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Energy and protein requirements of fallow deer under a Mediterranean environment by Y. J. Ru and P. C. Glatz
April 2004
RIRDC Publication No 02/110 RIRDC Project No SAR-21A
Red weaner deer, fallow weaner deer and Merino sheep were housed in an animal house to compare the digestibility of 12 diets. The outcomes of this study showed no differences between sheep, red and fallow deer in digestibility of dry matter, organic matter and digestible energy content for all diets except for sorghum and medic hay. An in vitro study demonstrated that the Tilley-Terry method and near infrared spectroscopy (NIR) have potential as a rapid feed evaluation system for deer, but need further validation. The data on chemical composition and nutritive value of these feed ingredients can be used by nutritionists and deer farmers to formulate the supplementary diets based on the availability and price of these feed resources.
Quantifying the amount of nutrients deer can obtain from grazing pastures is essential so that deer farmers can determine the amount and the time that supplementary feeding is required during the season. Many methods can be used to estimate forage intake, including exclusion cages, chromium oxidate (Cr2O3) and differences pre and post grazing, but these methods can only be used to estimate the average intake. However, the recently developed method-the alkane technique, is used in sheep for estimating feed intake of individual animals and their diet composition. To assess the potential of using alkanes as a marker for predicting feed intake of fallow deer, the daily faecal recovery of alkanes and excretion rate of dosed artificial alkanes were measured. It was found that the while faecal recovery of natural alkanes is incomplete, the faecal concentrations of alkanes can be adjusted to provide an accurate estimation of intake. The outcomes of this experiment clearly show that the alkane technique can be used to measure feed intake under grazing conditions.
While the alkanes in plant materials can potentially be used as makers to estimate composition and digestibility of the diet of deer, the analysis of alkanes in plant materials and deer faeces is time consuming and expensive. In this study, the potential of using NIR to predict alkane content in faecal and pasture samples was assessed. NIR can be used to predict the content of most alkanes except for alkanes with chains of C24, C26, C32 and C36 in faecal samples and C24, C25, C26 and C36 in pasture samples. The use of these NIR calibrations will accelerate the estimation of diet digestibility, dietary components and botanical composition of pastures.
The determination of nutrient requirements of grazing fallow deer consisted of the measurement of forage intake of individual deer and the establishment of relationship between body weight gain and daily nutrient intake. The relationships between body weight gain and intake of metabolisable energy and crude protein were established using a general linear model. The crude protein, DE and DM intake from pastures increased from May to October and was influenced by the level of supplementation during early winter. The group with a lower supplementation had a higher forage intake. Female deer ingested less pastures than male deer, especially after August. There was a strong correlation between intake and sward height (cm). The digestible energy and crude protein requirements were strongly correlated with body weight gain. These data can be used to assist farmers to develop pasture and stock management practices under southern Australian conditions.
In practice, deer farmers need advice on the amount of supplementary feed and what type of feed should be offered to deer. An experiment was carried out to determine the feeding levels of fallow weaner deer from May to July, where nutrient supply from pasture was limiting. The results showed that the body weight was similar for low, medium and high feeding levels in April and May, although deer fed low levels had a lower live weight during July-October. Female deer grew slower than male deer, especially in September and October. Yearly variations in growth resulted from the different types of pastures used, indicating it is crucial for nutrient intake from pastures to be determined for developing supplementation strategies.
Three diets were formulated based on oats, oats-lupin and triticale. Supplementary diets were offered ad libitum from April to July. The predicted digestible energy and protein content were 13.5 MJ/kg, 10.8% for diet 1, 13.2 MJ/kg, 15.9% for diet 2, 13.5 MJ/kg and 10% for diet 3. The actual supplementary feed intake were 328, 423, 548 and 567 g/day in April, May, June and July, respectively. The feed intake was low, especially in April and May although feed was offered ad libitum, which was consistent with the previous observations. No difference in body weight was found during the season between the diets, but male deer grew faster than females, especially from August to October. The increase in protein level by including lupins in the diet based on oats did not improve the growth rate of weaner deer. Based on the cost and the final body weight in October, it is obvious that oats and triticale is more cost-effective than barley/lupin. The increase in energy concentration in the supplementary diet for the April/May period can be achieved by adding oil or tallow and will improve the growth performance of weaner.
The data obtained during this project can be immediately adopted by deer farmers to develop supplementary feeding and pasture management strategies during the season and will ensure quality venison is produced cost-effectively.
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