg/dl)	48.0	52.3	54.7	58.0	58.7	76.7	64.0	60.3	51.7	6.24	0.157
TG (mg/dl)	21.3	31.3	30.0	27.0	22.3	33.0	26.7	21.0	21.7	3.91	0.162
LDL (mg/dl)	24.3	26.7	29.0	29.7	29.3	38.3	33.3	29.7	25.7	3.10	0.109
HDL (mg/dl)	24.3	27.0	31.0	29.3	28.3	39.0	30.3	29.3	28.3	2.75	0.202
Albumin (g/dl)	3.8	4.2	3.9	3.7	3.9	3.9	3.9	4.1	4.23	0.22	0.924
Protein (g/dl)	6.9	7.3	7.0	6.1	7.4	7.3	7.4	6.9	7.1	0.39	0.256
T3 (ng/ml)	2.7	2.1	1.9	2.1	1.4	1.8	2.0	1.7	1.7	0.32	0.753
T4(µg/dl)	12.4	10.8	9.7	10.6	10.1	11.1	10.5	10.7	10.3	1.04	0.599

The effect of different dietary levels of Se on reproductive indices is presented in Table 5. The effect of Se supplementation was not significant (P > 0.05) for any reproductive parameters measured in this experiment. Our results are in agreement with those of El-Shahat and Abdel Monem (2011 who reported that addition of different levels of Se had no significant effect on birth and third month weight of lambs. It cannot be denied that se supplementation in se-deficient diets is important, as this element plays an important role in many other physiological processes in goats (Ganabadi et al. 2010). Se directly affects reproductive events in sheep and in goats, such as expression of estrus, embryo implantation and spermatogenesis, and indirectly affects reproduction through influences on overall animal health. The scientific evidence so far obtained on mineral nutrition and its effects on reproductive traits in sheep and in goats can be controversial and inconclusive; however, attention should be focused on the presence of these elements on the diets since they are shown to be important for reproductive performance of these animals (Vázquez-Armijo et al. 2001).

Table 5. Effect of different levels of se on reproductive indices of Raieni goats (10 goats per treatment).

Se (mg/kg)	0.0	0.3	0.5	SE	P-value
Reproductive indices
Male	3.3	5	5	1.217	0.567
Female	6.7	6.7	4	1.846	0.535
Single	2.7	3	1.3	0.64	0.228
Twin	9.3	10.7	10	2.07	0.903

The effect of dietary vit E treatments on reproductive indices is listed in Table 6. The effect of vit E supplementation on reproductive parameters of Raieni goats was not significant (P > 0.05).

Table 6. Effect of different levels of vit E on reproductive indices of Raieni goats (10 goats per treatment).

Vit E (mg/kg)	0.0	20	50	SE	P-value
Reproductive indices
Male	5.3	4.0	4.0	1.26	0.704
Female	4.7	6.0	6.7	1.96	0.773
Single	2.0	2.7	2.3	0.79	0.842
Twin	10.7	9.3	10.0	2.07	0.903

The results of the current experiment are consistent with those of Macpherson (1994) who found that supplementation of vit E had no significant effect on birth and third month weight of Baladi lambs.

The interactive effect of Se and vit E on the productive performance of the kids are presented in Table 7. As the table shows the interactive effect of different levels of Se and vit E on the productive performance of kids was positive (not significant; P > 0.05). Our findings do not concur with those of El-Shahat and Abdel Monem (2011) who found that supplementation of diet with Se and vit E had a significant effect on total number of lambs and the incidence of ewes bearing twin.

Table 7. Interactive effect of different levels of Se and vit E on the productive performance of Raieni kids.

						Single & Twin kidding (%)		Sex of the kids
Treatments	No. of kidding goats	Total kids born	Kids born dead/goat	No. kids born alive/goat	No. weaned kids/goat	Single	Twin	Male	Female	Kid sex ratio
1	3	5	0	5	5	1 (33)	2 (67)	4	1	4
2	6	9	0	9	8	2 (33)	4 (67)	7	2	3.5
3	5	9	0	9	8	1 (20)	4 (80)	6	3	2
4	5	8	0	8	5	2 (40)	3 (60)	5	3	1.66
5	5	8	0	8	8	2 (40)	3 (60)	5	3	1.66
6	4	5	0	5	5	3 (75)	1 (25)	2	3	0.66
7	5	7	0	7	7	2 (40)	3 (60)	2	5	0.40
8	6	8	0	8	7	4 (67)	2 (33)	3	5	0.6
9	4	7	0	7	7	1 (25)	3 (75)	7	0	–

4. Conclusion

In conclusion, evidence from this study suggests that dietary supplementation with Se or vit E did not significantly affect biochemical metabolites. However, the interactive effect of Se and vit E was significant for birth weight, with a more positive effect observed when 0.5 mg/kg Se and 20 mg/kg vit E were added to the goats’ diet which could improve their reproductive performance and growth of their kids and also addition of more than on antioxidant could a positive effect on blood metabolites-related protein metabolism and T4 concentration.

Acknowledgements

The authors are grateful to Mr Mohammad Ali Mohammadi Nejad and staff of the Raieni goat breeding station for their useful and kindly help. The authors would also like to express special thanks to the director of the Raieni goat-breeding station for providing the research facilities. We have also a special thanks for Prof. Sandra Edwards at Newcastle University in the UK for the English revision of this manuscript.

Funding

This research project has been financially supported by the office of education and research from the University of Jiroft, Iran.

Additional information

Funding

Funding: This research project has been financially supported by the office of education and research from the University of Jiroft, Iran.