Q&A with Dr. Harry Jacobson on GAW’s Pellet Formulation

Source: Dr. Harry Jacobson

Q&A with Dr. Harry Jacobson on GAW’s Pellet Formulation

1.) Why is the fiber so high?

Fiber is a neglected nutrient in most commercial deer rations. Low fiber and high concentrate diets can be very damaging to normal ruminant health. Fiber is composed of the cell wall of plants and consists of cellulose, hemi-cellulose and lignin. Fiber in the diet provides a continuous source of fermentable carbohydrate materials to ruminant microorganisms and improves overall utilization of the diet. In normal cases, this means a slow passage of feed, not the rapid passage resulting with a low fiber diet. Fiber is also the primary source of acetic acid in the diet of ruminants and acetic acid provides nearly half of milk fat. Thus for lactating does, fiber is very important in the diet.  A rule of thumb for ruminants is that it should be no less than 16% crude fiber. Fiber is also the reason ruminants chew their cud. If diets are composed of concentrated feed, then cud chewing is reduced. The microorganism production is also reduced, and low fiber leads to less saliva production. Rumen acidosis, damage to the rumen wall, founder, and occasionally polioencephalomalacia can result from rumen organism imbalance and vitamin B deficiency in rumen synthesis. In the best case, founder or polioencephalomalacia may not result, but when animals that have been raised on low fiber diets are released into the wild, they are unequipped for normal survival. They often have poor rumen papillae development, damage from rumen acidosis, and low rumen faunal diversity and capacity. In short, without adequate fiber, deer are fed a supplemental diet they were not evolved to digest, and no longer function as the wild ruminant they evolved as.

2.) Some commercial deer diets show much higher fat content than white-tailed essentials. Why don’t you recommend higher fat levels?

Like everything else in the world of promotion of a product, the sales pitch always seems to be, “if a little is good, a lot has to be better.” High fat levels change energy and protein ratios, so if you increase fat, you also need to increase protein levels. Additionally, it has been shown in dairy cattle that if you increase fat, you also need to increase dietary fiber, calcium and magnesium levels to compensate for imbalances that occur. Upsetting rumen fauna by nutrient imbalance is always a risk, and elevating the level of one nutritional aspect isn’t wise. I have consistently fed and recommended 2-4% fat in the rations I have provided captive and wild deer over the last 30 years. With high performance of these animals shown through body weight, antler growth, and reproduction, I have never encountered a situation when the ration did not meet energy requirements of the animal.

3.) Why aren’t the calcium and phosphorus levels higher?

Calcium and phosphorus requirement of white-tailed deer is one area that has received major research. The highest calcium level requirement reported in a study is 0.55% for does in late lactation. Although it is easy to think that since antlers have high calcium levels, high calcium levels are important for antler production. Actually, antler growth requirements for calcium are only 0.17% of the diet; 1% calcium diet is well above all known calcium requirements. Conversely, high calcium levels (1.5%, or above) are dangerous to does, and they can come down with milk fever shortly after birthing. In the early years of my research, I had personal experience with milk fever while feeding captive research deer a diet that was too high in calcium levels. Essentially, deer that are fed supplements with high calcium levels become dependent on external sources of calcium and “forget” how to manufacture calcium from their own bone reservoirs when faced with the high demand for calcium at the time of birthing.

Phosphorus levels also have been studied in great detail for white-tailed deer. The highest reported literature values were for lactating does, and these were 0.5%. However, for growth, antler development, and maintenance, above 0.17% phosphorus appears more than adequate. In my own work, I could not produce any difference between twin fawns fed a 0.28% phosphorus diet and their siblings fed a high 0.56% diet of phosphorus. In a second experiment, I could not produce any difference between deer fed 0.19% or 0.28% phosphorus.

The bottom line, more is not better.

4.) What scientific studies have actually been done on diet requirements for deer?

The most complete review of current scientific knowledge of nutritional requirements of white-tailed deer is given by Dr. David Hewitt.1 However, the most extensive nutritional studies on deer were conducted over 40 years ago by pioneering deer researchers. Pennsylvania State University published one of the earliest studies of white-tailed deer nutrition requirements.2  The most complete nutritional studies were conducted in the 1960s in Michigan by researchers from Michigan Department of Natural resources and Michigan State University. These researchers formulated a ration based on several years of research on captive deer.3 The ration they developed was later given an extensive test on wild deer in the upper peninsula of Michigan by DNR researchers who documented it’s adequacy for improving nutritional condition of deer in a one mile square enclosure.4 Although additional research has been conducted on protein, and energy requirements of deer, they have not changed or altered the basic adequacy of the diet tested by these earlier studies. The basic formulation of the existing Garland Whitetail Essential ration is, in fact, close in consistency to the proven Michigan ration, with some minor alterations based on more recent research and findings from my own work with both captive and wild deer over the last 40 years.

  1. Nutrition, pages 75-106. In: Biology and Management of White-tailed Deer, 2011 CRC Press, Taylor and Francis Group, NY
  2. French, C. E., L.C. McEwen,N.D. Magruder, R.H. Ingram and R.W. Swift. 1956. Nutrient requirements of white- tailed deer for growth and antler development. J. Wildlife Management20:221-232.
  3. Ulrey, D.E., H.E. Johnson, W.G. Youatt, L.D. Fay, B.L. Schoepke, and W.T. Magee. 1971. A basal diet for deer nutrition research. J. Wildlife Management. 35: 57- 62.
  4. Ozoga, J. J. and L. J. Verme. 1982. Physical and reproductive characteristics of a supplemental fed white- tailed deer herd, J. Wildlife Management 46: 281-301.
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