Time for First Cutting

It is time or almost time for the first cutting of forages, depending on your location in Ohio and your forage quality goals. Orchardgrass was shooting a head in central Ohio last week. The alfalfa stands that were not severely injured by winter are looking great and about ready for first cutting as well across central Ohio. So begin to look for that open weather window for putting up some good forage.

For high quality feed, such as for lactating dairy cows, pure grass stands should be harvested in the late boot stage just before the heads start to peek out. The neutral detergent fiber (NDF) content of pure alfalfa stands can be estimated with the method described in an accompanying article.

A timely first and second cutting is critical for high quality forage. Fiber accumulates faster in the first two growth cycles in May and June than it does later in the summer. So for high quality forage, take your first and second harvest early if at all possible. Later in the summer (July into August) you can extend the cutting interval because the quality decline with delayed cutting is much less then than it is this time of the year.

An exception to the above rule of timely first cutting is for forage stands that suffered significant injury this past winter. Winter injured stands should be allowed to recover longer this spring and get into the bloom stage to build up energy reserves. This will help plants to recover from winter injury and regrow the rest of the summer. Use that forage for animals having lower nutrient requirements.

If high quality isn’t such a concern, we still have a little time before first harvest. For beef cows or other animals with lower nutrient requirements, you can harvest forage in the bloom stage for adequate quality, and it will provide higher yields. But don’t get too comfortable waiting. Keep an eye on the forage because it changes fast this time of year.

Here are the NDF targets (dry matter basis) to shoot for depending on class of livestock:

Forage NDF for Lactating Dairy Cows
Legumes: 35 to 42%
Grasses: 50 to 53%
Mostly legume: 42 to 45%
Mix: 44 to 48%
Mostly grass: 46 to 49%

Estimating Pre-Harvest Alfalfa NDF in the Field

Alfalfa neutral detergent fiber (NDF) concentration can be estimated in the field before harvest by following a simple procedure while walking across the field:

1. Choose a representative 2-square foot area in the field.
2. Determine the most mature stem in the sample area:
   
   • Vegetative = no buds or flowers are visible;
   • Bud = 1 or 2 nodes with buds visible;
   • Flower = 1 or more nodes with open flowers.
3. Measure the length of the tallest stem in the sample area. Measure it from the soil surface to the tip of the stem (not the leaf tip, but the stem tip). Straighten the stem to its full length when measuring. The tallest stem may not be the most mature stem you find.
4. Based on the stage of the most mature stem and length of the tallest stem, read the estimated NDF from the table below. For example, if the most mature stem has buds but no flowers and the tallest stem is 28 inches, then NDF = 38.0.
5. Repeat steps 1 to 4 in several representative areas of the field and calculate the average value. More estimates gives a better overall average.

Note: This estimates the NDF of the standing crop and does not account for changes in fiber due to wilting, harvesting, and storage, all of which can raise the NDF by 3 to 6 units, assuming good wilting and harvesting conditions.

Estimated Pre-Harvest Alfalfa NDF

Length of tallest stem	Vegetative	Bud Stage	Flower Stage
(inches)	% NDF	% NDF	% NDF
16	28.5	29.7	31.4
17	29.2	30.4	32.0
18	29.9	31.1	32.7
19	30.6	31.8	33.4
20	31.3	32.5	34.1
21	32.0	33.2	34.8
22	32.7	33.9	35.5
23	33.4	34.6	36.2
24	34.0	35.3	36.9
25	34.7	35.9	37.6
26	35.4	36.6	38.3
27	36.1	37.3	38.9
28	36.8	38.0	39.6
29	37.5	38.7	40.3
30	38.2	39.4	41.0
31	38.9	40.1	41.7
32	39.6	40.8	42.4
33	40.3	41.5	43.1
34	40.9	42.2	43.8
35	41.6	42.8	44.5
36	42.3	43.5	45.2
37	43.0	44.2	45.8
38	43.7	44.9	46.5
39	44.4	45.6	47.2
40	45.1	46.3	47.9