The effect of forage quality and level of feeding on digestibility and gastrointestinal transit time of oat straw and alfalfa given to ponies and donkeys

Four donkeys and four ponies were fed molassed dehydrated alfalfa or oat st raw, either ad libitum or restricted to about 70% ad libitum intake in a La tin-square design for four periods of 21 d. Measurements of apparent digest ibility and gastrointestinal transit time were made on the last 7 d of each period. When the forages were provided ad libitum, all animals ate signifi cantly (P < 0.01) more of the alfalfa than of the oat straw. Ponies consume d significantly (P = 0.007) more of both diets per unit live weight than do nkeys. Higher apparent digestibilities of dietary DM, energy and fibre frac tions were seen in donkeys, at both levels of feeding, compared with the po nies. This partly compensated for the lower intakes by the donkeys when fed ad libitum. When intake of alfalfa was restricted, the apparent digestibil ity of DM was higher compared with the corresponding values when fed ad lib itum, but the reverse was true for straw. This may be because restriction o f a low-quality diet reduced selection of the more digestible parts of the forage. Donkeys and ponies consumed more energy and protein than required w hen fed alfalfa ad libitum. Both oat straw treatments provided insufficient protein to meet the predicted requirements of ponies and donkeys. Straw in takes ad libitum exceeded the estimated energy requirement for ponies by 34 -51%, but donkey energy requirements were only just met. When the amount of straw offered was restricted, 78-90% of the estimated energy requirement f or donkeys was met compared with 90-105% for the ponies.