Effect of amount ofPanicum virgatumhay offered on intake, apparent digestibility and short-term intake rate of rams

Abstract

AbstractSwitchgrass (Panicum virgatumcv.Alamo) standing hay was cut and offered to 16 rams. The rams were randomly allocated to one of the following levels of feeding: 0·5; 1·0; 1·5 and 2·0✕maintenance. The forage was offered twice a day to the animals; no supplements were given. The animals were individually penned and fitted with faeces collection bags. After 8 days for adaptation, in vivo dry matter apparent digestibility (DMD) and proportion of blades and stem + sheath of the consumed forage were measured for 8 days. DMD varied from 0·310 (0·5) to 0·391 (2·0) and the proportion of the blade fraction in the diet from 0·44 (0·5) to 0·78 (2·0). The short-term intake rate (STIR) of rams was measured for 5 days. The animals were divided randomly into four blocks, with one ram of each treatment in each block. After 4 h without food and 15 min intervals between blocks, the amount of forage consumed during 4 min of active eating was measured. The amounts consumed were (in g DM per min per 50 kg live weight): 0·5: 8·2; 1·0: 7·8; 1·5: 5·3 and 2·0: 5·3 (0·5 = 1·0 > 1·5 = 2·0;P< 0·01). The results show that offer rate of P. virgatum affects the blade: stem + sheath ratio of intake and, therefore, the nutritive value of the diet. Level of feeding before measuring STIR influences the amount of forage consumed during the test.