Comparison of collection methods for determination of forage nutritive status

Forage samples were collected from pastures amended with one of five biosol ids (municipal sludges) and fertilizer treatments (year one) or eleven trea tments in year two. Forage samples were collected six times during each yea r, once every 28 d, beginning in mid-June. Two methods of forage collection were compared, the cage method and the transect method. The transect metho d involved collecting samples at different areas of a pasture to more close ly mimic what the animals appeared to consume. In year one, forage samples obtained using the cage method were collected from permanent cages (approxi mately 2 m diameter) randomly placed, but then fixed in position in each pa sture. In year two, the cages were randomly moved to new spots following ea ch sampling and mowing. During year one, copper (Cu), zinc (Zn), and iron ( Fe) concentrations differed (P<0.05) by collection method several times, wi th microelement concentrations from cage samples routinely being higher tha n from transect samples. Differences were observed at fewer sampling times during year two for Cu and Fe, but Zn concentrations differed at each sampl ing time. The macroelements followed a similar pattern, with more differenc es due to collection method observed during year one than year two. The in vitro organic matter digestibility (IVOMD) and crude protein (CP) results s uggest an effect of increasing maturity for the transect samples contributi ng to the differences observed in collection methods in year one. When fora ge collection methods differed in forage mineral concentrations, cage sampl es gave routinely higher units but this difference was reduced when cages w ere moved to new locations following sampling.