Fine Stemmed Alfalfa Varieties?

We sometimes hear about the use of "fine stemmed" alfalfa varieties to improve forage quality and intake. The term "fine stemmed" is rather subjective and difficult to measure. Provincial and State Forage Variety Trials don't measure the "fine stemmed" trait. Some producers use anecdotal information and their own experience to select "fine stemmed" varieties.

Influenced By Many Factors

"Fine stemmed" is influenced largely by maturity. A few days difference in cutting date can have a big effect. It can also be influenced by plant density (seeding rate), age of stand, stems per square foot (> 40), fertility, disease and insect resistance, etc. There are also some varietal differences. High yielding alfalfa needs to have some degree of structure (stem diameter) to support a greater mass of leaves. And don't forget that excessive leaf loss during cutting, raking and baling can result in "stemmy hay". Stem fineness receives less attention in early-cut haylage programs.

Fibre & Fibre Digestibility

"Fine stemmed" is not the only contributor to forage quality. "Fine stemmed" is an indirect contributing factor in fibre (Neutral Detergent Fibre, NDF) and fibre digestibility (Neutral Detergent Fibre Digestibility, NDFD or Cell Wall Digestibility, CWD). These can be measured in the lab. The same is true for traits that can increase the leaf to stem ratio - multifoliate expression, leaf size, auxiliary stem branching and leaf disease resistance to keep the leaves from falling off. Lignification of the xylem tissue in mature alfalfa stems significantly decreases fibre digestibility.

Cutting Delays

Early-cut alfalfa is finer stemmed and higher forage quality than later-cut alfalfa. But weather and mechanical delays, as well as shear volume can frequently result in some of the crop being harvested with less than optimum quality. Dry hay systems often requires a larger harvest window than haylage. Plant breeders are trying to develop varieties with a slower decrease in forage quality in order to widen the harvest window. Research shows there are typically 8-10 points of genetic difference in Relative Feed Value (RFV) among alfalfa varieties. When put in perspective, cutting delays can result in much larger differences. All varieties will drop to 100 RFV eventually, but some a bit sooner than others.

Seeding some high quality varieties as well as some standard varieties could be used to spread the first-cut harvest window. The standard varieties could be harvested first while the high quality varieties could be cut later.

| Top of Page |

Variety Trials

Lowering NDF and increasing NDFD increases both Digestible Energy and intake, which are very important in high producing dairy cows.

The Ontario Forage Crops Committee led the way in 1991 by evaluating varieties based on NDF and NDFD. It may have been ahead of its time, but was probably underutilized by many dairy producers. Variety forage quality evaluation was discontinued recently because of the cost of obtaining the laboratory data. Data was not available for all varieties, but in the 2002 Forage Variety Performance Brochure, there were 5 or 6 varieties listed that were winners (statistically significant) for both NDF (lower fibre) and NDFD (higher fibre digestibility). Wisconsin has a similar program that uses NDF and NDFD to index alfalfa varieties for quality. Milk Per Ton calculations rank for quality, while Milk Per Acre calculations combine both quality and yield. Most forage seed companies market some alfalfa varieties that they consider their "forage quality" varieties.

Strategy

If high quality, fine stemmed alfalfa is a priority, we can manage for that by earlier cutting. However, at first-cut time the optimum harvest window is often narrow, particularly for dry hay systems. Seeding some high forage quality alfalfa varieties, as well as some standard varieties can be used to help spread the first-cut harvest window.

| Top of Page |