Comparison of selenium bioavailability in milk and serum in dairy cows fed different sources of organic selenium

Abstract

Context Selenium (Se) bioavailability is an important parameter to consider when supplementing trace minerals to optimise animal health and performance. Aims To assess the biological transfer of Se in milk and serum of three sources of organic Se in dairy cattle: two different pure selenomethionines (SM1, SM2) and Se-yeast (SY) containing selenomethionine, selenocysteine and other forms of organic Se. Methods Forty-five lactating Holstein dairy cows were randomly distributed in nine groups (three sources of organic Se supplemented at three doses: 0.1, 0.2 and 0.3 ppm organic Se in addition to 0.3 ppm of inorganic Se) and the Se concentrations in milk and serum were analysed at different times over 34 days of supplementation. Dry matter intake, milk yield, as well as milk fat and protein contents were recorded daily for each cow. Selenium bioavailability in milk was assessed as the ratio between amount of Se secreted in milk and amount of Se consumed. Key results The lowest Se dose (0.1 ppm), independent of source, did not allow detection a different pattern of transfer into milk and serum, suggesting that at this level, the Se supplied was mainly used to cover the animal needs. Supplementing SY at 0.2 and 0.3 ppm resulted in the most consistent secretion of Se into milk, whereas SM2 was most effective at increasing serum Se concentrations. Conclusions At the supplementing doses of 0.2 and 0.3 ppm, SY elicits an increased transfer of Se into milk concentrations compared with SM1 and SM2, whereas SM2 induces the greatest increase in Se serum concentrations. Implications SY is more effective than SM1 and SM2 at increasing Se transfer into milk. Supplementation of SM2 induces a pattern of Se transfer into milk and serum that differs from the other Se sources suggesting a different metabolism of this particular Se source.

The Efficacy of a Long-Acting Injectable Selenium Preparation Administered to Pregnant Ewes and Lambs

“…These observations were confirmed by other researchers who found that Se supplementation during pregnancy prevents Se deficiency in the offspring [ 25 ]. However, Barbé et al [ 26 ] observed that the Se content of milk is determined mainly by the availability of Se in cow diets. Selenium was not detected in milk or the serum of cows administered a low dose of the Se supplement (0.1 µg/g), which suggests that a low Se dose is utilized mainly to meet the animals’ physiological needs.…”

Combined Supplementation of Two Selenium Forms (Organic and Inorganic) and Iodine in Dairy Cows’ Diet to Obtain Enriched Milk, Cheese, and Yogurt

“…Furthermore, the slight increase observed in the Zn level is in accordance with the result obtained by Bagnicka et al [47], who observed higher levels of Zn after 90 days of supplementation with Se yeast. Some studies have shown that Se and I supplementation in feed affects the concentration of these trace elements in milk [4,12,22,47,68,80]. In a similar manner, Mehdi and Dufrasne [72] perceived that analyzing the Se content in cows' milk is a simple way to assess the Se status of a herd, and Berg et al [88] believed that the amount of I in cows' milk reflected the dietary I content and was also an indicator of the I status of the animals.…”

“…On the other hand, the level of Se in blood depends mainly on recent dietary intake and the bioavailability of the form of supplemented Se [52] since transformation pathways that take place in the rumen are highly dependent on the type of Se chemical compounds [53]. Inorganic salts, such as sodium selenite, are highly susceptible to dissolution and form elemental Se in the rumen environment [54], are poorly absorbed with a short half-life in the body, and are mostly excreted in feces [12,55] while organic sources such as Se yeast improve the bioavailability of Se, increasing its incorporation into the microbial protein as seleno-aminoacids in rumen metabolism [54,56]. Several studies observed a higher Se content in the blood samples tested when Se yeast, instead of sodium selenite, was added to the cows' diets [47,54,57,58] since organic Se forms more efficiently accumulate in tissues, being more bioavailable and less toxic than inorganic forms [12].…”

“…Inorganic salts, such as sodium selenite, are highly susceptible to dissolution and form elemental Se in the rumen environment [54], are poorly absorbed with a short half-life in the body, and are mostly excreted in feces [12,55] while organic sources such as Se yeast improve the bioavailability of Se, increasing its incorporation into the microbial protein as seleno-aminoacids in rumen metabolism [54,56]. Several studies observed a higher Se content in the blood samples tested when Se yeast, instead of sodium selenite, was added to the cows' diets [47,54,57,58] since organic Se forms more efficiently accumulate in tissues, being more bioavailable and less toxic than inorganic forms [12]. However, we observed that, although one of the diets was supplemented with an organic source of Se, we did not view significant differences in the blood Se levels.…”

“…Micronutrient deficiencies have a considerable negative impact on society, and the enrichment of food has become one of the most important and well-studied strategies to overcome this problem, which can also considerably affect farm animals, leading to significant economic losses [8,9]. In this context, Se and I are commonly supplemented in livestock feed to meet the dietary requirements of animals [5,10]; however, Se is regularly supplied in the form of inorganic salts, mainly sodium selenite, which is less bioavailable than organic sources, such as Se-enriched yeast [9,11,12]. However, excessive Se supplementation in the diet can cause toxicity, thus the signs of toxicity of Se generally begin to appear at Se levels of 5 to 8 mg/kg DM [1].…”