Why farmers need to adding feed grade zinc sulfate monohydrate to raise livestock feed?

Feed grade zinc sulfate monohydrate produced by Rech Chemical Co. Ltd usually sells to feed industry customers. They add feed grade zinc sulfate monohydrate powder in feed additives to supply zinc of pig, poultry, cattle and sheep. Why farmers need to adding zinc to raise livestock feed?
 
Pig: If the content of zinc cannot reach the normal point in bags body, the piglets femoral become smaller, affect the development. It also affects the boar sperm production, for sows the entire reproductive cycle and zinc is inseparable. Such as sow zinc deficiency causes sow oestrus delay, prone to miscarriage, and so on and so forth.

Chickens, ducks, if there is a zinc deficiency in poultry, poultry feed intake, daily gain, laying rate, fertilization rate, and hatching rates fell.
Cattle and sheep: In the condition of severe zinc deficiency in body, cattle and sheep reproductive disorders would happen would make the bulls, and the lamb gonadal dysgenesis.

So pay attention to added zinc sulfate in the diet of livestock and poultry, can appear otherwise the above deficiencies, bring efficiency loss of production of farmers.