As winter begins to set in across the United States, many farmers will need to start thinking about their animals’ nutritional requirements. Plummeting winter temperatures may send many dairy operations reconsidering their winter survival tactics and preparing for disease challenges that can come with the change of the seasons.
One challenge that can often show up in dairy herds during this time is winter dysentery. Occurring from early fall through late spring, winter dysentery is characterized by the sudden onset of diarrhea and can affect 15 percent or more of the herd. Fresh blood in the feces may be present, as well as, dehydration, loss in body condition, respiratory issues like coughing and nasal discharge, and a varying decline in milk production of 10 percent or greater, are also noted. Winter dysentery has a high rate of morbidity, but a low rate of mortality. Twenty to 50 percent of animals in the herd will exhibit clinical symptoms within the first few days and the rest of the herd within a week to 10 days.
The causative agent in winter dysentery is still unclear. However, Bovine coronavirus (BCV) has been cultured from the feces of affected animals, which is also a culprit in bouts of diarrhea and respiratory disease in young calves. Additionally, elevated BCV titers have been measured in afflicted herds. Ingestion of contaminated feed or water is the most common route of infection. Viral particles in the respiratory secretions of affected animals can also exacerbate transmission.
Clinical symptoms of winter dysentery typically subside within two weeks of onset. However, the time to recover the loss in body condition and milk production can take months. Thus, financial ramifications of an outbreak of winter dysentery can be severe. Recovered animals appear to be immune from the disease from one to five years, but carrier animals can be a source of repeated outbreaks.
The first step in managing the disease is to stop the cycle. It is also recommended to caution access to outside visitors during an outbreak of winter dysentery. Controlling the movement patterns of cattle and people on the farm can be beneficial, as well as having farm employees working with cattle change out of soiled clothes and sanitize boots as often as necessary for their particular job. Eliminating manure contamination in water, feed, feed bunks, and feeding equipment is also critical in avoiding transmission of this virus.
Besides management practices, producers may also want to consider their nutritional programs in assisting the herd to get through an outbreak with less stress. Alternative non-antimicrobial products such as direct-fed microbials and/or mannan oligosaccharides (Bio-Mos®) have shown some benefits in improving the animal’s balance of intestinal bacteria (International Dairy Topics Vol. 4 No. 3, 2005).Direct-fed microbials and mannan oligosaccharides can help to maintain healthy immune systems in dairy and efficient nutrient transfer from cow to calf. Palatable feed and fresh water should be available at all times, and in severely affected cattle, fluid therapy should be administered. Currently, there are no vaccines for BCV.
In most cases, affected cattle recover spontaneously. However, measures such as proper hygiene, constant awareness, quarantining of new animals, and certified testing remain important and should continue to be used on the farm to help in preventing and treating potential outbreaks.