Don't buy calf scours!
South Dakota State University researchers examined the cause of a scours epidemic in one spring calving herd back in 2000. Results of the retrospective, record-based investigation suggested that introduction of foster calves was associated with the calf scours outbreak.
Prior to April 5, no scours cases had been observed, despite 39 calves being born. The calf scours epidemic was clearly in swing by the 45th day of the spring 2000 calving season and first cases of the epidemic were observed between the 31st and 40th days (April 5, 2000 through April 14, 2000). Following April 5, records indicated there was the introduction of at least 2 foster calves.
The outbreak commenced shortly after the introduction of foster calves.
Foster calves can introduce pathogens to a herd, and can shed calf scours pathogens in their feces even when feces appear normal. Because of this risk, the introduction of foster calves is not usually recommended. If introduced into a herd, foster calves (with their foster dam) should be isolated from the remainder of the herd until all calves are at least four weeks old. At that time, it is generally regarded as safe to commingle foster calf pairs with the remainder of the herd. — Glenn Selk, Oklahoma State University Emeritus Extension Animal Scientist