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Research is driving the forage industry forward

Dan Undersander Published on 12 November 2014

The highest milk-producing cow produced 72,000 pounds in 305 days. That is more than three times the national average. Some stockers have more than 4 pounds per day gain on forage. Such high animal performance requires re-designed forage.

The forage these animals need is forage with low and highly digestible fiber and with good bypass protein. The fiber component of forage is necessary because lack of fiber causes 42 percent of dairy lameness, either excessive grain or inadequate fiber. Yet the forage fiber must be highly digestible to provide the energy needed for high animal performance.

Legumes have lower fiber than grasses, and this is why alfalfa has become the foundation of the dairy industry. The problem is: Legume fiber is lower in digestibility than grass fiber. The reason for this is due, in part, to the higher lignin content of legumes.

Lignin in cell walls is necessary to give rigidity so that plants stand up (not lodge) and also to waterproof the plant vascular system to allow water conduct from the roots to the stems without leakage.

On the other hand, lignin is indigestible and reduces the digestibility of the cellulose. So we want as little lignin as possible to meet plant needs.

Thirty years of plant breeding have done little to reduce lignin content, but now, through genetic modification, we have been able to shut off a gene and reduce the lignin of alfalfa by 20 to 30 percent.

This reduced-lignin alfalfa will provide either improved forage quality when harvested at the same maturity as conventional lines or allow farmers to delay harvesting to achieve the same quality at a later date. I think the latter will be the most beneficial to most farmers.

If we can take three harvests instead of four, for example, we will reduce harvesting labor and increase yield perhaps 20 percent or more.

Further, it appears that the reduced-lignin alfalfa will give a wider harvest window (less rapid quality change), making it easier to get the desired quality.

It may also increase stand persistence since alfalfa is allowed to grow longer between cuttings and replace more root reserves. This trait is in the final stages of approval and expected to be generally available in 2016.

A second trait being worked on to improve the value of alfalfa is to increase the bypass protein. All alfalfa has high protein content but most of it is rumen-degradable, especially in haylage. This means that the high-quality protein of the forage is metabolized by rumen microbes and made into lower-quality microbial protein.

Decreasing the rate of protein degradation in the rumen increases rumen-undegradable protein (RUP or bypass protein) and increases protein use efficiency.

This means there is less need for bypass protein supplement, which is the greatest supplement cost for dairy cattle. So increased rumen bypass protein has great economic value to dairymen.

Some trials we conducted years ago also suggest that rapidly growing beef animals also have a high need for bypass protein. Most spring growth of forages is high in protein, but it is very rumen-degradable.

In the past, bypass protein supplement to growing beef animals was about an economic breakeven for the weight gain achieved. Now, with higher beef prices, the value of the grain would be much greater.

In addition, increased bypass protein in alfalfa would decrease dairy cattle nitrogen losses to the environment. When a highly rumen-degraded protein is fed to dairy cattle, it must be supplemented with bypass protein, and more nitrogen is excreted in the urine, which is detrimental to the environment.

Alfalfa has proteases that break down long protein molecules, especially during ensiling, and make the proteins more rumen-degradable.

A USDA Dairy Forage Research Center model showed that increasing RUP 20 percent to 30 percent would eliminate the need for protein supplements. It would also result in a 25 percent reduction in nitrogen losses to the environment.

Increased RUP would provide up to a 12 percent increase in net return for dairymen. This improved alfalfa would result in an increased value of alfalfa silage by $23 per ton.

Two approaches are being attempted to increase bypass protein. One approach is to make alfalfa more like red clover, which has greater protein stability in haylage than alfalfa.

Red clover produces an enzyme called polyphenyl oxidase (PPO). This enzyme uses a substrate, o-diphenyl, to form quinone. Quinone appears to inactivate proteases involved in alfalfa post-harvest proteolysis and result in more bypass protein.

The PPO reaction is similar to the browning reaction of a sliced apple. The red clover PPO gene has been isolated and moved into alfalfa.

However, there is no suitable substrate for the PPO enzyme in alfalfa. O-diphenyls occur in grasses, and it may be possible to mix the two species in silage and allow the PPO of alfalfa to use the o-diphenyl of the grass to produce quinones and increase the bypass protein of alfalfa.

The second approach is to increase tannins in alfalfa leaves. Tannins bind with protein, slowing the rate of rumen degradation and increasing RUP. Tannins occur naturally in birdsfoot trefoil.

Condensed tannins can be found in alfalfa seed coats but not leaves or stems. Genetic engineering can be used to turn on the tannin-producing genes already existing in alfalfa so tannins are produced in alfalfa leaves.

Much research needs to be done yet on this approach since the bypass protein depends on both the amount and type of tannins. Simply turning on the gene may result in too much tannin. Tannins reduce palatability so, if the tannin level is too high, the alfalfa may become unpalatable.

One other potential benefit of tannins is that bloat may be reduced for grazing animals. Tannins in birdsfoot trefoil are responsible for it being a non-bloating legume. Worldwide alfalfa-related bloat losses are estimated to be greater than $200,000,000. Thus, if the bloat potential of alfalfa were reduced or eliminated, the economic benefit would be great.

The two previous examples involve genetic modification. Traditional breeding efforts of alfalfa are ongoing to improve both salt and drought tolerance. Also, tremendous strides are being made to improve resistance to nematodes, a microscopic worm that exists in soils from the Midwest to the Northwest and Southwest U.S.

This resistance is appearing in new varieties now and will increase yield and stand life. Resistance is also being developed in new varieties of alfalfa for the new races of aphanomyces and for other diseases. The varieties released over the last few years have made tremendous strides in overcoming each of the aforementioned stresses.

Another area of development for alfalfa is the seed coating. Much research has been conducted to find beneficial coating compounds. Most seed is now coated with inoculum and with Apron, which reduces phytophthora, pythium and rhyzoctonia seedling death.

Now other fungicides are being evaluated. Minerals and other growth enhancers are also being evaluated. Some of the new coating products look very promising.

Research has changed alfalfa significantly in the last few years, and in the near future, changes will be even greater.  FG

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