Long-Term Study Investigates Differences in Deer Supplements
Reprinted from Livestock Weekly
Internet Edition - March 26, 2009
By Colleen Schreiber
SAN ANTONIO — Raising big bucks is no longer just a hobby; it’s a full-time business, and a big business at that.
And while the basics for raising quality bucks, still apply — age, nutrition and genetics — the toolbox used for applying these basic principles has expanded greatly over the last decade or so. One tool that is now commonplace on many Texas ranches is the practice of using supplemental feed to enhance a deer herd’s level of nutrition.
Donnie Draeger, wildlife manager of the Comanche Ranch in Southwest Texas, offered a detailed presentation on some of the research results of a supplementation study comparing protein pellets to whole cottonseed during the recent Deer Associates meeting sponsored by the Caesar Kleberg Wildlife Research Institute. The supplementation study is part of a much larger, intensive culling study. Other cooperators on the study include CKWRI and Texas Parks and Wildlife.
Before getting into the data, Draeger offered thoughts on the pros and cons of cottonseed and protein pellets.
Cottonseed, the byproduct of ginning, is a proven highly nutritional and highly digestible supplement. It is also typically cheaper than protein pellets in both feed cost and distribution, though admittedly, Draeger said, the last few years the actual cost of the feed has not been that much cheaper.
Comanche Ranch uses a mesh wire type cage as a cottonseed feeder. It costs all of about $10. This type of feeder allows fawn access, but there is still limited use by non-target animals such as feral hogs, raccoons, and the like.
Whole cottonseed is also weatherproof, so it can be stored essentially out in the open. However, there can be combustion problems in the hot South Texas environment.
Additionally, whole cottonseed contains a natural chemical called gossypol, which can be toxic. In one research project, conducted by CKWRI and sponsored by Comanche Ranch, graduate student Sarah Bullock found that toxicity may only be a problem when cottonseed is more than 50 percent of the diet. According to Bullock’s research, deer in her pen trials began to regulate themselves as cottonseed approached 50 percent of the diet.
Like cottonseed, protein pellets range anywhere from 14 to 20 percent protein. Advantages of protein pellets as a supplemental feed are that it is easy to use, and it can be widely and evenly distributed. Perhaps the greatest advantage is that, unlike native vegetation, deer pellets provide a constant level of protein and nutrients year-round, regardless of climatic conditions.
However, like cottonseed, protein pellets also have some limitations. First, they are not cheap. Recent estimates have deer protein pellets averaging $375 a ton in Texas.
Another issue is that protein pellets are also used extensively by non-target animals, so fencing around feeders is recommended. However, this practice in itself creates another challenge in that it limits fawns from accessing feeders.
Additionally, if excessive moisture gets on the feed, a bacterial growth, which can be harmful to deer, can occur. Finally, it is a man-made formula.
“We think this is what deer should have in their diet, but we’re still learning and hopefully perfecting some of that through some of the nutrition work being done by CKWRI researchers,” Draeger said.
The supplementation comparison study is being conducted on the 113,000-acre Comanche Ranch located in Maverick and Dimmitt counties in Southwest Texas between Eagle Pass and Carrizo Springs. It can be a harsh environment with relatively low productivity, given that the annual rainfall averages 18 inches.
At present, the supplementation on the Comanche Ranch is such that there are some parts of the ranch in which deer are supplemented exclusively with cottonseed and other parts of the ranch where the deer are fed exclusively protein pellets; the remainder of the ranch has no supplementation whatsoever.
One big caveat Draeger stressed repeatedly was that they have been feeding protein as a supplement for seven to eight years. Cottonseed supplementation, however, was only introduced three years ago, right before the start of the study. It’s common knowledge that it takes a variable period of time for deer, which are natural browsers, to get used to feeding on protein pellets. The same is true for cottonseed. On Comanche Ranch the feeder density rate for both protein and cottonseed is one feed station to every 200 acres.
Over three years 3838 individual bucks and does were captured using a helicopter net gun. Of that total, 2811 were bucks and 429 of the 2811 bucks were recaptured at some point during the three-year period. Breakout of bucks captured by treatment was 855, 1557 and 658 on cottonseed, protein and no supplement study sites, respectively, over the three-year period. Additionally, 1027 does were captured over the three years.
Each captured deer was given a unique ID number; it was aged, weighed, and all of the Boone and Crockett scoring measurements were taken.
Given the above numbers, the data presented included results from the first three years of what is to be a 10-year study. Draeger broke the results down in several different ways to look at the various pieces of the puzzle from a different perspective.
The first such piece was a comparison of the differences in liveweight of the various age classes of bucks by feed type over the three-year period. For comparison purposes he focused on the 6.5 year-old bucks. To date, protein-fed deer averaged about 184 pounds liveweight while the bucks on cottonseed and even those on no supplement averaged 158 pounds liveweight, a 26-pound difference between them and the protein-fed bucks.
In a nutshell, protein-fed deer were significantly heavier in seven of the eight age classes compared to cottonseed supplemented deer and no supplement. In contrast, on the cottonseed treatment, five of the eight age classes were significantly heavier than the no-supplement bucks.
“Don’t judge cottonseed too harshly yet,” Draeger told listeners. “The first year of data collected was the first time these deer were ever exposed to cottonseed,” he reminded. “Contrast that to protein, which has been fed across the ranch for seven or eight years.”
And, in fact, the data possibly seemed to bear that out. In the first year, there was no significant difference in liveweight between cottonseed-supplemented cohorts and that same cohort on the non-supplemented area. However, by year two there was a significant difference in seven of the eight age classes. In other words, deer on the cottonseed supplement were gaining weight compared to deer in the no-supplement treatment.
One discovery that is somewhat confounding is that weights of cottonseed-supplemented deer became erratic in the five and older categories during year three of the study. In fact, Draeger pointed out that some of the liveweights of cottonseed-supplemented deer for the 5.5-plus age categories were actually lower than the non-treated deer.
“We’re not sure yet what’s happening there,” he admitted.
As for the no-supplement treatment, there was no statistical difference in liveweight across years for any of the age classifications except in the third year. In this year, almost every age class was heavier across the board except for yearlings. Interestingly enough, 2008 was on average a dry year.
“The only rain we received that year was five-plus inches in August,” Draeger said. “The only explanation I can come up with is that the deer, most of which were captured from October through January, were able to make good use of that green-up. But why it didn’t have an effect in the cottonseed pastures or at least didn’t equal the year before, I can’t tell you,” he admitted.
One set of data points that stood out were the yearling weights. Liveweights for protein-fed yearlings were only slightly higher but not significantly different than liveweights of that same cohort on cottonseed and the same cohort on no supplement. It was a trend that Draeger admitted concerned him.
As for the does, they found no clear pattern in terms of differences in liveweight by feed type across the three years. The only aspect that held true, again, was that there was no difference in liveweights of yearling does across the three treatments.
“There was a little help in the protein pastures all the way around, but even in the six and seven year-old does, it’s not real distinct,” Draeger pointed out. “It could be, perhaps, that does meet their nutritional requirements much faster than bucks, or perhaps some were raising fawns during that time and some were barren, and those does could be gaining better than those that have fawns,” he hypothesized.
“The take-home message is that to date, the doe and buck yearlings are not showing any significant difference in weight gain across the three treatments,” Draeger said.
Draeger next offered a detailed look at buck weight loss during the rut across treatments for the three years of the study. The data was broken into two parts — pre-rut and post-rut represented as October though December and January through February.
On the cottonseed treatment, Draeger noted that there wasn’t a big difference pre-rut (October through December) and post-rut (January and February) buck weights across the different age categories during the first year. Actual numbers indicate about an eight-pound loss during the rut for mature bucks on the cottonseed treatment.
However, in the second year, pre-rut weights of cottonseed-supplemented bucks jumped significantly. In fact, the pre-rut weights were close to the pre-rut weights of the protein-fed bucks, and that trend extended into the third year.
He also showed graphs for the unsupplemented deer. In this case, the starting weight (October through December) is much lower compared to the other two treatments during this same time period. However, the ending weight, again, was similar to the ending weight of deer on cottonseed supplement.
Next he showed the data for the protein supplement treatment. Predictably, there was an improvement in pre-rut bodyweights. However, the ending weight on average was relatively the same as the other two treatments.
To sum it up, the actual weight lost during the rut was essentially the same across treatments.
“I think that’s significant,” Draeger says. “It’s almost as if there is a point at which deer decide, rut or no rut, they have to eat something.”
On average, across all treatments bucks lost about 35 pounds during the rut.
“This trend may not hold, but that’s what it’s showing to date.”
The message from that, Draeger reiterated, is that supplemental feeding of any kind does not appear to decrease the percentage of weight lost during the rut.
“Even if you feed protein all year long, your deer are going to lose approximately the same amount of weight as deer on no supplementation. The key advantage to protein is that those deer will be starting and finishing at a higher weight. And, according to our data, most bucks are going to lose about the same amount of weight — somewhere in the 30 to 40 pounds range — regardless of their supplemental source, if any.”
Another piece of the study was to determine what percentage of the white-tailed deer on Comanche Ranch were actually consuming protein. Additionally, they wanted to find out of those eating protein what percentage of the total deer’s diet is actually made up of protein. To answer these questions, Ryan Darr, a CKWRI graduate student sponsored by the Comanche Ranch, learned how to apply a technique that is widely used in other ecological studies to estimate the amount of pelleted feed the deer were eating. It is a complicated process in which stable isotope levels in the protein feed and the native vegetation are compared to those in the tissue of the deer.
In setting up this next set of data, Draeger cautioned listeners to be careful how the numbers are extrapolated. In other words, it shouldn’t be inferred that just because this is what was found on the Comanche Ranch that the same would hold true elsewhere.
“This is a study done on our ranch with our feeding scheme and our feeding intensity levels,” Draeger reiterated. “It may not be applicable to everyone, and certainly I can promise it will be different as feeding intensity differs. So be cognizant of that.”
Before he had the results in hand, Draeger told listeners that he had high hopes that 50 to 70 percent of the deer on the Comanche Ranch were eating protein. The result surprised even Draeger in that it was considerably higher than he expected. In fact, 98 percent of the 192 bucks two years and older that were sampled that had protein available to them were actually utilizing it.
Furthermore, of those eating protein, on average, 60 percent of the deer’s diet was made up of protein feed. That held true across all age classes, excluding yearlings.
Using the raw data, he pointed out another interesting fact. Of the 192 samples taken, 180 deer ate protein feed. Furthermore, of the 12 deer that did not eat protein, 10 were yearlings. In other words, about 26 percent of the yearlings were not eating protein.
“That’s a big deal,” he told listeners. “Now perhaps we can better understand why we didn’t see any difference in yearling buck and doe weights on the protein treatment.”
He broke the yearling data down further by looking at the 74 percent of the yearlings that were consuming protein. Out of the 74 percent that ate protein pellets, protein pellets only accounted for 47 percent of their total diet, which again, he noted, wasn’t enough to really bump up yearling weights.
“That does concern me as a manager, because those fawns and yearlings are the future. Now that we’ve at least confirmed that there is a problem, we’re going to take measures to try and bring the level of protein pellet consumption up.”
In analyzing the yearling data further, they learned that the percent of feed in the yearling’s diet was in fact positively correlated to yearling weight. So just how much of an increase in protein consumption is needed to make a difference in the yearling category? To find out, a formula was developed using a regression analysis. It indicated that every 10 percent increase in protein pellet consumption in a yearling’s diet translated to 3.2 pounds of weight gain.
“That gives us something to shoot for,” Draeger commented. “The more they eat, the more weight they put on, the healthier they are likely to be and the more likely they are to reflect their true genetic ability.”
They also looked to see if deer density had an impact on protein consumption. The data indicated that deer density did not change the amount of protein consumed, at least it was not statistically different. In fact, he noted that most of the 10 yearlings that did not eat protein were actually in the medium density pastures.
The results indicated that individual feed consumption in the low density pasture was higher (68.1 percent) than it was in the medium (52.6 percent) and high density (57.2 percent) pastures, which as Draeger pointed out, is really counterintuitive.
“I came to the conclusion that it probably has a lot more to do with habitat quality than density,” Draeger told listeners.
Another interesting discovery was that the data showed no significant correlation in weight or antler size based on percent of feed in the diet across the different age classifications.
“In other words, once bucks ate protein feed, the amount eaten did not have a significant impact on weight gain or antler size.”
The good news is that the data also clearly shows that protein supplementation works, not only in terms of weight gain but more importantly in antler size. As proof, he broke out data showing protein-fed deer at the various age classes and compared those to deer fed cottonseed and deer in the no-supplementation category. He looked specifically at the mature buck category, bucks 6.5 years of age and older.
“On average, mature bucks scored 14.5 inches higher on the Boone and Crockett measuring system than bucks of the same cohort that were fed cottonseed as well as those that were not supplemented at all. Protein pellets do work, without a doubt.”
As for the cottonseed treatment, he noted that they have not seen an increase in the average gross B&C score. It’s still statistically the same as the no-supplement. However, Draeger once again suggested that it’s a matter of patience.
“I believe that we will see an improvement on cottonseed-supplemented deer, and we will document those improvements as this study carries on. It’s just going to take longer than three years,” he told listeners. “Remember, cottonseed-fed deer were significantly heavier in five of the eight age classes compared to the control, so it is starting to work on the weight side.”
He stressed that weight increases are likely to be seen before improvement in the gross B&C score. And, it’s not an overnight process.
“It’s going to take many years to get there, but you will get there if you have the right feeding intensity and you keep at it.”
In wrapping up his comments, Draeger reiterated that the data presented is site-specific. He also noted that having feeders distributed as evenly as possible across the landscape is important.
“Create an environment whereby the supplemental feed is not a limited resource. That has to come through density of feeders and also persistence of feed. Don’t let feeders run dry, and make sure your feeder density rate is high enough that literally, if a buck walks up to one and he’s pushed out by a dominant buck, it doesn’t take him but five or 10 minutes to walk to another feeder.”
