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Title: The impact of grazing time allowance on the dry matter intake and foraging behaviour of cattle and donkeys managed under traditional African grazing systems
Author: Smith, David G.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1999
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Restricted nutrient intake is the largest, single factor that limits the productivity of grazing animals. Traditional African grazing systems (TAGS) appear to exasperate this constraint by restricting the amount of time available to feed. This project set out to investigate the effect of TAGS on the forage intake of free-ranging cattle and donkeys in order that recommendations for their improved nutrition and productivity could be formulated and disseminated to resource-poor livestock owners in Africa. The thesis is sub-divided into two sections, the first section reports the modification of techniques used to carry out the study and the second the results of animal studies carried out in Scotland, Ethiopia, and Zimbabwe. Modifications of techniques for the estimation of DMI using the ratio technique included: 1) development of a method for the rigid simultaneous dosing of even-chain alkane and chromic oxide external markers in order to reduced circadian variation of faecal marker output; 2) the identification of acid-detergent lignin (ADL) as the most reliable internal marker for the estimation of dry matter digestibility (DMD); 3) the development of an in vitro DMD technique that improved correlation (r2 = 0.96) with in vivo DMD measured in equids compared to the non-modified method (r2 = 0.85); 4) a hand-plucking method for obtaining a representative sample of forage ingested by free-range cattle and donkeys. Restricting the grazing time of cattle to only eight hours per day had no effect on their DMI in both Ethiopia and Zimbabwe. Cattle compensate for RFT by increasing ETPH and by increasing bite rate. Traditional grazing management in African communal systems does not therefore appear to significantly limit nutrient intake by cattle. The effect of TAGS on the nutrient intake by donkeys is much greater than in cattle; restricting the time available for eating limits DMI and reduces the quality of ingested forage because the animals are less selective. Donkeys must therefore be managed separately from cattle and this is particularly important, when they are used for work. Donkeys are much less able to compensate for loss of eating time due to work than are cattle, because they have evolved to spend much longer eating.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available