Straw - Golden opportunity
Much more than just a bedding material, straw has proven its worth as a valuable fibre source in lactating and dry cow feeds
When it comes to your dairy herd's diet, fibre takes on the lustre of pure gold. It can increase butterfat tests in the milk you ship and improve feed efficiency by helping stabilize the cows' rumens to use other nutrients more efficiently.
You can spin straw into gold for your total mixed ration (TMR) when you chop this unconventional fibre source to the right length and add it in the right amounts.
In dry cow and transition cow diets, straw lets cows maintain their pre-calving dry matter intake. It contributes to gut fill-water and feed residue in the digestive tract-thus reducing displaced abomasums at calving. Cows can eat all the feed they want, without getting too much energy.
Securing enough fibre for your lactating cows could be a challenge as corn prices increase and more land goes into growing grain instead of hay. If your current ration lacks enough effective fibre or fibre sources are scarce, straw can help fill the void.
Straw can provide physically effective neutral detergent fibre (peNDF) to get cows chewing. It also contributes to that floating mass of particles in the rumen. Compared with 34 per cent peNDF in corn silage, straw provides about 52 per cent.
Straw versus corn silage
In a recent study, Mary Beth Hall, a researcher at the U.S. Dairy Forage Research Center in Wisconsin, compared the fibre value of chopped straw versus that of corn silage in feeding dairy cows.
She investigated four diets: wheat straw with high-moisture shelled corn; wheat straw with dry, ground corn; chopped and ensiled cornstalks with high-moisture shelled corn; and chopped and ensiled stalks with dry, ground corn. Other ration components included alfalfa haylage, corn silage, soybean meal, roasted soybeans, soy hulls and a vitamin and mineral mix that contained monensin.
All diets matched nutritionally, at 31 per cent NDF, with 25 per cent of ration dry matter coming from forages, 26 per cent from starch and 17.5 per cent from crude protein. The cows ate about 22 kilograms of feed per day, including 2.7 kg of either straw or corn silage. All animals rotated through the diets over the two month trial.
During this period, the cows spent the same time eating and ruminating regardless of diet. Milk production stayed the same, as well. Production averaged 37 kg of milk, with 3.8 per cent butterfat and 2.9 per cent protein.
Higher MUN levels
Milk and protein yields were slightly higher for cows eating corn silage. Milk-urea-nitrogen levels were higher for animals on the wheat-straw diets, Hall found.
The corn silage diets appeared to move feed through cows faster. The wheat straw diets tended to remain in their rumens longer. This might lead to more efficient digestion of nutrients in the diet.
Straw is typically put into a ration at a rate of 2.5 to 5.5 kg per head per day. If you are going to feed straw in the ration, however, don't assume book values for it. A study looking at straw values found analyses ranged from 20 to 40 per cent NDF digestibility.
Analyse before feeding
Use wet chemistry analysis for dry matter, crude protein, NDF, NDF digestibility, fat and ash to be able to calculate energy available. Straw's crude protein will typically be less than five per cent, while NDF will be greater than 75 per cent and total digestible nutrients less than 45 per cent.
If you source straw from an underseeded wheat crop and it has significant alfalfa or new seeding mixed with it, the straw's nutritional quality could be impacted. Protein, energy and potassium may be much higher than anticipated.
Chop straw to a length of two inches or less. However, chopping to less than one inch can defeat the purpose of providing effective fibre.
Sorting poses a major challenge to feeding straw in a TMR. If your cows sort the straw out of their feed, they will not get the fibre the ration calls for. A dairy ration should include just over 20 per cent of its NDF from forage dry matter intake. By making sure the TMR amount fed per day is matched to the cows' daily intake, you can reduce sorting's impact.
Also beneficial is ensuring the TMR is at proper moisture levels. You may have to add water to help stick the straw and other ingredients together.
Straw's benefit to the ration depends on price and availability. Higher grain prices and land use pressures could make it a golden opportunity.
This article first appeared in the September 2011 Ruminations column of the Milk Producer magazine.
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