Some factors affecting the digestible energy requirements and dry matter intake of mature donkeys and a comparison with normal husbandry practices
Wood, Stephanie Jane
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The purpose of this study was to compile practical feeding guidelines for donkeys in the UK. Current guidelines are to feed 0.75 of horse feeding recommendations on a body weight basis. However, the superior digestive efficiency of donkeys, compared to horses, may render the use of horse recommendations inappropriate. The formulation of guidelines specific to donkeys would enable owners to calculate their donkey‟s requirements with greater accuracy and prevent overfeeding. A postal survey, used to gain information on the body condition score of donkeys in the UK, and the husbandry and feeding practices used to manage them, indicated that approximately 24% of donkeys in the UK are overweight. Feeding practices indicated that although owners were aware of their donkey‟s requirement for fibrous forages, the practice of feeding unnecessary concentrates, chaffs and high energy forages, in addition to grazing, was the likely cause of donkeys becoming overweight. The finding that the majority (85 – 90%) of donkeys were kept as non-working companion animals also reduced the need for owners to feed higher energy foods to their donkeys. Results also suggested that owners were unsure of how to adjust their donkey‟s diet to account for seasonal changes in requirements and pasture availability, as most owners‟ adjusted grazing access, and not the feeding of supplementary feeds. From a study of dry matter (DM) and digestible energy (DE) intakes by 20 mature donkeys maintaining weight during each UK season, the maintenance DE requirements of donkeys were calculated. Results showed no effect of sex on DM or DE intake. Season significantly (P<0.001) affected DM and DE intakes, implying increased requirements in winter compared to spring, summer and autumn. Dry matter intakes (DMI) increased from 51g/kg BW0.75 in spring, summer and autumn to 66g/kg BW0.75 in winter. Digestible energy requirements increased from 0.32MJ/kg BW0.75 in spring, summer and autumn to 0.43MJ/kg BW0.75 in winter. Comparison of results with horse recommendations showed considerably reduced requirements by donkeys. Horse recommendations overestimated DE requirements in summer and winter by 82 and 30%, respectively, making horse recommendations unsuitable for calculating donkey energy requirements. Husbandry practices commonly used by owners to manage their donkeys grazing access (grazing time, grazing area, strip grazing), were assessed for their effect on DMI by grazing donkeys in summer and autumn, using n-alkanes. The effect of grazing time was assessed by restricting donkeys to 8, 12 or 23 hours grazing per day. Season significantly affected food intake with donkeys in the 8 and 23 hour grazing groups eating more during summer when pasture availability was greater. Donkeys responded to the poorer quality summer pasture by grazing more intensively but less selectively, increasing the rate at which food was consumed. Grazing time was only influential over grass intake in summer, when pasture was more abundant. Restricting donkeys to 12 hours or less grazing per day significantly (P<0.001) reduced their grass intake compared to that of donkeys with 23 hours access. When grazing sparse pastures (autumn), grazing time did not influence grass intake, indicating an effect of herbage mass on grazing behaviour. Herbage mass was the most influential factor over diet composition (percentage of grass and straw consumed) in a second grazing study assessing the affect of strip grazing and set stocking systems on intake by grazing donkeys during summer and autumn. Herbage mass per donkey was higher in the set stocking system during both seasons, resulting in higher grass intakes. Determining if either grazing system was more effective at regulating grass intake was prevented due to differences in pasture availability between study sites. It is concluded that donkeys have lower DMI and maintenance DE requirements than horses, requiring donkey feeding guidelines to be formulated. Excess body weight in donkeys is caused in part, by the feeding of energy dense feeds in addition to low energy forages. Most owners place little nutritional importance on pasture, despite its potential to provide a large percentage of daily DM, DE and nutrient intake. Therefore nutritional guidelines must include advice on how to manage access to grazing, and how to feed donkeys with access to pasture. Restricting grazing time to 8 hours a day did reduce grass intake by donkeys, but was only effective when grazing abundant pastures. Providing ad libitum straw to grazing donkeys allows them to satisfy their DM and dietary fibre requirements without consuming excess energy.