Open Veterinary Journal, (2023), Vol. 13(11): 1451–1457

Original Research

10.5455/OVJ.2023.v13.i11.8

Blood selenium and zinc concentration of female alpacas (Vicugna pacos) and their offspring during different physiological conditions

Sergio Antonio Vargas Mendivil*, Mariano Gonzalo Echevarria Rojas and Carlos Alfredo Gomez Bravo

Departamento de Nutrición, Facultad de Zootecnia, Universidad Nacional Agraria La Molina, Lima, Perú

*Corresponding Author: Sergio Antonio Vargas Mendivil. Departamento de Nutrición, Facultad de Zootecnia, Universidad Nacional Agraria La Molina, Lima, Perú. Email: s_vargas_mendivil [at] hotmail.com

Submitted: 05/08/2023 Accepted: 27/10/2023 Published: 30/11/2023

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Abstract

Background: Minerals are important for animals in many biological functions. There is scarce information, however, about micromineral content in the blood of South American camelids under their prevalent production system.

Aim: This study aims to determine whole blood selenium (Se) and serum zinc (Zn) concentrations of grazing alpacas at three different physiological states in the Peruvian Andean Highland.

Methods: Blood samples were collected for measurement of whole blood Se and serum Zn concentrations from 15 female alpacas at late gestation, peripartum, and late lactation, as well as their respective offspring, for them only two times were taken it account (10 days after birth and late lactation). The female alpacas at the beginning had a body weight of 47.5 ± 8 kg and an estimated age of 4.03 ± 0.93 years. Se and Zn content of pastures consumed by alpacas also were determined. The samples were taken during three different months according to the productive calendar of the alpacas.

Results: The content of Se and Zn of the diet selected by alpacas met the requirements for the physiological states they go through in comparison with literature references. Serum Zn concentration of female alpacas was higher in peripartum (0.26 µg/ml), compared to late gestation and late lactation (p < 0.05). A similar result was found in the case of their offspring at 10 days after birth (0.23 µg/ml) Zn concentration was higher than for late lactation (p < 0.05). Unlike Zn, in the case of Se, no differences were found between the physiological states studied for alpacas or their offspring.

Conclusion: Serum Zn concentration changes through late gestation, peripartum, and late lactation in the female alpacas and their offspring 10 days after birth and late lactation. Further investigation is needed to define the alpaca adequacy of Zn and Se in relation to the blood content of both minerals.

Keywords: Alpaca, Selenium, Zinc, Blood, Andean Highland.

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Introduction

Minerals are essential to perform basic biological functions for life; being fundamental in the productive, reproductive, and immunological performance of livestock animals. Selenium (Se) is related to antioxidant activity and animal growth, being part of the enzyme glutathione peroxidase and the enzyme 5-monodeiodinase (McDowell, 2003a). Zinc (Zn) participates among other functions as a cofactor and integral component of molecules (structural or functional), having immunological, metabolic, and performance repercussions (McDowell, 2003b). The status of a mineral is defined as the determination of the concentration of mineral in the soil, diet, and blood level, and the interpretation of the results to obtain a panoramic view of the impact of the mineral on the productive performance of the animal. However, in some cases, the analysis of minerals is only carried out in blood samples, since the samples of the diets that the animals consume are difficult to determine due to the amount ingested and their composition, as well as the different factors that could alter the concentration of a certain mineral: source, composition, and interaction. For example, in the case of selenium, inorganic forms (sodium selenite) have less absorption and retention than organic forms (selenomethionine) in the body. The concentration of selenium may be different if the pasture grows on alkaline (increased) or acidic (decreased) soils, or like the astragalus species where selenium is found in high concentrations, interactions with high concentrations of sulfur or iron can decrease its absorption in the organism (National Research Council, 2007; Herdt and Hoff, 2011).

There is scarce information regarding the mineral content of blood and the effects of physiological states on it, in the alpacas reared in the Andean Highland, with almost the majority of information coming from Europe (Husakova et al., 2014; Pechová et al., 2018), North America (Van Saun and Herdt 2014), and Oceania (Judson, 1999; Judson et al., 2011) all with important differences in the environment and diet to the prevalent situation in the Andean Highland. Specifically, Se and Zn concentrations in the pastures consumed by grazing alpacas in the Andean Highland are unknown, as are their concentration in the blood; not knowing whether both microminerals are at adequate or deficient levels and the impact of the different physiological states on them. Therefore, the objective of our work was to determine whole blood Se and serum Zn concentrations in grazing alpacas (mother and offspring) in the Peruvian Andean Highland at critical physiological states (gestation and lactation).

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Material and Methods

Location

This study was conducted in the district of Ocuviri, department of Puno, at an elevation of 4,397 m above sea level. The temperature during the year had a minimum of −11.2ºC and a maximum of 21.8ºC, with annual precipitation of 843 mm (SENAMHI, 2020). Alpacas were in extensive production systems, being fed based on the native pastures from the area without any kind of supplementation.

Animals

The present experiment included three physiological states for female alpacas (late gestation, peripartum, and late lactation) and two physiological states for their offspring (10 days after birth and late lactation). It was projected to work with 30 Suri female alpacas, which completed the three physiological states; however, due to the deaths of the offspring and abortions of the female alpacas, only 15 alpacas were counted at the end of the study, which went through the three physiological states. These female alpacas at the beginning of the evaluation were at 3 months before calving with a body condition score of 2.86 ± 0.41 and an estimated age of 4.03 ± 0.93 years. Body condition was evaluated as suggested by Van Saun (2009), and the estimated age through dental identification as suggested by Aragon (2005).

Sampling and analytical procedure

Blood samples were taken at three different moments: at the beginning of the rainy season (November 2018), alpacas in prepartum, with 37 ± 29.9 days before calving; in the middle of the rainy season (February 2019), female alpacas and their offspring, after 10 days of calving and being born, respectively (postpartum); and in the dry season (July 2019), female alpacas and their offspring, both in late lactation, with 162 ± 7.7 days after calving.

The technique used for blood sampling was external jugular vein puncture, extracting 5 ml of blood from both mothers and offspring using hypodermic needles 18G in mothers and 21G in offspring. Blood samples were collected in tubes with anticoagulant (EDTA) and without anticoagulant, for Se and Zn, respectively, it is worth mentioning the collected tubes for Zn did not have a rubber stopper. For the analysis of Zn, the formation of the clot was expected in the collected tubes. To separate the serum from the clot formed, the samples were centrifuged for 10 minutes at 2,500 rpm, and the collected tubes were sealed with parafilm, extracting the supernatant (serum) and placing it in Eppendorf tubes (2 ml), keeping them at −20ºC. A similar activity was carried out with the tubes that had the blood with anticoagulant, omitting the previous centrifugation step. 15 samples were collected for each physiological state, where the female alpacas had three physiological states and the offspring had two physiological states.

Pasture samples from diets that consumed female alpacas were collected at the same time (month and year) as described above for the blood samples. A manual simulation technique was used, which consists of observations of the individual grazing of the animals for 2–3 hours, near the grazing area, to later take representative manual samples of the natural grass consumed by the animal (Austin et al., 1983). These samples were collected from the observation of two alpacas from the herd, each with 30 feeding stations, cutting the forage at an approximate height of 5 cm above the ground (Burton et al., 2003). It is worth mentioning that for alpacas in particular, the consumption of natural pasture is variable, depending on the season, they can consume tall and low pasture, which are found at the root of the ground or at least 2 cm above the ground, being animals of selective consumption depending on their availability. To avoid contamination of the samples with soil minerals, it was decided to take samples in some cases above 5 cm. The 30 feed stations were averaging as a single sample, having at the end two samples from the two alpacas. In the case of zinc, the two samples obtained were analysed; however, in the case of selenium, a single sample from the mixture of the two samples taken was analyzed.

In the case of pasture, previously the samples were dried and ground, then subjected to acid digestion. First, the samples were mixed with a solution of nitric and perchloric acids (5:1) gradually raising the temperature to 175ºC, until the solution became clear. The samples were taken out and cooled then adding 15 ml of hydrochloric acid according to Bazán (2018). Finally, these solutions were used to determine Zn and Se. Zinc concentration was measured in the Laboratorio de Evaluación Nutricional para Animales, Facultad de Zootecnia (UNALM) using a flame atomic absorption spectrophotometry analysis (GBC model SavantAA ∑). Selenium concentration was measured by Unidad de Servicios de Análisis Químicos de la Facultad de Química e Ingeniería Química (UNMSM) using a graphite furnace atomic absorption spectrophotometry equipment (SHIMADZU, model AA6800). Both concentrations were determined in mg/kg of dry matter (DM).

Whole blood Se concentration was measured by Unidad de Servicios de Análisis Químicos de la Facultad de Química e Ingeniería Química (UNMSM) using a graphite furnace atomic absorption spectrophotometry equipment (SHIMADZU, model AA6800). The concentration of Se was determined in ng/ml of whole blood.

Serum Zn concentration was measured according to Soltero et al. (2007), briefly, the sample was mixed with 1 ml chlorhydric acid (1N) plus 1 ml trichloroacetic acid (20%), then rest for 10 minutes. After that, the solution was centrifuged, discard the precipitate, and save the supernatant. The supernatant was used to determine Zn concentration in the Laboratorio de Evaluación Nutricional para Animales, Facultad de Zootecnia (UNALM) using a flame atomic absorption spectrophotometry analysis (GBC model SavantAA ∑). The concentration of Zn was determined in µg/ml.

Statistical analysis

Means were calculated for pasture concentration data. In the cases of Se and Zn concentration in blood component means with SDs were calculated.

For analysis of data from whole blood Se and serum Zn concentrations, fixed block designs were carried out considering the alpacas as block and the physiological states as a factor (independent variable), two separate analyzes were made, one for female alpacas and the other for their offspring. For female alpacas, we considered three levels for physiological factor (late gestation, peripartum, and late lactation) and 15 fixed blocks (mother alpacas), and for their offspring two levels for physiological factor (10 days after birth and late lactation) and 15 fixed blocks (offspring alpacas). In the case of finding differences between the physiological states a least significant difference test was made. Statistical Analysis System (OnDemand for Academics) ran all the analysis designs.

Ethical approval

The animal care and experimental procedures used in this study conformed to the regulations and guidelines of the Animals Ethics Committee and the Ethical and Animal Welfare Committee of Universidad Nacional Agraria La Molina (TR. No 0.358-CU-UNALM) and the consent of the owner of alpacas.

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Results

Zinc and selenium content in pastures

The average concentration of Se in the pastures that consumed the female alpacas during three physiological states was 0.28 ± 0.04 mg/kg DM and for Zn concentration was 30.7 ± 9.1 mg/kg DM (Table 1).

Whole blood selenium concentration

Whole blood Se concentrations were 53.6 ± 13.9, 56.8 ± 14.4, and 48.2 ± 14.7 ng/ml for female alpacas at late gestation, peripartum, and late lactation respectively (Table 2). For their offspring, whole blood Se concentrations were 54 ± 14.1 and 53 ± 19.6 ng/ml 10 days after birth and late lactation, respectively. No significant differences were found between physiological states.

Serum zinc concentration

A higher serum Zn concentration of female alpacas was observed at peripartum (0.26 ± 0.2 µg/ml) (p < 0.05), than late gestation (0.15 ± 0.1 µg/ml) and late lactation (0.05 ± 0.04 µg/ml). On the other hand, the serum Zn concentration for their offspring was higher 10 days after birth (0.23 ± 0.2 µg/ml) (p < 0.05), than in late lactation (0.07 ± 0.04 µg/ml) (Table 2).

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Discussion

Serum Zn concentration was different between the physiological states of female alpacas: peripartum with a higher value than late gestation and late lactation. These differences can be explained because large amounts of Zn (blood serum) are used for the development of the fetus and the production of colostrum and milk, decreasing the reserves of this mineral in the mother (Pavlata et al., 2018). The colostrum can have a very high concentration of Zn compared to the mother's blood serum, indicating mobilization of Zn from the mother to the calf's first milk (Pavlata et al., 2004). Both processes coincide with what was determined by Badiei et al. (2011), who in addition to what has already been mentioned, add that 1 month after calving, serum Zn concentration tends to increase again, coinciding with what was determined by Meglia et al. (2004), Yokus and Cakir (2006), and Karatzia et al. (2016). Similar trends were determined by Akhtar et al. (2010), in buffaloes, showing that Zn concentration in the last third of pregnancy decreases compared to the initial stages of pregnancy and returns to rise during the lactation phase, as in sheep (Aliarabi et al., 2018). Serum Zn concentrations from the offspring were not the same between physiological states, lower values were in late lactation compared to peripartum. A similar trend was obtained in the study by Gallivan et al. (1995), impala lambs had high serum concentration compared to yearling impala. As the animal grows, Zn concentration decreases, and newborn animals have an elevated concentration, due to greater absorption in the small intestine and a difference in their growth rate (Miller and Cragle, 1995; Puschner et al., 2004). The time when taking the second sample (10 days after birth) when the main source of nutrition of the offspring was the milk (Pavlata et al., 2004) with a few pastures up to 2 months of age, compared when taking the last sample (late lactation), when the offspring it is near to be weaned, in October, having pastures with differences qualities, which explains the low concentration of zinc during late lactation.

Table 1. Selenium and zinc content of pastures consumed by alpacas during three physiological states.

Table 2. Whole blood selenium concentration and serum blood zinc concentration of female alpacas during three physiological states and their offspring.

The Zn concentration determined in the diets was like that found by Ojeda (2020). Likewise, as determined by Espinoza et al. (1982), and Zech and Feuerer (1984), in Bolivia, Burton et al. (2003) in Chile, Judson (1999), Judson et al. (2011), in Southern Australia. This concentration was adequate during late gestation, peripartum (≥30 mg/kg), and marginal during late lactation (20–29.9 mg/kg) (Van Saun and Herdt, 2014). According to the assessment of the Zn concentration in pastures, it would be expected that serum concentration during the first two physiological stages should be adequate and during late lactation be deficient, but not so low. Serum Zn concentration greater than 0.05 µg/ml was like that obtained by Rosadio et al. (2012), in vicuñas from Peru. However, Semevolos et al. (2013), found a higher concentration of this mineral in the United States, as did Dwyer et al. (2019), in New Zealand, and Van Saun and Herdt (2014), in North America. The low concentrations obtained can be attributed to factors such as management (stress, Zn sequestration), and the analysis protocol (elimination of the protein part). However, the evaluation criteria should not only be limited to the individual concentration of the mineral but also consider the concentrations of other minerals, to evaluate the interactions. In the case of Zn, this is less absorbed if there is a higher concentration of sulfur (S), copper (Cu), and iron (Fe) in the pastures. The S affects the availability of Zn in the rumen (Goff, 2018), and Cu if it is in a ratio of 50 to 1 with Zn, will affect the absorption at the level of the intestine (McDowell, 2003b; Goff, 2018), and Fe competes for the transport (DMT1) in the same area (intestine) and within the blood (plasma, transferrin) (Georgievski et al., 1982). Using data from a first experiment (carried out in some points that cover the highlands of Peru), that is not yet published, added to what was mentioned above. The S concentration was in the adequate range (0.15%–0.20 % DM), so its antagonistic role can be ruled out. On the other hand, the Fe concentration was excessive (>400 mg/kg), which could alter the absorption of Zn at the level of the apical membrane of enterocytes and in its transport at the blood plasma level. As for the Cu concentration, the average was 14.45 mg/kg, considered adequate, analyzing the Cu: Zn ratio, this was 0.47:1, so Cu could not intervene in the absorption of Zn at the gut level.

On the other hand, the non-variation of whole blood Se concentration of female alpacas during the three physiological states: late gestation, peripartum, and late lactation, was similar to that determined by Herdt (1995), in llamas, where they found no differences between serum Se concentration, during pregnancy, and after calving, furthermore to the determined by Kachuee et al. (2019), in goats, where they measured whole blood Se concentration weeks before calving and during calving. As in the female alpacas, in their offspring, no difference was found.

Regarding the relation between Se concentration in pastures and whole blood, the Se concentration in pastures was like that determined by Judson (1999), Judson et al. (2011), in Southern Australia. However, it was higher than that determined by Espinoza et al. (1982), in Bolivia. According to Van Saun and Herdt (2014), Se in pastures is adequate (>0.2 mg/kg), so it would be expected that whole blood Se concentration is adequate. Whole blood Se concentration in this study was higher than that found by Ellison (2006), in alpacas bred in New Zealand, and by Judson (1999), Judson et al. (2011) in alpacas raised in Southern Australia. However, our concentration of Se was lower compared to that determined by Husakova et al. (2014), in alpacas raised in Europe, agreeing with that found by Chicaiza et al. (2016), in Ecuador. Likewise, in other species, such as llamas raised in the United States (Smith et al., 1998), as well in camels (Faye and Seboussi, 2009). Considering what is mentioned by Van Saun and Herdt (2014), the whole blood Se concentration obtained in the present study is deficient, the sampled alpacas should show some clinical sign of deficiency (weakness, stiffness of the limbs, white muscle disease, susceptibility to bacterial diseases, metritis), however, none of these signs were observed.

Nonetheless, Judson et al. (2011) and Husakova et al. (2014), mentioned in both publications that although the values obtained were not that recommended by Van Saun and Herdt (2014), the alpacas did not show clinical signs of deficiency, considering the ranges found adequate for their countries. Perhaps, in our case to confirm this assessment, the interaction of Se with other minerals should be also considered, for example, Se may not be absorbed due to modifications at the rumen by S (Fowler, 2010; Herdt, 2011; Van Saun and Herdt, 2014) and in the small intestine by Fe (Semevolo et al., 2013; Mehdi and Dufrasne, 2016). As in the case of Zn, comparing Se concentrations with unpublished data obtained from a first experiment, the average S concentration is within the appropriate range (0.15%–0.20%), so it would not affect the Se availability. Regarding the Fe concentration, the values were excessive (>400 mg/kg), iron to be absorbed must be as ferrous (Fe⁺²), in the diet it is generally found as ferric (Fe⁺³). In ruminants, at the level of the abomasum, ferric can be reduced to ferrous by the action of acids and at the level of the duodenum by the action of enterocyte ferrireductase (Goff, 2018). If there was an excess of Fe, this trace mineral in the form of ferric could antagonize Se absorption by forming complexes in the duodenum, which would decrease its absorption.

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Conclusion

Serum Zn concentration of female alpacas varied among physiological states, being higher after peripartum (p < 0.05), compared to when they were in late gestation and late lactation. Whole blood Se concentration of female alpacas does not change among physiological states, having similar values in late gestation, peripartum, and late lactation. In the case of the offspring, serum Zn concentration was higher 10 days after birth than late lactation (p < 0.05). On the other hand, no difference was found between peripartum and late lactation in whole blood Se concentration.

For extending understanding of Se and Zn content in the blood of alpacas works should be conducted in pasturing areas with contrasting content of those minerals or simulated in experimental trials. In addition, it is advised to take samples from the liver and milk (colostrum and during lactation) to have greater detail and explain the mineral distribution phenomena.

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Acknowledgments

The authors are grateful to the Universidad Nacional Agraria La Molina.

Conflict of interest

There is no conflict of interest to public this article.

Funding

Funds for this research were provided by CONCYTEC through a support project (N° 178-2015-FONDECYT) to the Ph.D. program in Animal Science of Universidad Nacional Agraria La Molina.

Authors' contributions

All authors contributed to the study’s conception and design. The investigation, formal analysis, writing the original draft, resources, software, validation, formal analysis, review, and editing were performed by Sergio Vargas, Carlos Gomez, and Mariano Echevarria. The first draft of the manuscript was written by Sergio Vargas and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Data availability

The data that support the findings of this study are not openly available due to reasons of sensitivity and are available from the corresponding author upon reasonable request.

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