Some research suggests that organic forms of Zn may affect mammary gland health status. Supplementation of dairy diets with Zn methionine has reduced somatic cell counts in some studies but not in others reported that lactating cows supplemented with Zn proteinate had a lower rate of new intramammary infections than those supplemented with inorganic Zn oxide. He suggested that Zn proteinate may enhance resis- tance to mammary infections by increasing keratin synthe- sis in the teat canal.