Hay and forage discussions come with a specialized vocabulary that can be confusing for small-farm owners new to hay purchasing and management. This glossary defines the most commonly encountered terms in plain language.

A

ADF (Acid Detergent Fiber)
A measure of the least digestible components of hay — primarily cellulose and lignin. Lower ADF means more digestible hay. ADF is used to calculate energy content (TDN) in forage analysis. See Reading a Hay Quality Test.
Alfalfa
A legume hay crop with high protein (18–22% CP) and calcium content. Best for high-production animals; inappropriate as primary hay for easy-keeper horses, wethers, and bucks. See Hay Types Explained.
As-Fed Basis
Nutritional values reported including the water content of the hay. Compare samples on a dry matter basis for fair comparison. See forage analysis guide.

B

Baling
The mechanical process of compressing cut and dried hay into bales for storage and handling. Round balers produce cylindrical bales; square balers produce rectangular bales of various sizes.
Boot Stage
The growth stage of grass when the seed head is fully formed inside the uppermost leaf sheath but has not yet emerged. Hay cut at boot stage is typically higher in quality (protein, digestibility) than hay cut after seed head emergence.
Browse
Woody plants, shrubs, and tree leaves consumed by ruminants, particularly goats and deer. Not a substitute for hay but a natural dietary supplement.

C

CP (Crude Protein)
Measured as percent nitrogen × 6.25. The standard measure of protein content in forage analysis. Higher CP supports growth, reproduction, and milk production. See the forage analysis guide.
Curing
The field-drying process between mowing and baling. Adequate curing (typically 2–4 days in good drying weather) reduces moisture to safe baling levels (below 18–20%). Inadequate curing leads to mold and heat damage.
Cutting
Sequential harvest of hay field regrowth. First cutting is the first harvest of the season; second and subsequent cuttings are from regrowth. Each successive cutting is typically leafier and higher in protein. See First vs Second Cutting.

D

Dry Matter (DM)
The portion of hay that is not water. Nutritional values expressed on a dry matter basis remove moisture variability, allowing fair comparison between samples with different moisture contents.
Dry Matter Loss
The percentage of hay's nutritional value lost to weather exposure, mold, or animal waste during storage. Ranges from 2–5% (inside barn) to 25–40% (uncovered on bare ground). See Preventing Dry Matter Loss.

E–F

Endophyte
A fungus that lives within tall fescue grass plants. Toxic endophyte strains produce ergot alkaloids that cause fescue toxicosis in livestock, particularly in horses and breeding cattle. See Hay Types — Fescue section.
Flushing
The practice of increasing energy intake in ewes or does 2–3 weeks before breeding to stimulate higher ovulation rates and improve twinning percentages. Done with better-quality hay or grain supplementation.
Forage Analysis / Hay Test
Laboratory testing of hay to determine nutritional content — CP, ADF, NDF, TDN, RFV, and mineral levels. The only reliable way to know the actual nutritional value of a hay batch. See Reading a Hay Quality Test.

H–L

Haylage
Fermented hay preserved in an anaerobic environment (plastic wrap or sealed storage) at higher moisture than dry hay (40–60% moisture). Requires sealed storage and must be fed within days of opening. Different feeding management than dry hay.
Legume
Hay crops in the legume family — alfalfa, clover, lespedeza. Higher in protein and calcium than grass hays. Fix nitrogen from the atmosphere, reducing fertilizer requirements on legume fields.
Long-Stem Forage
Hay in its natural baled form, with intact stems and structure. Distinguished from hay cubes, pellets, or chop, which are processed forms. Long-stem forage is essential for dental wear in horses and rabbits, and for normal rumen function.

M–N

Mycotoxin
Toxic compounds produced by mold fungi in hay and grain. Can cause colic, respiratory disease, reproductive problems, and liver damage depending on the toxin and exposure level. Horses are particularly sensitive.
NDF (Neutral Detergent Fiber)
Total cell wall fiber content of hay. Higher NDF = more physically filling but lower nutrient density per pound. Higher NDF limits voluntary intake — important for high-production dairy animals that need to consume large quantities. See forage analysis guide.
Net Wrap
Plastic mesh wrapped around the outside of a round bale by the baler. Net-wrapped bales hold shape better than twine-tied bales, shed rain more effectively, and have lower outdoor storage dry matter losses. Preferred for outdoor storage.

R–T

RFV (Relative Feed Value)
A composite index combining digestibility (ADF) and intake potential (NDF) into a single quality score. RFV 100 is the NFTA standard reference (full-bloom alfalfa). Higher RFV = better overall feeding value. See forage analysis guide.
TDN (Total Digestible Nutrients)
A composite energy measure calculated primarily from ADF. Expressed as a percentage of dry matter. Higher TDN = more energy per pound of hay consumed. Typical grass hay: 52–58% TDN. Premium alfalfa: 62–68% TDN.
Tedding
Machine operation that fluffs and turns cut hay in the field to speed drying. Tedded hay cures faster, reducing rain-damage risk during the field-drying period.

Reference Pages