Wednesday, November 30, 2011

Are Southern Deer Genetically More EHD Resistant?

EHD Resistant Southern Deer????
I keep seeing things about 'buy my deer because they are EHD resistant southern deer'. Everyone can have an opinion on something but when it's controversial sometimes people get a little overzealous in their arguements. I'm a scientist, not a mad scientist, and not one in a lab with bubbling bottles. I was trained as a wildlife biologist and studied deer behavior for two masters degrees. That doesn't make me smarter than anyone else but that much education does make your mind look at things a little differently.
In a scientific study, all variables not being manipulated for research should be controlled. For example, if I had two groups of deer in my study to determine if protein supplements produced bigger antlers and one group was my 'control' that didn't recieve the supplement but they had a food plot with high protein beans and the group that received the supplement had bermuda grass, then it wouldn't be a good scientific study because the variables in the food plot would make the study inaccurate.
A lot of what you hear about deer health and what works is anecdotal evidence. Anecdotal evidence is not scientific in nature. An example would be if I put vanilla extract in my deer water when they had pneumonia and they all got well, then vanilla being the cure for pneumonia would be anecdotal evidence. They may just have gotten over it on their own.
'Facts' that you hear about EHD resistance in deer is often anecdotal. There is some evidence but not much that proves a southern deer may be inherently more EHD resistant than a northern deer because of years of breeding to only southern deer. I haven't found the study again yet but I had read one a couple of years ago and if I do find it again I'll post it. The study was on passive immunity for EHD and I think southern deer were used. The study took a group of fawns as newborns to bottle feed. Titer levels were checked and found there was some EHD resistance. That was from passive immunity from the mother either through the placenta or immunoglobins in the cholostrum.
The fawns were divided into two groups. One was left outside and the other was moved inside to an insect-free environment. At weaning the two groups were checked for titer levels for EHD resistance again. The outside group showed resistance but the inside group did not. The results of the study showed that resistance exists from passive immunity when born but the passive immunity does not relate to permanent immunity. The difference in the two groups of fawns is that the outside group had exposure to the virus but the inside group did not. EXPOSURE is necessary either through direct exposure to the virus in the environment or through vaccines. Otherwise, after the passive immunity wears off the animal will be unprotected.
If the animals were EHD resistant because they were from the south and it was in their genetics passed down, then the EHD would have been there after weaning for both groups. The arguement is that if you buy northern deer and move them to the south, they won't survive. I have about 300 pure northern genetics deer in Louisiana. Did I lose many when I moved them here? You bet. I got sick of going out and dragging dead deer to my burn pile. The southern resistance guys will say that mine died because they weren't EHD resistant or weren't used to our insects or other diseases. I agree in part, but.....when deer are handled, they are stressed. If they are darted they are stressed even more. A study in South America on red deer showed lack of immune response 30-40 days after tranquilization. Hauling deer in a trailer for 20+ hours adds to the stress level they already have. Then you dump them out in foreign surroundings often mixed with deer that start pecking order fights. They are put abruptly on new feed. It's no wonder so many die. And stress doesn't just last 2-4 weeks. Some studies indicate that stress related illnesses can occur up to a year later.
I believe that moving northern deer south will result in some deaths. Minimizing stress through proper handling will help a great deal. Bringing feed from their origin and gradually changing the ratio of new/old feed will be less stressful. Pen size changes can cause stress. I use Aureomycin in my feed for a month after the deer are moved. Anything to mitigate the changes and stress that results from it will increase survival rates.
As for EHD, I believe that northern deer can survive very well in the south. They must have some exposure to the virus. There will be deaths. But, I know of many pure southern deer that have died from EHD. Ask a biologist from any southern state when there is a bad epidemic of EHD. Native deer are dying in the woods.
If you move northern deer south, just prepare for higher death rates. Once they get past that first year they do much better. The offspring don't know the difference. The advantages of northern bloodlines are worth what we went through initially. If you don't want that heartache and stress, buy northern bloodlines from someone who has suffered through it and has the strongest survivors.
EHD and BT viruses are killers no matter where the deer are from when it hits hard.
Please respond with your comments. I know there will be a lot of you that feel differently but at least try and find some scientific evidence to back up your arguements.

1 comment:

  1. Hi Charles,
    While I agree with some of your theories, I don't agree with all of them. I believe stress levels play a huge role in allowing inherent resistance to be expressed. You can be resistant to any vast number of bacteria and viruses but if your stress levels are such that your body and immune system are rundown then you will develop the illness regardless of titers and this is how I believe wild southern populations die during outbreaks. When do outbreaks typically occur? That's right late August when sweltering heat coupled with nutritional stress in populations over the carrying capacity and during a time where does have fawns pulling on them. Bubonic plague killed much of Europe, however when the plague reached a large enough number of people, some survived and later research determined these people carried a unique genetic marker. While the study you reference sounds valid, small sample size might have been a factor in not being able to cast a net large enough to collect some that are resistant. I reference a situation at MSU whitetail research pens under Dr. H. Jacobson (personal communication) where Ehd/BT hit during a translocation study where a group of Michigan deer in Mississippi died at an 80%+ clip, crossbreeds died in 50%+ range and guess what? The pure Mississippi deer died at about a 12% rate. These deer comingled under the exact same conditions. Could heavier body weights and other attributes that make living in the North easier have been the extra straws of stress that broke the camels back or did inherent resistance play a role? If not, explain what led to the crossbreeds higher level of die-offs compared to full southerns? I don't have the answers, but what I do have is a Southern herd that in my worst year lost 12, 4 does and their young twins, while 10 miles north and 40 miles south lost in the 60's for a mortality percentage that was 5 to 1 compared to mine and I have raised deer since the mid 80's and I don't vaccinate, spray, or fog. This is not to say I don't think northerns can develop resistance, as they obviously can. I just believe that given the same set of conditions, endemic southerns will survive at a much higher rate. Sometimes anecdotal evidence and previous experiences are all we have to go on. Wouldn't it be neat to see an extensive study that involved testing all of these theories as well as if the vaccines really work? Best Wishes.