Diarrhea or scours is the first leading cause of death in un-weaned heifer calves. It occurs most frequently between days 3 and 30 after birth, depending on the susceptibility of the individual animal and the cause of this multifactorial problem. According to the 2011 National Animal Health Monitoring System survey, diarrhea and digestive problems affect 25.3% of pre-weaned heifers and of these, 18.2% are treated. In addition, death rate in pre-weaned heifers is 7.8% with diarrhea accounting for 56.5% of this mortality.
Diarrhea is affected by pathogen exposure, calf management, environmental conditions, nutritional and immune status. Adequate amount and timely intake of colostrum is critical for calves to survive it. Once the intestinal epithelium is “closed” (first 1-2 days) to the initial absorption of large molecules, it then acts as a barrier to pathogens. The intestinal integrity of this epithelium is then critical to protect the young calf from bacterial challenges. It has been suggested that Zn is essential for normal function of this intestinal barrier, and the regeneration of its damaged epithelium.