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The estimation of food intake, and its seasonal variation, in the Hartebeest
Author(s) -
PRICE M. R. STANLEY
Publication year - 1977
Publication title -
african journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.499
H-Index - 54
eISSN - 1365-2028
pISSN - 0141-6707
DOI - 10.1111/j.1365-2028.1977.tb00385.x
Subject(s) - specific gravity , biology , zoology , forage , rumen , dry season , ecology , food science , chemistry , mineralogy , fermentation
Summary This paper describes a method of estimating the food intake of a grazing species, Coke's hartebeest, using material from thirty‐two freshly killed animals, taken in different seasons. The literature suggests that the retention time of particles in the cow's rumen is dependent on their specific gravity. The proportions of the leaf, sheath and stem of grasses in the hartebeest's rumen were assessed and their specific gravities measured. Their characteristic retention times, used in conjunction with the weight of rumen contents, allowed calculation of the daily intake of each hartebeest. The use of specific gravity is justified by the relationships between the specific gravity and proximate composition of the grass samples. The intakes showed a three fold range, with the lowest mean value of 26.1 ±4.7 g/kg.W* 73 . day in the dry season. A reduced intake of low quality feeds is consistent with published theories on the factors regulating the intakes of roughages by ruminants. The hartebeest's changing intake is paralleled by other changes in its digestive tract, notably the concentrations of nitrogen in the rumen and faeces. A regression predicting the hartebeest's intake from the faecal nitrogen concentration is developed. Intake is shown to depend upon the water content of the diet, through its effect on specific gravity and hence retention time. The water content is determined by the effective rainfall over the previous 3 months. The limitations of the method, particularly in the measurement of specific gravity, are discussed. A number of reported intakes by cattle and sheep, with the result of a feeding trial with one hartebeest, are presented to show that the estimated intakes may be close to their actual values.