A note on the influence of negative gradients on the energy expenditure of donkeys walking, carrying and pulling loads

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Abstract
The extra energy used for walking on the level and on negative gradients above that used when standing still (Ew) (J/m per kg live weight) was measured in two entire male donkeys (Equus asinus). Ewwas not affected by speed within the measured range (V = 0·6 to 1·3 m/s) but gradient (0, −10%, −15%) had a significant effect Ew−10%= 0·97 (s.e. 0·02), Ew−10%= 0·55 (s.e. = 0·03) and Ew−15%= 0·67 (s.e. 0·03).The extra energy cost of carrying loads (Ec), defined as J/m per kg carried was measured using the same animals. Loads were placed over the animals shoulders and speed was varied within the range 0·6 to 1·3 m/s (Eclevel= 1·1 (s.e. 0·04), Ec−10%= 2·7 (s.e. 0·17) and Ec−15%= 3·3 (s.e. 0·20) were significantly different.The energy cost of pulling loads (Ep) (f/m per kg) was measured while the animals pulled loads up to proportionately 0·17 of their live weight. The animals wore a breast-plate harness and walking speed was varied within the range 0·6 to 1·3 m/s. Mean values were 26·5 (s.e. 0·72) on the level, 15-3 (s.e. 1·2) on the −10% gradient and 6·2 (s.e. 0·43) on the −15% gradient.The two donkeys used in this experiment were more efficient in both carrying and pulling loads than oxen and buffaloes. Negative gradients have a significant effect on energy consumption and when estimating the energy expenditure of working animals this factor should be taken into account.