light, they must be seen as distinct selenium preparations. Given the highly regulated nature of the use of selenium and selenium products, one can easily find much informa- tion in relation to areas such as selenium source toxicity and stability. This type of information allows end-users to make informed decisions as to the suitability of individual prod- ucts for both their production systems and for end use.


Selenium source stability in premix and feed Taken from regulatory opinions on the materials, a differ- ential examination of the available stability data on organic selenium yeast and the synthetic selenium sources is high- lighted in Table 1, from which notable differences between them can be appreciated. Perhaps some of the most striking comparators are the notable differences between their stabilities in the premix. The instability of one of the synthetic selenium sources was quite noticeable, with recovery after three, six and nine months being reported as 55%, 54% and 37%, respectively. Examination of the other synthetic source did not show the measured stability of the actual compound and instead reported it for a non-selenised variant molecule. Addition- al questions remain about the stability of the synthetic sources in compound feed and after pelleting, with either insufficient data being generated or no direct measurement of stability being made. In contrast, the organic selenium yeast sources display high levels of verified stability in premix, compound feed and after pelleting, albeit with further source-dependent differences noted between them.


Table 1 – Selenium source stability


Selenium Yeast A


Shelf life


• Yeast A: 24 months (at least)


• In premixes: 12 months


• In feeds: 6 months • Pelleting: Stable to heat treatment


Selenium Yeast B


Shelf life


• Yeast B: 12 months (at least)


• In premixes: 4 months


• In feeds: 3 months • Pelleting: Stable to heat treatment


Sourced from EFSA regulatory opinions Chemically


synthesised Selenium 1


Shelf life


• 12 months • In premixes: Unstable • In feeds: Not determined (unsuitable study)


• Pelleting: Insufficient data


Chemically


synthesised Selenium 2


Shelf life


• 12 months • In premixes: Not directly determined


• In feeds: Not directly determined


• Pelleting: Not directly determined


Given the rising costs of raw materials and additives, premix and feed manufacturers are unsurprisingly placing increasing scrutiny on formulations and, in particular, on the stability of individual materials. Potential losses due to interactions in the premix or as a result of pelleting are of considerable concern.


Differences in toxicity between selenium sources Table 2 highlights the differential toxicities associated with inorganic, organic and chemically synthesised sources of se- lenium. The quite distinct and notable differences between selenium sources are of interest in this data. The organic selenium yeast product has relatively little, if any, negative connotations associated with its use. In contrast, the inorganic and synthetic selenium sources have clearly defined toxic attributes, which are notably quite similar with respect to their acute oral toxicities. The subtleties associated with the toxicities of liquid and solid


Table 2 – Selenium source toxicity and hazard labelling. Labelling


Test Substance Species/strain (mg/kg/bw) LD50


Selenium Yeast


Sodium Sele- nite


Rat


(CHS Sprague- Dawley)


Rat


(CHS Sprague- Dawley)


5-50 >2000 according to


Regulation (EC) No 127212008


None required None required Danger


Acute toxicity: Oral Category 2 Acute toxicity: Inhalation Category 3 Sensitization: Skin Category 1 Specifi c target organ toxicity, repeated exposure Category 2 Hazardous to the aquatic environment, acute hazard Category 1 Hazardous to the aquatic environment, long-term hazard Category 1


Synthetic Se 1 Rat 4 Danger


Acute Toxicity: Inhalation, Category 3 Acute Toxicity: Oral, Category 3 Specifi c Target Organ Toxicity (repeated exposure), Category 2 Aquatic Toxicity (Acute), Category 1 Aquatic Toxicity (Chronic), Category 1


Synthetic Se 2 (2% Se, liquid)


Synthetic Se 2 (2% Se, solid)


Rat Rat 10-25 10-25 Danger Danger


Acute oral toxicity, Category 3 Acute inhalation toxicity, Category 4 Serious eye damage, Category 1


Acute oral toxicity, Category 3 Acute inhalation toxicity, Category 4 Combustible Dust


H300+H330 Fatal if swallowed or if inhaled H315 Causes skin irritation H317 May cause an allergic skin reaction H319 Causes serious eye irritation H411 Toxic to aquatic life with long lasting eff ects.


H301: Toxic if swallowed. H331: Toxic if inhaled. H373: May cause damage to {organs} through prolonged or repeated exposure. H400: Very toxic to aquatic life. H410: Very toxic to aquatic life with long lasting eff ects.


H301 Toxic if swallowed. H318 Causes serious eye damage. H332 Harmful if inhaled.


H301 Toxic if swallowed. H332 Harmful if inhaled. May form combustible dust concentrations in air.


▶ ALL ABOUT FEED | Volume 30, No. 5, 2022 23 None required None required


Signal word


Classifi cation of the substance or mixture


GHS Hazard Phrases


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