Nengomasha, Edward Musiwa.

2018-05-22T12:46:14Z

2018-05-22T12:46:14Z

1998

Donkeys are becoming increasingly important for draught animal power (DAP) in Zimbabwe and the sub-Saharan region. This is mainly because catde, the traditional DAP source, have suffered high mortalities in recent droughts. However, there is limited information on the extent of use and potential of donkeys for DAP in Zimbabwe. In an attempt to rectify this deficiency, a rapid rural appraisal (RRA) and a series of studies were undertaken. The RRA was conducted first to assess the status, role and current management practices of DAP in smallholder farming areas in the semi-arid regions of Zimbabwe. Studies were carried out to assess; the morphological characteristics of 335 working donkeys in south-western Zimbabwe, the relations between live weight and body measurements and the seasonal fluctuations of live weight and body condition of selected donkeys in semi-arid areas. The other studies evaluated the draught performance of teams of donkeys and cattle ploughing at different sites. Finally, the effects of drinking water and work on dry matter intake (DMI) as well as apparent dry matter digestibility (DMD) and mean retention time (MRT) of donkeys were investigated.

The results of the RRA showed that large numbers of cattle died (up to 75 per cent in some areas) during the 1991-92 drought and that this had increased the farmers' dependency on donkeys for DAP. However, the management of donkeys was generally inadequate. For example, there was widespread use of the inappropriate neck yokes and improper harnesses on donkeys in some of the areas.

The study on morphological characteristics indicated that the typical "Zimbabwean" donkey weighed 142 ±1.4 kg, had a heart girth of 115 cm (range 93 - ii 140), a height at withers of 105 cm (range 91 - 120) and was normally light grey in colour. Male and female donkeys were of similar weight and body dimensions. The single best predictor of live weight was heart girth (r2 = 0.864) followed by umbilical girth (r2 = 0.753). There were seasonal fluctuations in the live weights and body condition of 38 monitored donkeys with weight losses more apparent late in the dry season (October/November).

When used for ploughing in the wet season, a team of 4 donkeys considered "optimal" for ploughing and 2 oxen of similar total team weights exerted similar draught forces, 867 N and 900 N (P>0.05); generated similar power outputs, 689 W and 920 W (P>0.05); worked at similar speeds, 0.87 m/s and 1.03 m/s (P>0.05) and had similar effective field capacities, 14.2 hours/ha and 14.5 hours/ha (P>0.05), respectively. Lighter donkey teams generated less power output than heavier teams.

Over a 35-day period, individually penned donkeys that had access to water every 48 hours (n = 6) and every 72 hours (n = 6) consumed less water (by 42 per cent, P<0.001), 4.9 ± 0.30 litres/d and 5.1 ± 0.29 litres/d, respectively, compared with 8.5 ± 0.61 litres/d for donkeys with ad libitum access to water (n = 6). This was accompanied by a reduction in DMI of 13 per cent (P<0.05). Donkeys with restricted access to water lost less water through the faeces (by 9 per cent, P<0.05) than those with ad libitum access. Donkey teams subjected to work (carting) had similar DMI to those teams not working. The work did not have an effect on DMI, 3.3 kg DM/d for working and non-working donkeys and neither did the time of access to feed (P>0.05). DMD and the MRT of digesta were not affected (P>0.05) by work.

It was concluded that the shortage of cattle had increased the use of donkeys for DAP in the semi-arid areas of Zimbabwe. Extension information on good management practices and general welfare of draught animals, particularly donkeys, was clearly lacking. The morphological characteristics of male and female donkeys showed few differences and potentially the draught performances of the two sexes could be similar. Donkeys in Zimbabwe were morphologically similar to their counterparts in other parts of Africa implying that these donkey types are related. Heart girth, the best single predictor should be included in predictive equations for estimating live weight using body measurements. Weighbands and nomograms which are important management tools for smallholder farmers should be produced from these predictive equations. Although there were seasonal fluctuations in live weight and body condition of donkeys, these were less than those reported in cattle. Thus, donkeys are more likely to be in better condition at the start of the ploughing season than cattle. Donkey teams were capable of ploughing for up to four hours per day provided they had a sufficient combined team weight to pull the plough. Training and experience are very important factors affecting the performance of working animals. Donkeys were able to continue eating despite the limited access to water and this is an important mechanism for survival during droughts. Working donkeys could not increase DM intake of hay and this was attributed to the poor quality and physical form of the hay. Supplementation of working donkeys might be necessary.

The importance of donkeys is likely to increase in the semi-arid areas where the susceptibility of cattle to the recurrent droughts has been exposed.

http://hdl.handle.net/1842/30568

The University of Edinburgh

Annexe Thesis Digitisation Project 2018 Block 19

Already catalogued

Donkey (Equus asinus) as a draught animal in smallholder farming areas of the semi-arid regions of Zimbabwe

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy