Grazing methods and stocking rates for direct-seeded alfalfa pastures: II. Pasture quality and diet selection.
A 2-yr study was conducted to determine the effects of two grazing methods (GM) and two stocking rates (SR) on alfalfa (Medicago sativa L. var. WL225) pasture quality and diet selection by Holstein steers. Eight pasture plots (.76 ha) were seeded in 1988 and divided into two blocks of four pastures each. Pastures were managed to allow a 36-d rest period with an average grazing season of 105 d. Before steers entered the next paddock, canopy heights (CH) of alfalfa plants were determined and pasture-forage samples were collected. Forage samples were analyzed for DM, OM, CP, and in vitro OM digestibility (IVOMD). At 12-d intervals beginning with the second grazing cycle, extrusa samples were collected from steers with esophageal fistulas. Extrusa samples were frozen, freeze-dried, and analyzed for OM, CP, IVOMD, in situ ruminal DM degradation, and ruminal undegradable protein. There were no effects of GM on alfalfa CH or pasture DM, OM, CP, and IVOMD. Increasing the SR increased pasture CP content in both years and increased DM, OM, and IVOMD in the 2nd yr. There was no effect of GM or SR on the quality of forage selected by esophageally fistulated steers. Esophageally fistulated steers selected forage that had greater OM, CP, and IVOMD than the average nutrient content of the forage. Although forage quality was greater when stocking rates were increased, the quantity of forage available per animal may have limited gains.
Schlegel
M L
ML
Department of Animal Science, Michigan State University, East Lansing 48824-1225, USA.
Wachenheim
C J
CJ
Benson
M E
ME
Ames
N K
NK
Rust
S R
SR
D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002417:Cattle / Q000254:growth & development*; D004063:Digestion; D004947:Esophagus; D000455:Medicago sativa / Q000254:growth & development / Q000592:standards; D009753:Nutritive Value