Expert Answers - July 19, 2013

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The following answer is excerpted from a paper presented at the 4-State Dairy Nutrition and Management Conference this past June by Mary Beth Hall, of the U.S. Dairy Forage Research Center, and Larry Chase, of the Department of Animal Science at Cornell University.

Q. Given tight forage supplies in many parts of the country, what is the potential of using forage substitutes in low starch/high byproduct diets?

A: Take-home message: Use of forage substitutes in low starch/high byproduct diets can maintain good milk production and components in late-lactation cows. Intakes increased, and feed efficiency and income over feed costs were lower than on a high forage/higher starch TMR. Dietary phosphorus contents were also greater than with the high forage TMR because of the byproducts used. There was a suggestion that feeding the highest amount of wheat straw may have increased mobilization of body tissues, so body condition should be watched carefully with these types of rations.

The drought has made this a challenging year. Feed prices are high and forage may be limited in both quality and quantity. So, what are our options for feeding cows? We know that dairy cows need fermentable and physically effective feeds to provide nutrients and maintain good rumen function. Common forage substitutes such as sugar beet pulp or straw provide either very fermentable or very physically effective fiber sources, respectively. In dealing with high feed prices, replacement of purchased corn grain or soybean meal with less expensive by-product feeds could reduce cost of the ration. However, a challenge is that formulating rations based largely on forage substitutes and byproducts has not been well explored. Do they need more effective fiber to keep byproduct fiber in the rumen to be digested?

We ran an experiment to test some of the possibilities.

The objective of the feeding trial was to evaluate performance of lactating dairy cows offered different combinations of forage substitutes (wheat straw = more effective fiber, and sugar beet pulp = more fermentable) in diets that were relatively low in forage and supplemented solely with byproducts (no corn, no soy).

See the complete paper detailing the research design.

Summary

Late lactation cows maintained performance on the low forage, low starch diets based on byproduct feeds. Using up to 6 percent wheat straw gave good performance without noticeable body weight loss/condition change. If such diets are tried, cows should be carefully observed to assure that body weight is maintained. The high phosphorus content of the byproducts elevated phosphorus content in the diet; not desirable long term for nutrient management issues and impact on the environment. On the 60 percent forage “more standard” lactating cow diet, cows gave similar milk production performance, had lower intakes, more efficient production, and better income over feed costs than cows on the experimental diets. However, the forage substitute/high byproduct diets are viable substitutes to feed lactating dairy cows when other more traditional feeds are in short supply.



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