With dairy payouts almost as good as they have ever been, and demand for stock inflated by a current burst of conversion activity, stock prices are similarly near all-time highs. Calves are, of course, no exception, so it makes sense to do what you can to ensure the calves born on your farm get off to a good start. A 2015 study into prevalence of organisms causing calf scours found rotavirus on New Zealand dairy farms, and, of those farms studied, it found that 46% had rotavirus detectable in calves between 1 and 5 days old, rising to 57% in calves between 9 and 21 days old. Coronavirus was found in 14% and 31% of farms in the same respective age groups. Including Salmonella and Cryptosporidium, 97% of farms had one of these four organisms present.
Diarrhoea itself is costly, due to the risk of calves simply dying. Even in mild outbreaks with no deaths, the time and emotional cost on calf rearers dealing with sick scouring calves can be significant, and calves who do survive may have lifelong consequences. Studies have shown that calves affected by diarrhoea tend to be weaned later. The cause of this effect is obvious. A calf with diarrhoea undergoes a period of reduced growth whilst nutrients pass straight through its system in the diarrhoea. However, what is less apparent is microscopic damage incurred to the gut lining during the infection, and this can affect the digestive and absorptive capacity of the gut lining for the rest of the animal’s life. This can cause lifelong reduced growth rate, and reduced milk production. Essentially, a calf born with a great production potential can have that potential compromised forever simply through a bout of diarrhoea.
Calf scour vaccines are well established products in New Zealand, and they have a proven history of both reducing the presence and reducing the disease caused by the organisms against which they are designed. Rotavirus, Coronavirus and E. Coli antigens are contained in the common vaccines, and a new vaccine has recently been released which provides protection against Cryptosporidium as well. Vaccinating cows three weeks prior to calving induces antibodies against these causes of calf diarrhoea to be passed in colostrum for around nine weeks after calving. These antibodies serve two purposes. With well-managed colostrum feeding, these antibodies can pass directly from the colostrum into the newborn calf’s bloodstream, providing instant and lasting protection whilst the calf works on developing an immune system. Continued feeding of colostrum rich in these antibodies also acts to bind and attack these viruses and bacteria in the gut system of the calf, preventing them from ever attacking the calf in the first instance.
By using these vaccines, you can greatly reduce the risk of high-value replacement calves falling victim to diarrhoea early in life, and thus increase the chance that they can realise their genetic potential. As we are increasingly moving towards a focus on improved production efficiency to help meet emissions targets, (set by dairy consumers around the world), ensuring that potential is met becomes increasingly important, and hence the use of calf-scour vaccines makes increasingly good sense.
Salmonella is a calf diarrhoea pathogen not covered in any of the current calf scour vaccines, however herd vaccination against Salmonella will reduce shedding and transmission within a herd and consequently reduce the risk presented to calves.
