The following discussion comes from a recent query submitted by a dairy producer to the AgriLabs website. Dr. Travis Thayer of AgriLabs Technical Services responds:

 

Producer: We had our first known Salmonella cow in August 2004 and multiple cases thereafter for the next month. We worked with our veterinarian to figure out what it was and how to control new cases. Our veterinarian recommended vaccination with the Salmonella Newport Bacterial Extract Vaccine (We just call it SRP) as part of our control program. The cows are now under control, with our last probable case being about one year ago. Throughout this time, we have continued fighting Salmonella diarrhea in our calves at 7 to 10 days of age. Thetypical case is a one-week-old calf pulling off the nipple while suckling and having a pasty yellow/grayish diarrhea, often with bloody intestinal casts in it. These scours have beensampled multiple times since 2004 and it always comes back as Salmonella typhimurium or one time, dublin. I am sure it is still Salmonella we are fighting.   Luckily we are saving calves, but there is a huge investment of time and money that is wearing on us. What can we do to help combat this in our calves?

 

Dr. Thayer: The first thing I would ask is when did you last run diagnostics on the affected calves? What tests were runand what were the findings? Did you culture for only Salmonella? Did you also look for rota/corona/E.Coli/Crypto? Salmonella’s presence often is overlaid by other pathogens, meaning that you may find some Salmonella, but it may not be the primary problem. Often other diseases can have similar clinical symptoms, and repeat testing should be done on a regular basis to confirm that Salmonella is still the culprit. You may have diagnosed Salmonella a year ago, and this calf now looks just like that calf did a year ago, but it could be a different pathogen. Even if you still find Salmonella by running diagnostics, and you exclude all of the other pathogens as a cause, you gain some value by getting regular MIC profiles run on your isolates so that you can modify your antibiotic treatment regimen appropriately.

 

Producer: Should we make any changes in vaccinations? We follow a precise vaccination schedule. We dose heifers with SRP at six weeks prior and again at three weeks prior to calving. Cows are vaccinated at dry off (45 to 60-day dry period). All cows were vaccinated and boostered October 2004 and November 2004 and are getting yearly boosters. Our colostrum program involves feeding two bottles of the dam’s colostrum as soon as possible, and using frozen colostrum if the dam doesn’t provide sufficient quantities. Then we give calves pasteurized whole milk from hospital cows and, after two weeks, switch to bucket feeding.

 

Dr. Thayer: To protect young calves, I recommend dry cow vaccination and good colostrum management. From your description of your program, it sounds like you have a good system in place. One possible thing to discuss with your veterinarian would be to move the SRP vaccination to the end of the dry period, when the cow gets moved into the closeup/ prefresh group. While no controlled studies have been done on colostral transfer of anti SRP antibodies into the calf and the degree of protection provided, Epitopix, the manufacturer of the vaccine, has documented high levels of anti-SRP antibodies in calves fed colostrum from cows vaccinated with the SRP product. In general, higher antibody levels against a bacteria mean higher levels of protection against that bacteria.

Moving that shot closer to calving may result in higher antibody levels in the colostrum, which may provide more effective protection. Also, here are a couple of general suggestions-you likely are already using these practices on your dairy, but I think they are important enough to mention. First, use a colostrometer to evaluate colostrum quality in the dam. If it is particularly good quality, you can bank it for use with future calves. Second, throw out any colostrum with any visual evidence of blood. Bloody colostrum has a lot of iron   in it from the hemoglobin, making an excellent growth medium for bacteria.

Third, when harvesting colostrum, pour immediately into individual bottles, rather than pooling colostrum. This allows the colostrum to cool more quickly. Also, even if 1 cow’s colostrum is contaminated, it will only affect the individual calves fed that colostrum. Pooling colostrum from individual animals together means that one cow’s contaminated colostrum will contaminate all the

colostrum, potentially affecting all of the calves, rather than just a few.

 

Producer: We prepare the feeding equipment by soaking the bottles and nipples in a bleach-water bath at all times and thenrinsing with water prior to each feeding. Is this an adequate sanitation procedure, or should we be doing something else?

Dr. Thayer: Your intentions are good in your practice of soaking bottles and nipples in bleach water prior to feeding. However, this may not be as effective as one might think. Although sodium hyprochlorite (bleach water) is a very effective way of sanitizing things, it is rapidly deactivated by any kind of organic material and is relatively unstable. Thus, the initial concentration you put in the water might not hold for as long as you think. I would rinse the bottles and nipples well with hot water first, preferably as soon after use as possible. Then I would scrub the bottles and nipples with a brush and a good bactericidal soap/product. At this point, you could briefly place them briefly in a bleach solution. Then, remove from the bleach, invert, and allow to air dry before use.

 

Producer: At first sign of inappetance, we give 1.5 cc of Excenel per day for three days in a row, adding electrolyte therapy, as needed. Milk feedings continue throughout the diarrhea.

 

Dr. Thayer: Excenel and other ceftiofur antibiotics are often good antibiotic choices for Salmonella. However, an increasing number of strains of Salmonella and other pathogenic bacteria are resistant to multiple antibiotics. As previously mentioned, I suggest doing cultures on a regular basis, including sensitivity testing to determine if the antibiotic you are using is effective against the current strain of Salmonella. Also, keep in mind that Salmonella often hides inside of cells, so that even if the antibiotic works well on the bacteria in the lab, it may not work as well in the animal, as certain antibiotics are not very effective at penetrating cells or other places Salmonella may be hiding. Work with your veterinarian to interpret lab results and make the best choice for your treatment regimen.

 

Producer: Our calves are generally sick for three to five days. They usually continue nursing, but it takes two hours versus two minutes to drink a bottle. They lose at least 5 to 10 percent of their body weight while sick. At one month of age, calves look great – fat, vigorous, shiny, and slick.

 

Dr. Thayer: It concerns me that some of the calves are taking a couple of hours to drink their bottles. There are risks of bacterial growth and contamination when the milk sits in a container or bottles for any length of time before being fed to calves. I also recommend that you culture the milk as it comes out of the pasteurizer. Then, culture the milk that is fed to calves directly as it comes out of the bottles. Do both, on a regular basis, to assure adequate pasteurization. Even one day of failed pasteurization can have devastating consequences. Milk is a great media for bacterial growth. Even a miniscule amount of bacteria in the milk will double in quantity about every 20 minutes, resulting in a lot of bacteriain a very short period of time. Instead of allowing the calves to feed for such a long time from the bottle, I would consider tube feeding those calves. Bacterial growth in the milk is less of an issue in the winter than in the summer, but it can be an issue any time if the barn is heated.