Here is Selena 20 selenium Vietnamese powder sold by the kilogram

HAN-SELENA 20 PREMIX 1 KG dietary supplement premix contains vitamin E and sodium selenite to meet the daily needs of animals. Pharmaceutical form powder for addition to drinking water. Composition each 1 kg contains: Vitamin E: 20000 mg Sodium Selenite: 800 mg. Indications to meet the daily needs of animals for vitamin E and selenium for animals exposed to stress. Target animals camels, cattle, horses, sheep, goats, poultry. Usage and dosages add to drinking water. A measuring scoop = 10 grams comes with the product. Camels, cattle, horses: 10 grams (1 scoop) for every 5 heads mixed with 60 liters of drinking water. Sheep and goats: 10 grams (1 scoop) for every 20 heads mixed with 50 liters of drinking water. Poultry: 100 grams for every 400 liters. Storage keep below 30 degrees Celsius. Packaging size 1 kg. Country of manufacture Vietnam.