White Paper: Soy products as partial replacements for alfalfa in dairy cow diets
Animal nutritionDairySoy hullsSoy meal
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
William Weiss, Weiss Dairy Consulting
Co-Principal Investigators:
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Brief Project Summary:
The goal of this project is to review the scientific literature on the use of soy products in dairy cow diets that contain little or no alfalfa and translate that information into a White Paper for non-scientists. Alfalfa is a good source of both protein and fiber and when inclusion rates are decreased, inclusion rates of soy products could increase to make up for the lost nutrients. Alfalfa inclusion rates in dairy diets are decreasing which is an opportunity for increased use of soy products in dairy diets. This White paper should help nutritionists incorporate soy products into low alfalfa diets.
Information And Results
Project Summary

Project Objectives

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Final Project Results

A technical paper was prepared on how soyhulls, whole soybeans, and various types of soybean meals can be used effectively in diets with little or no alfalfa. The advantages and limitations of using these products in low alfalfa diets were also discussed. Because of high production costs and agronomic challenges, alfalfa production in the US is decreasing which means the amount of alfalfa included in dairy cow diets is also decreasing. Alfalfa provides numerous nutrients to cows but the three that have the greatest economic value are metabolizable protein (MP), forage neutral detergent fiber (fNDF) and net energy (NEL). Soy protein sources can efficiently completely replace the MP provided by alfalfa. Because soy protein is more digestible than alfalfa protein the efficiency of converting crude protein (CP) to MP is greater when soy replaces alfalfa. This means diets with less alfalfa and more soy can be formulated to have lower concentrations of CP but will provide the same amount of MP. This often will reduce diet costs and will always reduce manure excretion of nitrogen. The MP/CP efficiency improvement may be even greater than expected as soy replaces alfalfa because of the composition of the rumen degradable protein fraction is almost exclusively peptides and proteins in soy which can be used more efficiently by rumen microbes to produce microbial protein tnan other forms of degradable crude protein. A primary reason alfalfa is included in dairy diets is because it provides high quality fiber that cows must chew and ruminate. Soyhulls are the only soy product that contains appreciable amounts of NDF, but it is NDF that does not elicit chewing (an essential process to maintain rumen and cow health). Therefore, soy cannot replace the NDF provided by alfalfa. However, soyhulls can be used to reduce starch concentrations in diets which reduces the requirement for fNDF. In many, perhaps most, situations where alfalfa is removed from diets, corn silage is increased. This will provide fNDF but it also provides starch. Because starch concentrations must be limited (~30% of diet dry matter) to maintain rumen and cow health, soyhulls are a useful ingredient in high corn silage, low alfalfa diets because they are moderate in NEL without increasing the starch load in the diet. Example diets that use soyhulls and soy protein to replace some or all of the alfalfa are included in the white paper.

Benefit To Soybean Farmers

This White Paper provides reasons and guidelines for using soy products in low alfalfa diets for dairy cows. Alfalfa acreage in the US has been trending down for decades and this trend will likely continue. This means diets with little or no alfalfa will become more common. Dairy cow nutritionists can use the information in this paper to effectively increase the use of soy products in low alfalfa diets. Ultimately this should increase the use of soyhulls, soybeans, and soybean meals by the dairy industry.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.