| White-Tailed Deer/Fat Deposits |
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White-Tailed Deer:
Their Foods & Management in the Cross Timbers
Table of Contents & Preface
Introduction
Habitat requirements
General concepts
Food requirements
Methods
used to gather data
Overall
use of forage classes
Seasonal
use of forages
Specific
seasonal deer diets
Spring
Summer
Fall
Winter
Summary
Cover requirements
Water requirements
Space requirements
Habitat management
General concepts
Food management
Cover management
Water management
Space management
Population health/evaluation
Introduction & aging deer
Body size & antler characteristics
Fat deposits
Reproductive success
Population management
Introduction
Population inventory
Harvest
records
Deer
surveys
Population regulation
Potential
mng't goals
Appendix A:
Plants of the NFWU
Appendix B:
Deer diets on the NFWU
Appendix C:
Pictures and descriptions of
important deer food plants in the
Cross Timbers region
Glossary for Appendix C
Population Health and Evaluation:
Fat Deposits
Fat deposits have always been used by hunters in a qualitative manner. Many hunters have been heard saying "that old doe sure is fat." However, to be of value as a health index, fat deposition must be properly quantified and interpreted. The kidney fat index (KFI) is easily measured using a triple-beam balance or a food scale. Remove both kidneys, with attached fat, from the rear of the stomach cavity prior to gutting and freeze them in a labeled plastic bag until you have time to process them . Trim and discard excess fat from the ends of the kidneys (Figure 6). The remaining fat can be removed and collected by cutting into the capsule or covering of the kidney and peeling it off with fat attached. Record the weight of both kidneys as well as the weight of fat from both kidneys. The KFI is calculated by dividing the weight of the fat by the weight of the kidneys and multiplying by 100. The KFI should not be used to compare health between different times of the year, such as between spring and fall. If animals are gutted prior to processing by a technician, then the depth of back fat can be measured. Make a 2-inch incision through the skin and fat just forward from the base of the tail. Measure the thickness of the fat located between the skin and the meat using a thin, precisely labeled ruler.
The function of fat deposition in deer must be understood to properly interpret population health based on fat indices. The primary function of fat deposition is the storage of energy reserves during a period of relative energy surplus for use during subsequent periods of relative energy deficiency. These periods vary dramatically between the sexes because of the dramatically different seasonal physiological demands placed upon each sex. For example, fat deposition can begin during summer in bucks but may be delayed 2 to 3 months in does because of the extreme energy demands placed on does by lactation.
Evaluation of population health between different times of year using fat indices must be done with caution because of the normal seasonal changes in fat deposition taking place within deer. Internal physiological mechanisms turn the fat deposition process off and on at stategic periods to insure the long-term survival of the deer population. Quantities of deposited fat must be interpreted relative to the seasonally appropriate amounts to be expected under various nutritional conditions. The most appropriate application of fat indices is interpreting area differences within the same season and year or yearly differences within the same area and season.
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