Milk Consumption and Weight Gain of White-Tailed Deer

Feeding trials were conducted with captive, white-tailed deer (Odocoileus virginianus) fawns to estimate the milk requirements of fawns and the requirements of lactating females for milk production. The growth rates of two groups of bottle-fed fawns consuming milk with a composition similar to whitetailed deer milk were compared to fawns raised by captive, white-tailed deer females. Maternal-nursed fawns gained 243.7 -+19.2 g/day. Similar rates of gain occurred in bottle-fed fawns. Bottle-fed fawns receiving lesser amounts of milk maintained a high rate of gain by increasing forage intake. Gastro-intestinal tract capacities were measured to determine relative changes as the fawns became functional ruminants. J. WILDL. MANAGE. 39(2):355-360 The estimation of productive requirements for lactating white-tailed deer females and of milk intake by fawns is dependent upon approximations or measurements of the chemical composition of the milk and the amount of milk produced. The composition of white-tailed deer milk throughout lactation has been measured by Ruff (1938), Murphy (1960), Silver (1961), and Youatt et al. (1965). It is, in general, higher in fat, protein, dry matter, and energy content than the milk of domestic ruminants. Milk protein and fat content change very little during early lactation, but milk fat increases approximately two-fold during very late lactation (Ruff 1938, Murphy 1960, Silver 1961). Milk production of mammals has been estimated by several methods, such as milking of the lactating female, weighing the suckling before and after nursing, or measuring the dilution of body water in the young animal by the known water content of ingested milk (McEwan and Whitehead 1971). Milk production has not been measured in white-tailed deer because of problems in conducting such experiments. Estimates of milk production will vary because of changes in production associated with nutrition, stage of lactation, number, size, and ex of the animals sucking, and age a size of the lactating female. Moen (1973) calculated milk production of whitetailed deer females on the basis of fawn requirements and the physiological and morph lo ical development of their gastrointestinal tract. Milk production of lactating white-tailed deer females was estimated during this study by comparing the growth r sponses of white-tailed deer fawns raised by captive, lactating females to fawns that were bottle-fed specific amounts of milk having the approximate composition of deer milk. Young fawns are able to adapt to variations in milk production by increasing forage or dry feed intake (Nordan et al. 1970, Moen 1973). The extent to which forage can substitute for milk in meeting energy and nitrogen requirements is dependent upon the development of the gastro-intesti al tract into that characteristic of a ruminant animal which is capable of fermenting large quantities of ingested forage. We gratefully acknowledge funding provided by the New York State Department of Environmental Conservation (PittmanRobertson Project W-124-R). The technical assistance of B. Robbins, T. Supplee, and W. Armstrong is appreciated. 1 Present address: Department of Zoology, Washington State University, Pullman 99163. J. Wildl. Manage. 39(2) :1975 355 This content downloaded from 207.46.13.158 on Wed, 16 Nov 2016 04:27:05 UTC All use subject to http://about.jstor.org/terms 356 WEIGHT GAIN OF DEER Robbins and Moen METHODS AND MATERIALS Twenty-two newborn fawns (14 males and 8 females) were acquired between 26 May and 21 June 1972 from the herd at the BioThermal Laboratory and the New York State Department of Environmental Conservation. The fawns were placed in small wire-covered pens until nursing well, approximately one week. The fawns were randomly divided into two test groups of high (Group I) and low (Group II) milk intake (Fig. 1). Female fawns of each test group received slightly more milk because of the higher fat and caloric content of the gain (Robbins 1973, Robbins et al. 1974). Milk was formulated from evaporated milk, casein, water, and a mineral-vitamin mixture to match as closely as possible the energy and protein composition of whitetailed deer milk (Silver 1961) (Table 1). The milk was warmed to 38 C and given in soft-drink bottles fitted with rubber sheep nipples. Since the casein did not go into solution well, each bottle was rinsed with water from a laboratory wash bottle and the rinse fed to the designated fawn. All fawns were initially fed six times daily at 3.5-h intervals beginning at 0600 until the peak of milk consumption had been reached. The fawns received a different amount of milk each day as determined by their weight in relation to the lactation curves (Fig. 1). The lactation curves were generated prior to the pen experiments from estimates of fawn requirements, efficiencies of nutrient utilization, feed composition, and capability of fawns for substituting dry feed for milk (Robbins 1973, Moen 1973). As the amount of milk fed declined, the number of feedings decreased until the fawns were weaned at 25 kg. Once the fawns were nursing well they were weighed, transferred to three large pens (12.2 x 12.2 m) constructed of slat1000.0