The potential of silage lactic acid bacteria derived Nano-selenium as a dietary supplement in sheep

Context: Selenium (Se) is a trace element essential for cellular function in animals as a component of the enzymes glutathione peroxidase and iodothyronine-5-deiodinase. In many parts of Europe, Se is often deficient in livestock diets due to the low Se status of soil. Supplementation of diets with selenised-yeast (predominately as seleno-methionine) or inorganic sodium selenite is common practice in most livestock systems, including ruminants. Lactic acid bacteria have been shown to convert inorganic Se into predominantly elemental Nano-Se, which have been used recently in human pro-biotics as a less toxic form of Se. Therefore, silage lactic acid bacteria may provide a supplementation route of bioavailable Nano-Se for ruminants. Aim: Here we report the effect of feeding inoculated silage enriched with supra-nutritional Nano-Se (Selage) versus control inoculated silage (Silage) on the Se status of finishing lambs and their products, followed by a second study where blood parameters were investigated in ewes. Methods: In the first study 40 Charollais × Suffolk lambs (42 ± 1.7 kg) were paired according to weight and sex then allocated to the two treatments for 8 or 10 weeks. Uptake of Se into wool was temporally assessed as well as excretion into faeces. Se concentrations in blood and muscle, carcass characteristics and meat quality were reported post mortem. In the second study, individually penned Suffolk × Mule ewes (n = 12; 76 ± 4.5 kg) were offered the same diets as in the first study. Blood parameters were assessed at the start and after 6-weeks, with intake and excretion into faeces and urine assessed temporally through the study. Key Results: In the first study, DM intake was comparable 0.8 ± 0.03 kg/d, with Se concentrations of the diets significantly different resulting in intakes of approximately 0.14 vs. 1.60 mg/d on the Silage and Selage diets, respectively. This was reflected in higher Se concentrations in faeces (0.4 vs. 2.0 mg/kg DM; P<0.001); wool (0.11 vs. 0.25 mg/kg DM; P<0.001); blood (0.19 vs. 0.46 mg/L; P<0.001) and muscle (0.31 vs. 0.41 mg/kg: P<0.01). Colour (chroma) shelf life of the meat was significantly higher on the Selage treatment (8.05 vs 9.2 days; P<0.05). In the second trial, for ewes fed Selage blood seleno-methionine increased from 0.21 to 0.25 and seleno-cysteine from 0.25 to 0.35 mg/L after 6 weeks on treatment, whereas there was no change for ewes fed Silage. Glutathione peroxidase increased whilst haematocrit, haemoglobin and platelet count were shown to decrease during the study but with no difference between treatments. Conclusions: Nano-Se provided from the Selage treatment was shown to be available to sheep and improve shelf life with no adverse haematological effects. Implications: There is potential to use silage inoculants to provide bioavailable Se to ruminants. Further research is required to determine the most appropriate dose rate for animal performance and product quality.