Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/28/2000
Publication Date: N/A
Citation: Interpretive Summary: Alfalfa hay production in the United States has been stable the last 5 years. However, alfalfa hay production is shifting from the Midwest to Western states. Western alfalfa hay producers sell to livestock producers rather than raising alfalfa for livestock production on the same farm, a common Midwestern practice. Western alfalfa hay is being harvested in mid-size rectangular bales, 880-pound weights. Research information is needed to determine if the same number of cores taken from Midwestern small rectangular bales is needed to obtain desired accuracy when sampling larger bales. This evaluation of 3 commercial hay lots showed that sampling 12 different bales once from within the hay lot accurately represents the protein, dry matter and fiber concentrations of a 880-pound, mid-size rectangular alfalfa hay lot. This research is different from findings using small 45- to 90-pound rectangular bales. Accuracy of forage analysis sof small bales requires cores taken from each of 20 bales. This research will be of benefit to one-third of U.S. alfalfa producers who use mid-size bales. The producers will save time collecting hay samples that represent a hay lot or load for an analysis of forage quality.
Technical Abstract: Commercial lots of alfalfa (Medicago sativa L.) hay are often bought and sold on the basis of forage quality. Proper sampling is essential to obtain accurate forage quality results for pricing of alfalfa hay, but information about sampling is limited to small, 20- to 40-kg rectangular bales. Our objectives were to determine the within-bale variation in 400-kg rectangular bales and to determine the number and distribution of core samples required to represent the crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and dry matter (DM) concentration in commercial lots of alfalfa hay. Four bales were selected from each of three hay lots and core-sampled nine times per side for a total of 54 cores per bale. There was no consistent pattern of forage quality variation within bales. Averaged across lots, any portion of a bale was highly correlated with bale grand means for CP, ADF, NDF, and DM. Three lots of hay were probed six times per bale, one core per bale side from 55, 14, and 14 bales per lot. For determination of CP, ADF, NDF, and DM concentration, total core numbers required to achieve an acceptable standard error (SE) were minimized by sampling once per bale. Bootstrap analysis of data from the most variable hay lot suggested that forage quality of any lot of 400-kg alfalfa hay bales should be adequately represented by 12 bales sampled once per bale.