Reduced-lignin alfalfa – Dr. Daniel Undersander, University of Wisconsin-Extension
Lignin is the key plant cell wall component that gives a plant strength to stand up and prevent water from leaking during transport from the root to the leaves. This may be good for the plant, but lignin also reduces plant cell wall digestibility in mammals. For these reasons, we want to find the proper balance of lignin to support the plant without drastically reducing digestibility.
Alfalfa normally contains 6 to 8 percent lignin, but more recent alfalfa varieties have been bred to produce 12- to 15-percent less lignin. While the information within this article can be applied to all reduced-lignin alfalfa varieties, the greatest impacts will be seen in the varieties with the greatest reductions.
When choosing a reduced-lignin variety, farmers can choose from the following advantages:
1. Higher quality forage if harvesting at the same time as in the past.
2. Greater yield if harvest is delayed to reach the same quality as in the past.
3. Greater flexibility to choose either of the previous benefits – but not both – depending on the weather.
Producers with very high levels of milk production will likely choose higher forage quality. They will benefit from the greater energy content, but mostly from increased dry matter intake (DMI) where a 10-percent increase in neutral detergent fiber digestibility (NDFd) would equal an increase in 2.2 pounds of milk per day. However, this milk increase would only be expected if alfalfa is cut on a normal schedule, cow DMI increases, body condition score (BCS) is good and cows are in early lactation. Note, if forage quality increases, manure quantity will decrease.
The greatest benefit to many producers will be the increase in yield from a five- to seven-day harvest delay to achieve the same forage quality as in the past. Our data shows alfalfa dry matter (DM) increases by an average of 160 pounds per acre per day around harvest. This means delaying harvest will result in 800 to 1100 pounds more yield per cutting while achieving the same forage quality as in the past. This can particularly benefit farmers cutting on a 28-day schedule that have unused growing season left at the end of the summer. For example, if they take fourth cutting on August 20, they could wait until early September to take the last cutting.
The delayed harvest could also increase plant health, resulting in improved persistence and earlier spring green-up.
Farmers who plant grass with alfalfa can also benefit from reduced-lignin varieties. The biggest concern for farmers is first cutting when grass species produce stems and often mature sooner than alfalfa. This forces producers to time harvest around the grass rather than alfalfa maturation. However, if harvest is delayed, the final forage quality will benefit from the higher fiber digestibility of reduced-lignin alfalfa. Additionally, grasses tend to stay vegetative on later cuttings, so the maturity of the alfalfa would determine the cutting timeline and reduced-lignin alfalfa would have a wider harvest window.
Overall, reduced-lignin technology will give livestock producers more options to maintain forage quality in the field while improving digestion of the plant cell wall components. It is ultimately up to livestock managers to determine if the technology is of value to their operations.