The William H. Miner

Agricultural Research Institute

Miner Institute
Farm Report

FROM THE PRESIDENT'S DESK – BURNISHING THE FORAGE CROWNS

It’s often said that alfalfa is the “queen” and corn silage the “king” of forages, based on their widespread use and importance in dairy rations. A crowning achievement of both crops is the highly digestible fiber they both bring to the diet. Recent research burnishes their crowns with exciting new advances that enhance their fiber digestibility and nutritional quality.

California researchers reported that transgenic alfalfa lines with down-regulated lignin synthesis have up to 16% greater in-vitro dry matter digestibility than control lines. These alfalfa lines are genetically modified for lower activity of key enzymes in the lignin synthesis pathway. As an additional benefit, these researchers assessed whether adding tannic acid to the in-vitro systems would improve protein use. Tannins slow rumen protein digestion in many plants, resulting in greater rumen-escape protein and more protein digestion in the lower gut, but alfalfa does not contain tannins. Tannic acid addition to the in-vitro systems increased gas production (i.e. digestibility) of these low-lignin lines. These results need to be proven with animal feeding studies and the low-lignin alfalfa lines must have acceptable agronomic characteristics such as yield and stand persistence. But, as the authors point out, the potential to combine lignin down-regulation with genetic modifications for expression of tannin genes in alfalfa could result in alfalfa of the future with greater fiber digestibility and enhanced nitrogen efficiency when fed to dairy cattle. That would be an excellent combination if you’re feeding dairy cattle. Stay tuned.

Last November in the Farm Report, I discussed a new genetic mutation in corn that results in lower content of ferulate esters and ether cross links at typical silage maturity stages (abbreviated as sfe). Research conducted at the USDA-ARS in Madison, WI found that sfe corn silage had improved NDF digestibility and so resulted in greater dry matter intake and milk yield. This is a different mutation than brown midrib (bmr) which lowers the content of lignin in the corn plant. Four bmr mutations exist for corn (bmr 1, 2, 3, and 4), with the bmr3 being marketed for many years. In 2012, bmr1 corn will also be sold, so now farmers will have a choice among these low-lignin corn silages. Research is needed to fully assess the nutritional and agronomic differences between these two bmr mutations. We know from extensive research with sorghums that “bmr is not bmr” and that substantial differences in composition and fiber digestibility may exist among them, but it is exciting to see more potential sources of digestible NDF from corn silage available for dairy farmers.

Another promising research study comes from the scientists at the Noble Foundation in Oklahoma, a well known plant science institute. These researchers have found a potential approach for overcoming the reduction in yield associated with genetic modification to reduce lignin in alfalfa and thale cress. They found that the plant stress hormone salicylic acid is inversely related to lignin levels and plant growth. These researchers propose developing plants in which production of salicylic acid is blocked and consequently, growth of low-lignin alfalfas would be normal. They have developed an experimental system that allows them to attempt just that.

As you can tell, there is a lot more to these scientific stories than I’ve captured here, but the bottom line is that we are on the threshold of dramatic improvements in the nutritional value of our major forage crops. In the coming years, we should have corn and alfalfa forages with greater fiber digestibility, improved protein quality, and better agronomic performance. What an exciting time to be feeding ruminants!

— Rick Grant

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The Miner Institute Farm Report is written primarily for farmers and other agricultural professionals in the Northeastern U.S. and Eastern Canada. Most articles deal with dairy and crops topics, but also included are articles dealing with environmental issues and global agriculture as well as editorial commentary.

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