Nutritive quality and palatability of switchgrass hays for sheep: effects of cultivar, nitrogen fertilization, and time of adaptation.
Feeding and palatability trials were conducted with four cultivars (cv) of switchgrass (Panicum virgatum L.), fertilized at three levels of N (0, 75, or 150 kg of N/ha) in 2 yr. Wether sheep had ad libitum access to chopped hays, and intake, apparent digestibility, particle passage rates, and concentrations of blood metabolites were determined. Palatability was measured with mature sheep in cafeteria trials. Nitrogen fertilization did not affect (P > .05) DM digestibility (DMD) or DMI, but there was a year x N interaction (P < .01) for NDF digestibility. Dry matter digestibility values for combined years and N levels were 56.9, 54.4, 56.6, and 57.9% (P < .01) for Pathfinder, New Jersey 50, Kentucky 1625, and Trailblazer cv, respectively; mean DMI values were 60.4, 60.8, 57.7, and 64.0 g/kg BW.75 (year x cv, P < .01). An apparently greater quality of Trailblazer was masked by weed invasion of N-fertilized stands of this cv in yr 2, with changes in hay composition. Lambs adapted to hay diets with time; mean DMI for cv and N levels combined increased (P < .001) from 50.5 to 71.4 g/kg BW.75 between wk 2 and 3 and wk 10 and 11, with no change in DMD. Intakes of NDF increased from 37.6 to 55.6 g/kg BW.75, an increase of 48%. Marker (Yb) measurements indicated little change in particle passage rates with treatment. There were no major differences in blood composition, apart from increases in blood urea N, as a result of N fertilization. Cafeteria trials showed preference by sheep for Trailblazer and KY 1625 compared with NJ 50 and Pathfinder, with a N x cv interaction (P < .01). Trailblazer was preferred to KY 1625 in a two-choice situation (P < .01). Results show relatively small effects of cv and N fertilization on quality of switchgrass and indicate the need for a lengthy period of adaptation by sheep to the feeding of a warm-season grass.
Reid
R L
RL
Division of Animal and Veterinary Sciences, West Virginia University, Morgantown 26506-6108.
Jung
G A
GA
Puoli
J R
JR
Cox-Ganser
J M
JM
Scott
L L
LL
D000821:Animal Feed / Q000032:analysis / Q000592:standards; D000818:Animals; D001806:Blood Urea Nitrogen; D004043:Dietary Fiber / Q000032:analysis; D004063:Digestion; D004435:Eating; D005308:Fertilizers; D005772:Gastrointestinal Transit; D008297:Male; D009584:Nitrogen; D009752:Nutritional Status; D009753:Nutritive Value; D006109:Poaceae / Q000737:chemistry; D012756:Sheep / Q000097:blood / Q000502:physiology*; D013649:Taste
D004043:Dietary Fiber; D005308:Fertilizers; D009584:Nitrogen