UBC Theses and Dissertations
The response of axial growth gradients within the skeleton of the black-tailed deer to variations in the level and pattern of energy availability Addison, Ralor Blendle
A study was designed to examine the interaction of axial growth gradients and time specific energy restrictions upon, the growth rates of skeletal dimensions in the Black-tailed deer. A total of 53 new-born fawns was captured and then reared in captivity on controlled energy regimes. The test period of 322 days was divided into five intervals with the energy level in each interval being set as high, medium, or low plane. Representative animals were killed at the end of each interval to examine growth over the previous intervals and to establish a base for evaluating growth in the next interval. Five wild fawns were collected at 112 days and four at 175 days for comparison with the laboratory standards. Relative growth priorities of 23 skeletal dimensions were investigated by challenging skeletal growth with a series of energy restrictions. The amount of growth exhibited by each skeletal element in response to the level of available energy could be integrated into an interpretation of relative growth priorities. Skeletal growth was examined for its ability to provide an indication of total amount and pattern of energy intake over two intervals at the end of 112 days, over three intervals at the end of 175 days, and over five intervals at the end of 322 days. The degree to which the effects of earlier restrictions were removed by compensatory growth was also examined in the fifth interval. A shortage of animals precluded the sacrifice of any standards at 259 days. When skeletal size was graphed against total energy intake, expressed in Calories of apparent digestible energy, at a fixed age, the pattern of energy intake created a distribution of points which could by conveniently bounded by a triangle. On different patterns of energy intake but equal total energy intakes, the relative sizes of the 23 skeletal dimensions change their positions within the boundaries surrounding the distribution of points. A comparison of a set of measurements from an animal of unknown nutritional history with the reference lines in each of the standard triangular distributions leads to a series of energy intercepts that should uniquely characterize the amount of energy consumed by that animal, and the pattern in which it was available. At 112 days, the total energy intake and pattern of restrictions could be derived from skeletal growth. At 175 days, although estimates of total energy intake still appeared to be good, the pattern of energy intake could not be established exactly, but could be limited to a small number of patterns. By 322 days, compensatory growth had reduced differences in skeletal size to the point where neither amount nor pattern of energy availability could be deduced. Four measurements of the fore cannons from wild fawns at 150 days were used to try to define the nutritional regime with a portion of the skeleton which would be readily available from hunter-killed animals. This did not allow a precise evaluation of the nutritional regime for individual animals, but it did point out that there can be tremendous variability in the energy intake of wild fawns from a relatively small area of habitat. It is suggested that a collection of fore cannons should be made along with that of body weights to allow an improved evaluation of range conditions.
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