Forage Facts

April 2001

Stage of alfalfa maturity at harvest affects forage quality

Harvesting alfalfa at the correct stage of maturity is an important factor in ensuring your highest quality forage. To determine what is the best stage to harvest alfalfa, you first need to define what your forage production goals are.

What is forage going to be used for? (lactating cows, young stock, dry cows, beef cows)

What is your desired RFV range?

How do you intend to harvest the forage? (dry hay, haylage, baleage)

How much of each forage do you need? (bales of hay, tons of haylage, etc.)

Once you have defined your forage production goals, you can use the following information to help you determine the best stage to harvest your forages.

Table 1 gives the feeding value of different types of hay cut at different stages of maturity with good harvest management. As plants grow and mature, the concentration of fiber increases while protein content and digestibility decrease. Hay fed to animals with high nutrient requirements, such as high-producing dairy cows, should be harvested at early growth stages, which are associated with high quality but typically lower yields.

Delaying hay harvest until more advanced stages of growth tends to maximize yields but at considerably lower quality. This is often appropriate when the hay will be fed to animals with lower nutrient requirements, such as gestating beef cows. Grass hays cut at early heading will often meet the cow’s nutrient requirements, but delaying harvest until after pollen shed and seed filling may likely result in hay too low in protein to maintain cows without supplementation. Table 2 gives suggested stages for cutting hays to obtain high quality hay or maximum hay yield.

 

Crop	Stage for High Quality Hay	Stage for Maximum Yield
Alfalfa	First cutting – late bud Other cuttings – early bloom	Mid – bloom
Brome or Crested	Boot stage	Flowering
Cereal Grains	Boot stage	Soft dough
Prairie Grass	Boot stage	Late head

Information condensed from NEB GUIDES G84-738-A and G88-874-A; University of Nebraska.

By Mike Rankin, Univ of Wisconsin, Crops & Soil Agent, Fond du Lac County

Step 1: Choose a representative one square foot area in the field.

Step 2: Determine the stage of the most mature stem in the area using the following criteria:

Late vegetative: Stem over 12 inches tall with no visible buds or flowers

Step 3: Measure the height of the tallest stem in the one square foot area from the soil surface (crown base) to the top tip of the stem (not the tip of the leaf.)

Step 4: Based on the most mature and tallest stem, use the chart on the next page to estimate relative feed value.

Step 5: Repeat the above procedure in 5 to 10 areas of the field to obtain a whole field RFV average.

Note: This procedure estimates the forage quality of the standing crop and does not account for changes in quality due to wilting, harvesting, and storing. These factors may further lower RFV 20 to 30 points. Variations may also exist among alfalfa varieties. For dairy quality forages, cut alfalfa when standing crop estimates reach RFV 170.

Example: In a one square foot area, the most mature stem has three nodes with visible buds but no open flowers (late bud.) The tallest stem measures 31 inches from the soil surface. The estimated RFV is 153.

Table 3. Predicting first-cut alfalfa relative feed value.

Height of Tallest Stem	Late Vegetative	Early Bud	Late Bud	Early Flower	Late Flower
Inches
16	234	220	208	196	186
17	229	215	203	192	182
18	223	211	199	188	178
19	218	206	195	184	175
20	213	201	191	181	171
21	209	197	187	177	168
22	204	193	183	173	166
23	200	189	179	170	161
24	195	185	175	167	158
25	191	181	172	163	155
26	187	178	169	160	152
27	184	174	165	157	150
28	180	171	162	154	147
29	176	167	159	151	144
30	173	164	158	148	141
31	169	161	153	146	139
32	166	158	150	143	135
33	163	155	147	140	134
34	160	152	145	138	132
35	156	149	142	135	129
36	154	148	139	133	127
37	151	144	137	131	125
38	148	141	134	126	123
39	145	139	132	125	121
40	142	138	130	124	118
41	140	133	127	122	118
42	137	131	125	120	114
43	135	129	123	118	113
44	132	126	121	116	111