摘要：Shortage of K-casein in milk was the cause of heat-labile milk. In the case of heated labile milk, the health condition of dairy cow was investigated which was involved nutritional deficiency of dairy cow. In the series of vitamin content measurements of blood of dairy cow, it was found that dairy cow of heated labile milk was lower in vitamin B12 content in their blood. There was about 2.89×10-4 mg/ml of vitamin B12 in the blood of normal dairy cow but just about 2.07×10-4 mg/ml in heated labile milk cow. Injection of Vitamin B12 to heat labile milk cow made the milk become heated stable normal milk. After treatment of mineral supplement at herd of dairy cow, the frequency of heated labile milk decreased from 18％ to 2％ and milk production increased from 14.5 kg to 18.5 kg per cow per day. Investigatio of several dairy farms, dairy cow had feeding mineral supplement, the quality of milk product was better than without supply one. And milk product was about 20％ higher than other one. Therefore feeding dairy cow the mineral supplement containing cobalt was important to dairy cow in Taiwwan and should not be neglected. We conclude that some heat labile caused by the shortage of cobalt in dairy cow and just enrich the mineral supplement during feeding, and the quality of milk will recover normally and increase the quantity of milk production.