John Ozoga on summer and fall fawn nutrition

Successful Deer Management Starts With Large Healthy Fawns: Summer and Fall Nutrition

By John J Ozoga

Fawns born to malnourished does weigh as little as 2 pounds at birth, whereas healthy individuals can weigh as much as 12 pounds. Generally, single fawns weigh more than those from twins or triplet litters. However, few fawns weighing less than 5 pounds survive more than a few days, because they are too weak to stand and nurse, are abandoned, or their mothers produce no milk.

At birth, buck fawns tend to be about one-half pound heavier than does among mixed-sex litters. Since their weight differential increases slightly as the mother’s nutritional plane declines, researchers speculate that males are more resistant to prenatal malnutrition.

Deer milk is higher in fat, protein, dry matter and energy content than milk produced by domestic ruminants. The doe’s diet has little or no influence upon the composition or quality of her milk, but poor nutrition may cause her to produce less milk than normal. Or, if the doe is seriously malnourished, she might produce no milk at all.

Given their mother’s good health and a plentiful supply of nutritious milk, fawns gain nearly a half pound in body weight per day during early life. Even those fawns undersized at birth tend to exhibit accelerated weight gain; by 1 month of age there seems to be little weight difference among well fed fawns, regardless of their birth weights.

Young fawns are very efficient in converting nutrients into skeletal and muscle growth, but they lay down little fat until they are weaned. The average fawn may double their weight within 2 weeks, about the time it starts to nibble some vegetation, but cannot survive without its mother’s milk.

To grow properly, fawns require nourishing forage that has from 14 to 22 percent protein content, with males having higher requirements than females. Compared to females, buck fawns appear to be especially sensitive to nutritional shortage during the first 4 months (i.e., summer).

The capacity and function of the fawn’s rumen-reticulum increases as the fawn gains weight. When fawns are 5 or 6 weeks of age and weigh about 25 pounds, their forage intake increases substantially. Fawns older than this can compensate somewhat for decreased milk intake by eating more vegetation. Although they can survive, when maternal nutrition is poor and the doe’s milk supply is limited, fawns undersized at birth will also be undersized at weaning age.

Autumn Requirements

Although dietary protein content may be more important than the amount of energy in the fawn’s summer diet, digestible energy needed for fattening becomes more important during autumn. Normally, fawns don’t lay down appreciable fat until October, with peak fat reserves not accumulated until mid-December. Also, female fawns tend to be fatter than buck fawns in autumn.

Our studies at the Cusino Wildlife Research Station revealed that 10 weeks of inadequate autumn diet (October throughout mid-December) stunted fawn growth, but the sexes seemed to suffer equally. Autumn food-deprived fawns grew more slowly and stored less fat than well-fed ones. However, even those fawns on poor or marginal autumn range store appreciable fat.

Therefore, it appears that deer inherently are compelled to store fat in autumn, while sacrificing body growth if need be.

In other words, well-fed fawns tend to be skeletally large as well as fat. By comparison, malnourished individuals might be fairly fat, but stunted. Also, based on our studies at Cusino, when provided an unlimited supply of browse, stunted, lean fawns can survive winter by consuming more browse, feeding more efficiently and minimizing their activity to conserve energy.

In a special study, we examined the effects of diet quality by feeding two levels of protein and energy during a 10-week autumn period. Differences among the diets were produced by varying the proportions of ingredients to provide either 16.2 percent or 6.6 percent protein along with 3,000 or 2,700 kilocalories of digestible energy per kilogram of pelletized feed – hence, 4 different diets.

At the end of these trials, fawns receiving the highest energy diets were 4 to 10 pounds heavier and stored roughly twice as much fat, as compared to those on low energy diets, regardless of protein intake. These heavier animals also showed the greatest hind leg growth and longest legs when the study was completed.

We concluded that a rich protein diet is not vitally important in the young whitetail’s autumn diet. However, even a small shortage of digestible energy can be detrimental.

In my studies, conducted with an enclosed population of supplementally-fed deer, does achieved about 88 percent of their skeletal growth (as determined by hind-foot length) by 7 months of age, compared to 85 percent for bucks, but only 52 percent and 43 percent of their mature body weight, respectively. As yearlings (1.5 years-old), bucks and does attained 98 percent of their skeletal growth and slightly more than 80 percent of their mature weight.

It’s important to note that bucks accomplished most of their skeletal growth before they disperse from their natal range at yearling age. This indicates that habitat preferred by matriarchal groups (doe groups) for fawn-rearing might ultimately determine a buck’s physical size at maturity – regardless of nutritional conditions on his newly established range.

Literature Cited

Ozoga, J. J. 1988. Incidence of “infant” antlers among supplementally-fed white-tailed deer. Journal of Mammalogy 69: 393-395.

Ozoga, J. J. and L. J. Verma. 1982. Physical and reproductive characteristics of a supplementally-fed white-tailed deer herd. Journal of Wildlife Management 46:281-301.

Ozoga, J. J. and L. J. Verma. 1984. Effects of family-bond deprivation on reproductive performance of female white-tailed deer. Journal of Wildlife Management 48:1326-1334.

Ozoga, J. J., L. J. Verma and C. S. Bienz. 1982. Parturition behavior and territoriality in white-tailed deer: impact on neonatal mortality. Journal of Wildlife Management 46:1-11.

Verma, L. J. 1988. Lipogenesis in buck fawn white-tailed deer: photoperiod effects. Journal of Mammalogy 69:67-70.

Verma, L. J. and J. J. Ozoga. 1980. Influence of protein-energy intake of deer fawns in autumn. Journal of Wildlife Management 44:305-314.

Verma, L. J. and J. J. Ozoga. 1980. Effects of diet on growth and lipogenesis in deer fawns. Journal of Wildlife Management 44:315-324.

Verma, L. J. and J. J. Ozoga. 1987. Relationship of photoperiod to puberty in doe fawn white-tailed deer. Journal of Wildlife Mammalogy 68:107-110.

Image IMG_1433.JPG Caption: Fawns receiving adequate nutrition are able to build greater skeletal mass and fat reserves before winter hits.