Does Selenium Source Affect Nursery Pig Performance and Livability?

Abstract One of the key roles of selenium (Se) as an essential trace mineral is forming selenoproteins, which serve as antioxidant enzymes protecting cells from oxidative damage and are involved in immune cell functions throughout all stages of animal production. Sodium selenite has been widely used in growing pigs’ diets due to its low cost, even though it does not naturally occur, is carcinogenic, and has lower bioavailability compared to organic sources. Organic selenium sources, such as selenomethionine-based products like Se yeast or hydroxy-selenomethionine (OH-SeMet), have greater absorption and can enhance animal performance. Given the widespread inclusion of organic Se in sow diets and its growing application in nursery diets, it is essential to contrast the outcomes associated with each Se source. To this end, a total of 997 pigs (initially 5.9 kg of BW) were used in a 39-d trial. Pigs were placed in pens with 27 to 28 pigs each and allotted to 1 of 3 dietary treatments with 12 replicates per treatment. Treatments consisted of 1) sodium selenite, 2) Se yeast (Sel-Plex®; Alltech, Nicholasville, KY), and 3) OH-SeMet. Pigs were fed a two-phase commercial nursery program with 0.3 ppm added Se, comprised of corn and soybean meal-based diets formulated to meet or exceed the NRC (2012) nutrient requirements. From d 0 to 21, pigs fed Se yeast had greater (P = 0.050) ADG than sodium selenite, with OH-SeMet being intermediate. Also, Se yeast pigs tended to have better (P = 0.078) feed efficiency. In phase 2 (d 21 to 39) and overall (d 0 to 39), no differences were observed in any performance parameters (P 0.10), although Se yeast had numerically better ADG, ADFI, and feed efficiency in the overall period than the other Se sources. For health outcomes, Se yeast fed pigs had lower (P = 0.048) mortality and a greater (P = 0.031) percentage of full value pigs than selenite, with OH-SeMet being intermediate. In summary, the improvement in performance in early nursery, together with lower mortality, indicates the ability of Se-yeast to meet the goals of today’s swine industry.