Evaluation of selenium source on nursery pig growth performance, serum and tissue selenium concentrations, and serum antioxidant status

Lay Summary Selenium (Se) is an essential trace mineral for selenoproteins that are crucial for antioxidant status and all stages of animal growth, and Se deficiency may result in health issues in pigs. To meet the Se requirement, several inorganic or organic Se sources can be added to animal feed. Different Se sources have shown bioavailability differences that affect absorption and storage of Se and may improve animal performance. In this 35-d experiment, a total of 3,888 nursery pigs (initially 6.0 kg) were used to test three different Se sources added at 0.3 mg/kg concentration. One inorganic Se source (sodium selenite) and two organic Se sources (Se yeast and hydroxy-selenomethionine [OH-SeMet]) were used to formulate three experimental diets. Overall, pigs fed OH-SeMet had decreased gain and increased serum and tissue Se concentration compared with other treatments. There were similar results in measures of antioxidant status tested between treatments. In summary, compared to sodium selenite and Se yeast, OH-SeMet may have greater bioavailability as indicated by increased serum and tissue Se concentration; however, antioxidant status was similar between treatments and OH-SeMet tended to reduce growth performance compared with pigs fed sodium selenite. Organic selenium (Se) source (hydroxy-selenomethionine) increased serum and tissue Se status of blood and tissues in nursery pigs compared to an inorganic Se source (sodium selenite) with similar results in most antioxidant status tested. A total of 3,888 pigs (337 x 1050, PIC, Hendersonville, TN; initially 6.0 +/- 0.23 kg) were used in a 35-d study. At the time of placement, pens of pigs were weighed and allotted to one of three dietary treatments in a randomized complete block design with a blocking structure including sow farm origin, date of entry into the facility, and average pen body weight. A total of 144 pens were used with 72 double-sided 5-hole stainless steel fence line feeders, with one feeder serving as the experimental unit. For each feeder, 1 pen contained 27 gilts, and 1 pen contained 27 barrows. There were 24 replicates per dietary treatment. Diets were fed in three phases, and all contained 0.3 mg/kg added Se. A common phase 1 diet contained added Se from sodium selenite and was fed in pelleted form to all pigs from day 7 to approximately day 0. Three Se sources sodium selenite, Se yeast, and hydroxy-selenomethionine (OH-SeMet) were used to formulate three experimental diets in meal form for phase 2 (days 0 to 14) and phase 3 (days 14 to 35). During the pre-treatment period (days 7 to 0), there was a tendency (P = 0.097) of a difference in average daily feed intake between treatments, although no significant pairwise differences were observed (P > 0.05). There were no other differences in growth performance between treatments from days 7 to 0. Clinical disease attributed to Streptococcus suis was observed within the trial between days 0 and 14, and water-soluble antimicrobial therapy was administered to all treatment groups for 7 d. From days 0 to 35, pigs fed OH-SeMet tended to have decreased average daily gain (P < 0.10) and increased (P < 0.05) serum and tissue selenium concentration compared to other treatments. There was marginally significant evidence of a source x day interaction (P = 0.027) for total antioxidant capacity where the numerical increase over time was less for the OH-SeMet than sodium selenite or selenium yeast treatments. There was no difference (P > 0.05) in antioxidant status as measured by serum glutathione peroxidase or thiobarbituric acid reactive substances assay between treatments. In summary, compared to sodium selenite and selenium yeast, OH-SeMet may have a greater bioavailability as indicated by increased serum and tissue selenium concentration; however, antioxidant status was similar between treatments and OH-SeMet tended to reduce growth performance compared with pigs fed sodium selenite.