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Thread: Rate of Temperature Drop in Big Game Animals

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    webmaster Michael Strahan's Avatar
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    Default Rate of Temperature Drop in Big Game Animals

    Hi folks,

    I'm working on a project and am wondering if any of you have captured data on the rate of post-kill body temperature drop on big game animals up here? If you are preparing for a hunt this fall and would not mind the additional hassle, would you mind taking a few readings for me? All you need is a meat thermometer and a notepad. Here's what I need:

    1. Strip off a small chunk of hide on the biggest part of the hindquarter and plunge a meat thermometer in as deeply as possible into the quarter as soon as possible after the animal is dead. Record the temperature.

    2. Record a reading of the ambient air temperature.

    3. Take similar temperature readings every hour until the base temperature remains constant.

    It would be great if we could do this with a bull moose and with a caribou, but I'll take what I can get. Thanks to anyone willing to help with this!

    Regards,

    -Mike
    LOST CREEK COMPANY: Specializing in Alaska hunt consultation and planning for do-it-yourself hunts, fully outfitted hunts, and guided hunts.
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    Forum Admin Brian M's Avatar
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    We talk about this in my forensic science courses, as body temp can be important in determining time of death. In humans, the rate of algor mortis (body cooling) is 1.5-2 degrees F per hour. This can be altered by a number of factors, though. I'd be curious how that rate differs in animals.

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    webmaster Michael Strahan's Avatar
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    Quote Originally Posted by Brian M View Post
    We talk about this in my forensic science courses, as body temp can be important in determining time of death. In humans, the rate of algor mortis (body cooling) is 1.5-2 degrees F per hour. This can be altered by a number of factors, though. I'd be curious how that rate differs in animals.
    I know that ambient temperature plays a huge role, and would assume ground temperature and wind would also make a difference. And of course I would expect the rate to decrease with game animals (compared with humans), due to thick coverings of hair. I'm not looking for a precise controlled environment situation so much as a general idea.

    -Mike
    LOST CREEK COMPANY: Specializing in Alaska hunt consultation and planning for do-it-yourself hunts, fully outfitted hunts, and guided hunts.
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    Member TWB's Avatar
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    Default Rate of Temperature Drop in Big Game Animals

    My experience...

    To get a moose from kill site to at or below 50 degrees, it will take roughly 9 hours. Ambient was 39* clear skies, sunny. TOD roughly 2030, temps did drop over night.

    On another, it took 16 hours to get at or below 50*. Ambient roughly 44, cloudy. TOD 1030, had a warm afternoon but I don't believe it passed 50*.

    These are my recounts just from quick temp checks, not a log or anything I did.

    No accounts of temps at time of kill.

    Biologically, moose have a body temp of 101-102 based on a study I read from Michigan State regarding Shiras moose.

    Some will take longer. Quarter thickness, physical activity, ambient will alter results.

    No sure from a chemistry level if pH levels will slow/speed cooking of game meats.
    We do not go to the green woods and crystal waters to rough it, we go to smooth it. We get it rough enough at home; in towns and cities; in shops, offices, stores, banks anywhere that we may be placed

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    Default hide

    Quote Originally Posted by Michael Strahan View Post
    1. Strip off a small chunk of hide on the biggest part of the hindquarter and plunge a meat thermometer in...
    Taking that hide off completely allows the meat to attain ambient temp much faster (better meat care). Or, maybe in your directions, that first temp check needed to happen right away, before skinning him, and the rest subsequent to that?

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    Quote Originally Posted by Brian M View Post
    We talk about this in my forensic science courses, as body temp can be important in determining time of death. In humans, the rate of algor mortis (body cooling) is 1.5-2 degrees F per hour. This can be altered by a number of factors, though. I'd be curious how that rate differs in animals.
    At first I was thinking "but you usually don't skin a dead person.....usually" so it might be faster.....but then again even with the skin off, humans don't have 130 pound back hams......well most don't anyway (we'll leave my mom's side of the family out of this)

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    webmaster Michael Strahan's Avatar
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    Quote Originally Posted by FamilyMan View Post
    Taking that hide off completely allows the meat to attain ambient temp much faster (better meat care). Or, maybe in your directions, that first temp check needed to happen right away, before skinning him, and the rest subsequent to that?
    The reason for that part of the instruction is because we need a reading right after death, and the hide on a hindquarter can be 1/2' thick. I want the temperature probe to get as deep as possible. If we wait until the quarter is skinned, it could be an hour. The average basal temperature of a live moose is around 102F*, but it spikes immediately after death. That number becomes the beginning point of the chart.

    -Mike

    *Source: A. W. Franzmnn, "Baseline body temperatures, heart rates, and respiratory rates of moose in Alaska", Journal of Wildlife Diseases 20:333-37, 1984. Actual number Franzmann quoted was 38.7C (101.66F).
    Last edited by Michael Strahan; 10-06-2013 at 12:53.
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    Question normal moose temp

    Quote Originally Posted by Michael Strahan View Post
    ...temperature of a live moose is around 102F, but it spikes immediately after death.
    I had no idea that was so; thanks; I'd have thought it was a certain temp without a spike at the end. Do you know if that end of life temp spike pertains to both the moose who never saw it coming, and the moose that was adrenalined up, running for its life when it ended?

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    Yeah, I don't know either.

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    I could talk (or write) all day long about data I've collected on temperature related spoilage factors. If you need specs, here's a quick theory I've worked with for many years:

    1. Time of death on moose and caribou: 101 degrees F by anal temperature (varies very little beyond .5 degrees F). Deep tissue still remains around 101 degrees F.

    2. Hide on post death for two hours, deep tissue climbs to 101.8-102.2 with ambient temps less than 60 degrees F.

    3. It requires removal of large qtrs and neck meat for temperature variance to alter post-harvest. By my tests with careful scrutiny, expect 24-36 hours post dismemberment to render deep tissue core temps to below 50 degrees with ambient temps consistently less than 50 degrees (38-48 degrees F). The caviat to this core temp reading is how much airflow was provided, how much shade, how much surface cooling allowances via water/airflow.

    4. Cooling deep tissue core temps to below 50 degrees (46-49 degrees) in less than 12 hours for a hind qtr requires specific measures for rapid cooling, such as water immersion therapy for 5-7 hours in 24" depths of moving water (1-3 mph current) at an average water temp of 43 degrees F.

    5. careful handling in cooler ambient temps (late season hunts) to prevent cold shortening should be a priority. If ambients temps are 25-30 degrees F for extended periods, it will take about 16-18 hours for the deep tissue temperatures to read 34-38 degrees F. In these scenerios and to prevent cold shortening, I would immediately immerse game meat in river or lake water (base temperature storage would be expected between 39-42 degrees F). This will prevent tissue freeze and reduce the likelihood of cold shortening prior to rigor mortis. This is especially important for the first 38-48 hours post harvest. After 48 hours, most animals have completed the process of glycolysis and muscles have balanced the chemistry requires to render sugars to acid, which is the base requirement for aging game meat. If muscles are allowed to freeze before 48 hours, the result would be catastrophic to tenderness (resulting in cold shortening).

    Last note: On an average hunt with temps ranging from 30s F to high 40s F daytime and 30s-40s nighttime temps, provide overhead protection from moisture and plenty of airflow...then expect 30-40 hours to reach deep temps in the low 50s to mid 40s F. After that, hunters who keep meat cool and dry and well shaded during daytime can expect to see 38-45 F deep tissue readings after 48 hours with ambient temps in the 40s and nighttime temps in high 30s or less.

    All info above is relevant to ambient temps, airflow, shade, and moisture control. I make no promises of the hands on techniques other apply, these are just my observations and practices.

    I'll make a youtube video in the next couple of weeks that show some of these findings and practices on moose I cared for this year. I'll post the link here when its done.

    Larry

  11. #11

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    Very interesting stuff, Larry. I hadn't heard of "cold shortening" before. I guess I've just been lucky enough to shoot animals with warm enough temperatures to prevent that (but cool enough and processed fast enough to avoid spoilage). Now I know to be careful on both ends of the temperature scale.
    Jason
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    Mike, a couple of temperature related points you might want to factor in to your "basal" charting:

    1. Anal temperature is likely the most accurate and most reliable method for charting the animal's "core temp" immediately at the time of death.

    2. The animal's liver temp is important for charting the knowledge of time of death, which is technically the starting point for accurate post mortem bacterial threats related to temperature (bone sour). But this information becomes useless once the hide is removed and parts dismembered from the carcass. This is important when you're trying to understand bone sour related to a carcass that was lost and found and recovered many hours after harvest...

    3. Deep tissue readings must be differentiated by "facing side" reading and "ground side" reading: The facing side hind-leg deep tissue reading at the time of death will equal the ground side for about half-hour, and then your threat-scale data separates in accuracy as the ground side deep tissue retains heat while the facing side quickly loses heat during dismemberment. So, if you're trying to accurately chart the bacterial threat related to spoilage, your data become drastically ambiguous if temperature is your basal calibrator.

    4. Your data are virtually useless if you're trying to specifically target spoilage threats, and here's why:

    A. A clean piece of meat without bone-in (neck) which has a deep tissue reading of 100 degrees F will keep longer than a clean piece of meat the same density with a bone-in (hind qtr) at 100 degrees F.

    B. The same cuts of meat as above which have been carelessly handled (dropped in ground dirt, urine, blood, blood shocked tissue, or any other source of bacteria) which also has a deep tissue reading of 100 degrees F, will spoil exponentially faster by the hour due to introduced bacterial colonization (surface bacterial invasion).

    C. The same cuts of meat as the above scenario (# B) will preserve exponentially longer than A or B if deep tissue temperature during the first 4 hours drops to below 50 degrees F and remains there during test study.


    So, keep in mind that while temperature is one critical factor to understand (and chart) spoilage threats, data charts are useless unless you are working with known types and quantities of specific spoilage threats (bacteria, damaged tissue, bile, urine, feces, contaminants, soil, wound drainage, etc.). The lists of spoilage threats are simply so very complex and difficult to pinpoint, that your suggested temperature charts are virtually a waste of time compiling and using.

    In short, while you may be wanting to impress yourself or others with discussing the issue of temperature related meat spoilage...your data and presentation runs the risk of overlooking impossible determining factors of source contaminants, handling practices, time sequences and temperature flux, field storage time and conditions (air, moisture, and temp variables), and other factors like types of storage bags used from one study to the next, or exhaust absorption odors from motorized transports. Discussing temperature as it relates to game meat spoilage is conjecture without known quantifiable variables that determine the actual rate and spread of bacterial colonization.

    I hope all of this makes sense.

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    webmaster Michael Strahan's Avatar
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    Quote Originally Posted by Troutnut View Post
    Very interesting stuff, Larry. I hadn't heard of "cold shortening" before. I guess I've just been lucky enough to shoot animals with warm enough temperatures to prevent that (but cool enough and processed fast enough to avoid spoilage). Now I know to be careful on both ends of the temperature scale.
    Trout,

    Cold shortening is well-known in the commercial meat packing industry, and I have done a bit of research on it in preparation for seminars I teach on meat care.

    Cold shortening results from meat cooling too fast before rigor mortis fully sets in. It's not as common with larger animals such as moose or bison, because the large muscle mass involved usually precludes premature freezing. It's not as common with Dall sheep, primarily because most sport hunting for sheep occurs earlier in the year when ambient temperatures are consistently well above freezing. We see it mostly with caribou; particularly caribou taken in the northern half of the state, after the middle of September, when temperatures can consistently remain below freezing for hours on end. I've been teaching this in my meat care seminars for many years, and wrote briefly about it in "Float Hunting Alaska's Wild Rivers".

    Cold shortening causes muscle tissues to contract and the meat becomes really tough. The best example of the prevention of cold shortening is from a friend of mine named Doug Drum, who owns Indian Valley Meats, south of Anchorage. He was in the Chukchi region of Russia, just across the pond from us, several years ago. He was there to observe local meat care practices and to assist the Chukchi by providing recommendations that would help them preserve meat for longer periods of time. At any rate, on one of his earlier trips there, he observed the processing of several reindeer during winter temperatures. The animal was butchered and left outside overnight to freeze. The next day the meat was chunked up and shared around the village, but it was characteristically tough. Dough offered to butcher one of their animals and they agreed. So after the animal was killed, gutted and skinned, he covered the meat with the hide and buried the entire cache in the snow. They dug it out the next morning and only the ends of the shanks were frozen, with the rest of the meat nice and cool. The locals cut it up and when they ate it, they were amazed. They nicknamed Doug, "the man who makes summer deer". The meat was as tender as those killed in August.

    I did a hunt on the Noatak in 1992, and we experienced cold shortening. The Noatak was running slush, with ice shelved out from both banks about fifty yards in places. Temps were about 20F at night, and remained below freezing during the day. We killed a few caribou on a gravel bar and laid the meat out to cool as we normally would, but the next morning when we went over to pack it to camp, it was all frozen solid.

    Larry's method of putting the meat in the river could stall cold shortening by maintaining an ambient temperature above freezing. I think the hide could probably do the same, without getting the meat wet. Either way, the trick is to prevent the core temperature from falling below 59F before rigor mortis fully sets in.

    There's a lot more to the science of this, but that's a bit outside this discussion. In most cases, hunters don't have to worry about cold shortening, however they should be aware of it, and how to prevent it in the field.

    Regards,

    -Mike
    LOST CREEK COMPANY: Specializing in Alaska hunt consultation and planning for do-it-yourself hunts, fully outfitted hunts, and guided hunts.
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    webmaster Michael Strahan's Avatar
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    Quote Originally Posted by Larry Bartlett View Post
    ...In short, while you may be wanting to impress yourself or others with discussing the issue of temperature related meat spoilage...your data and presentation runs the risk of overlooking impossible determining factors of source contaminants, handling practices, time sequences and temperature flux, field storage time and conditions (air, moisture, and temp variables), and other factors like types of storage bags used from one study to the next, or exhaust absorption odors from motorized transports. Discussing temperature as it relates to game meat spoilage is conjecture without known quantifiable variables that determine the actual rate and spread of bacterial colonization...
    Hello Larry,

    I'm not sure what happened here, but I did not indicate my purpose for collecting this information, nor am I seeking to impress anyone with anything. I am simply attempting to obtain information from hunters in the field. To clarify, it has nothing to do with spoilage (though it could be used to illustrate the necessity of using preventive means where bone sour is a risk); an issue which is discussed on our Meat Care Page.

    As a separate topic, the causes of meat spoilage are many, as you indicated. Contamination from surface bacteria, dirt, hair, exhaust fumes, or animal fluids, while important, are outside the scope of my question.

    Regards,

    -Mike
    LOST CREEK COMPANY: Specializing in Alaska hunt consultation and planning for do-it-yourself hunts, fully outfitted hunts, and guided hunts.
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    I read larry's post as "you" meaning - any of us - not specifically targeting Mr. Strahan of Billy Jo Jim Bob. I sensed that it also may have pointed to himself a little bit too. Been wrong before though.

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    yep Bullelkklr, it is hard to be frank online when your name is larry...LOL

    When i first began the process of compiling data for Project Bloodtrail, my science of bacterial spoilage always pointed to temperature as a bases for growth speed. I realized after much due process that temperature is only ONE contributing factor in meat spoilage, albeit a major contributor. And rates of cooling deep tissue meat parts varies so widely that a layperson asked to obtain field readings without A LOT of knowledge of data collection and meat handling would be futile and embarrassingly unprofessional if "one" tried to use that data for "ones" professional purpose.

    My point was merely a suggestion that meat core temp rates of cooling are largely irrelevant unless charting very specific temperature variances and moisture variables and time tables and source bacterium and handling practices and so on.

    maybe I got tunnel vision with your "project" focus and assumed you were interested in spoilage variables. Sorry to offend.

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    I have experienced cold shortening and it can happen quick. I killed a caribou on the slope at the end of October 2011 and it was late afternoon and dark by the time I got to the truck. It was frozen solid by morning. That caribou was really tough, but tasted good.

    The next year we went back and this time I took and put all the meat in a cooler with no ice. It was below zero at night and hovered around zero to slightly above the next day. The meat stayed cold but didn't freeze and it was much more tender.

  18. #18

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    Mossyhorn, good tip to prevent cold shortening.

    One other tip is to dismember the animal's qtrs and leave the hide on the legs, then tarp it immediately to preserve the heat retention. If temps are below 20 degrees to 0 degrees F, this works well with no threat of deep tissue bone sour. This at least gives you time to get the animal transported out of the field into more reasonable processing temps.

    larry

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