Department - Author 1

Dairy Science Department

Degree Name - Author 1

BS in Dairy Science



Primary Advisor

Leanne Berning


The objective of this study was to discover the cause of a major diarrhea outbreak and fifteen pound decrease in milk production that simultaneously took place in a dairy herd located in California’s central valley. Throughout the duration of the problem there were five primary areas considered to be potential causes. These potential causes included silage quality, disease, water quality, almond hulls containing high levels of mycotoxins, and feed ration issues. The study used data from four different silage piles, each having different issues. Among these were issues of poor fermentation, low moisture content, high ash levels, and poor ensiling. Fecal, blood, and water samples were collected to test for diarrhea causing diseases such as salmonella and Bovine Viral Diarrhea Virus (BVD). Further analyses were performed on the water to test for high salinity, nitrate, and heavy metals. Along with these two tests, a necropsy was performed on an infected cow to locate any indication of disease or abnormality within the animal’s internal organs or blood. Following the necropsy, BCS and fecal scoring was administered to 400 and 420 animals respectively. These scorings were used to gauge the overall condition of the herd. Following the scorings a rumenocentisis was performed on nine animals to determine an average rumen pH level throughout the herd and whether or not there was a presence of sub-acute ruminal acidosis (SARA). The last potential cause analyzed was the feed. Feed issues included extreme mycotoxin levels in a portion of the almond hulls, sorting and particle size, as well as a possible poor balance of energy and protein in the ration. Unfortunately, none of these causes were singled out as the primary problem in the herd. Conducting these tests did however allow us to determine deficiencies within our ration and silage. The final conclusion after eleven weeks of searching was that the dairy encountered a perfect storm of several destructive events occurring at once. These events negatively impacted the rumen’s ability to digest feed properly, which resulted in the herd-wide diarrhea and reduced milk production. Further studies on this case may produce a single specific cause that may help prevent its reoccurrence in the future.