Introduction

Selenium (Se) is a trace mineral element with antioxidant activity that together with vitamin E performs essential functions to prevent cellular damage (^{Mahmoud et al., 2013}). Therefore, both are part of the body's antioxidant system against oxidative stress, which is a condition that results from the imbalance between reactive oxygen species (free radicals and antioxidants in the body, which can lead to sperm damage). Therefore, both are part of the body's antioxidant system against oxidative stress, which is a condition due to imbalance between reactive oxygen species (free radicals and antioxidants in the body, which can lead to sperm damage, deformities and male infertility (^{Bansal and Bilaspuri, 2011}; ^{Agarwal et al., 2014}). The main function of Se in the organism is as a component of several selenoprotein enzymes (^{Silva et al., 2000}). The enzyme glutathione peroxidase (GSH-Px) contains Se in its chemical structure, and one of its functions is to prevent free radicals formation, thus preventing damage by tissue oxidation (^{Holben and Smith, 1999}). There is a selenoprotein with relevant protective functions in the mitochondrial capsule of the sperms (^{Ahsan et al., 2014}). In stallionsrams, Se and vitamin E improved semen quality, associated with a higher testosterone concentration and increased activity of the GSH-Px enzyme in blood serum (^{Mahmoud et al., 2013}). In male goats, organic Se improved the antioxidant status, testosterone and T₃ levels in seminal plasma and blood serum, which gives greater protection to sperms against oxidative damage, an important aspect for production of good quality semen ( ^{Kumar et al., 2013}). In buffaloes, organic and inorganic Se improved semen quality and increased testosterone and Se content in blood serum (^{El-Sharawy et al., 2017}). Boar spermatozoa with SE Se deficiency have a low fecundating capacity due to their limited mobility associated with abnormal development of their flagellum (^{Ahsan et al., 2014}). In dairy goats, the Se and vitamin E deficiency reduced the immune response and compromises the health and productive behavior of the female and her offspring (^{Ramírez-Bribiesca et al., 2005}).

The inclusion of Se in the diet, or by parenteral application, improved weight gain in lambs, the fertility of the sheep and the immune response in both (^{Vázquez-Armijo et al., 2011}); the above is conditioned to the achievement of the required Se concentrations in tissues and body fluids (^{Shamberger, 1983}). The intraruminal Se supply in boluses increased the Se concentration in blood, improved mobility and sperm viability, as well as the response to the integrity of the sperm's cell membrane (^{Kendall et al., 2000}). The Se and Zn supply in humans has shown intrinsic functions in spermatogenesis and in the general oxidative state, which suggests that both microminerals have important functions in stallion ram reproduction (^{Irvine, 1996}; ^{Vézima et al. , 1996}; ^{Oguntibeju et al., 2009}; ^{Kumar et al., 2013}).

The Se deficiency affected the health and production in sheep, in lambs caused high mortality during lactation and growth, reduced the weight gain of developing sheep and caused reproductive problems such as retained placenta in sheep and a lower quality of the ejaculate in stallions rams (^{Andrews et al., 1975}; ^{Allen et al., 1986}; ^{Kendall et al., 2000}). At the center most areas in Mexico sheep showed microminerals imbalances, with severe deficiencies of I, Se, Zn and Cu. Still, there are no mineral supply programs established to correct these deficiencies, and evaluate sheep response (^{Vázquez- Armijo et al., 2011}). ^{Ramírez et al. (2004)} diagnosed Se deficiencies in ovine flocks at Tlaxcala and Puebla, Mexico. The lack of Cu is associated to the low content of Se in the soil and therefore forages, the low pH in these soils, and to excess Fe in the forages and soils, which affects its absorption and serum content in sheep (^{Domínguez-Vara and Huerta-Bravo, 2008}). Goiter problems in sheep are related to a natural I deficiency, which probably involves the lack of Se and pollutants presentce in the environmental that cause endocrine disorders (^{Domínguez-Vara et al., 2017}). Therefore, these mineral imbalances are factors that affect the health, growth and reproduction in ruminants (^{Minson, 1990}). There is a close relationship between the testicles size and semen production; thus, stallions rams with small testicles may not produce enough sperm during the breeding period to achieve a good fertility rate (^{Mahmoud, 2013}). During the breeding season, increaserise of sexual activity in rams increased their nutritional requirements for semen production in a short period (breeding season), which can induce se Se deficiency and cause greater oxidative stress, with lower semen production and quality (^{Ahsan et al., 2014}; ^{Zubair et al., 2015}). In small ruminants, Se supply to supplement the contribution of the forages, includes adding premixes to their food, subcutaneous or buccal application in solutions and boluses or intraruminal Se tablets. The last method allows Se to be complemented in a practical, safe and effective way at a low cost (^{Langlands et al., 1994}, ^{Ramírez-Bribiesca et al., 2004}; ^{Revilla-Vázquez et al., 2008}).

This study aimede aim of this study was to evaluate the effects of the supplementing Se in intraruminal bolus on ovine stallions rams of the Hampshire and Suffolk breeds on their blood variables, glutathione peroxidase enzyme activity, serum Se concentration and characteristics of the ejaculate during the reproductive season. We hypothesizedOur hypothesis was that Se delivered in prolonged release intraruminal bolus increases the concentration of that mineral, the activity of the enzyme GSH-Px in the blood, and improves the quality of the semen during the breeding season of the rams.

Materials and Methods

Results and Discussion

There were no effects due to the interactions on the analyzed productive and blood variables (p > 0.05). At the end of the experiment Suffolk stallions rams that received the Se supplement had higher LW (p ≤ 0.05) and GSH-Px activity (p ≤ 0.05), compared to those whithout the Se bolus. The supplement with Se or the race breed did not change the scrotal circumference, body condition, hematocrit, hemoglobin or serum Se content (p > 0.05) (Table 1). ^{Mahmoud et al. (2013)} did not observed no effect of the Se combined with vitamin E in the LW, weight gain or scrotal circumference on stallionsrams. The hematocrit, hemoglobin and Se serum content were adequate as described by ^{Wheatley and Beck (1988)} and ^{Puls (1994)}. In contrast, GSH-Px activity was deficient in both breeds with and without the Se bolus supply, since the normal activity value for sheep is 130 U g^-1 Hb (^{Ceballos and Wittwer, 1996}). The Se bolus was increased, consistently and sustained, the activity of the GSH-Px enzyme in the rams treated during the study period; however, although the Se concentration in blood serum was adequate for both groups of stallions rams with and without Se, the GSH-Px enzyme activity was deficient. The significant increase of the Se level in blood serum of rams treated with the Se bolus is consistent with the results from ^{Kumar et al. (2013)} in goat stallions males treated with organic Se and Zn, as well as with the results from ^{El-Sharawy et al. (2017)} in buffaloes treated with organic Se (Se yeast) and inorganic Se (sodium selenite). However, in contrast to our results, sodium selenite combined with vitamin E produced adequate activity of the GSH-Px enzyme in Ossimi breed stallions rams of the Ossimi breed (^{Mahmoud et al., 2013}).

During the study, and between the months the LW mean values for PV, scrotal circumference and body condition from the stallions rams were similar (p > 0.05) (Table 2); In in contrast, the hematocrit mean values, hemoglobin, GSH-Px activity and Se content in blood serum were different (p ≤ 0.05) (Figure 1 and Table 2). The hematocrit value was lower in July and higher in October, but with adequate levels throughout the period (29 to 38 %). The hemoglobin content was adequate (8 to 16 mg dL^-1) (^{Puls, 1994}). The GSH-Px enzymatic activity was lower during July and higher in January; however, according to the optimum range indicated by ^{Ceballos and Wittwer (1996)}, the GSH-Px enzymatic activity was low, and only during January it had values higher than 130 U g^-1 Hb. The Se level in blood serum was adequate (0.08 to 0.5 μg mL^-1) for the Se supply, according to the range proposed by ^{Wheatley and Beck (1988}) and ^{Puls (1994)}. ^{Kendall et al. (2001a}, ^b) observed effects on the Se serum content and increased GSH-Px activity of the enzyme when giving Se in intraruminal boluses. However, the GSH-Px activity, of both stallions rams groups, was less than 60 U g^-1 Hb in the basal samplings from July ton September and October (Figure 1). Although the GSH-Px activity was higher in the sires rams treated with Se, only in January it was higher than 130 U g^-1 Hb. Kendall et al. (^1997a, ^b) found similar Se serum levels in Se treated lambs, with Co and Zn in a soluble crystal bolus, although serum Se was adequate in the control and treated group. Similar results were found with intraruminal boluses with Se, Co and Zn in sheep (^{Kendall et al., 1997a}, ^b, ; ^{Kendall et al., 1999}, ²⁰⁰⁰). Therefore, the intraruminal application of boluses with Se is an adequate, practical, safe and economical method to provide a sustained supplement with trace minerals, such as Se, to improve semen quality during the reproductive period

Figure 1 GSH-Px enzyme activity (U g^-1 Hb) in blood from Hampshire and Suffolk rams with or without selenium in an intra-ruminal bolus. Samples 1 to 3 correspond to weeks 1, 2 and 3 of July; samples 4 to 10 correspond to August 2005 to February 2006. 

There was no interaction effect for semen quality variables (Table 3). Greater motility of the sperm was induced (p≤0.05), also the number of live (p≤0.05) and normal (p ≤ 0.01) sperm in the semen increased. Suffolk stallions rams showed higher semen quality in terms of their volume (p ≤ 0.01), color (p ≤ 0.05), density (p≤0.01) and concentration (p≤0.05). The extracted ejaculates from January showed higher values in the mobility, density (p≤0.01) and concentration variables (p ≤ 0.05) from sperm cells.

The significant increase in the mobility variables, concentration, live and normal sperm in the ejaculated semen of the sires rams treated with Se is consistent with the results reported by (^{Mahmoud et al., (2013)} for Ossimi breed stallions rams of the Ossimi race treated with Se and Vitamin vitamin E and, besides, besides, with the results in buffaloes (El-Sharaw et al., 2017)treated with Se yeast and sodium selenite (^{El-Sharaw et al., 2017}). Similarly, ^{Kumar et al. (2013)} indicated that goat stallions males treated with organic Se and Zn significantly improved their antioxidant status, the sperm wasere better protected from oxidative damage and the sperm quality was a better.

The increase in the sperm cells mobility, as well as the percentage of live and normal sperm from sires rams supplemented with Se, is probably related to the increased activity of the GSH-Px enzyme promoted by the Intraintra-bolus ruminal bolus. This coincides with findings from ^{Kendall et al. (2000)} in sires rams treated with soluble crystal boluses containing Zn, Co and Se. The additional Se supplied with intra-ruminal bolus increased GSH-Px enzyme activity through its antioxidant function, providing greater protection against spontaneous lipid peroxidation of the plasma membrane in sperm cells, creating a barrier with selective permeability, supplying enzymes and cytoplasmic substrates that increase mobility and survival of the spermatozoid (^{Álvarez and Storey, 1984}; ^{Zubair et al., 2015}). Therefore, in sires rams that received the Se bolus, semen quality was probably improved by the formation of selenoproteins in the testicular tissue, with greater spermatogenesis stimulation (^{Ahsan et al., 2014}). It directly affects directly the interstitial cells of the testes, thus improving testicular function and semen quality (^{Underwood, 1977}), and indirectly, via the effect on hormones secretion from the anterior pituitary gland (^{Yousef et al., 1990}). The supply of Is Se combined with vitamin E increases the testosterone serum concentration, the activity of the GSH-Px enzyme, and altogether a greater manifestation of male secondary sex characteristics (^{Bearden and Fuquay, 1997}, ^{Mahmoud et al., 2013}). BesidesIn addition, Se is necessary for germ cells development in the testes during spermatozoa formation and has positive effects on the total germ cells in adults (^{Liu et al., 1982}). In the field, the improvement in variables indicated in our study, can favorably influence the quality of the ejaculate and, therefore, in the semen fertility of the stallionsrams; however, in sheep, these results should be confirmed with new studies.

Conclusions

Soluble crystal boluses with sodium selenite increase Se concentration in serum and GSH-Px enzyme activity in a sustained manner; in addition, they improve the mobility and viability of the ejaculate in Hampshire and Suffolk stallionsrams.