April 10, 2007

Experts weigh distillers grain use in US dairy rations
 

As the high price of corn continues to stir up US livestock, the other alternative in the form of distillers' grains as a less expensive option has several farm advisors from the University of California (UC) to analyse the nutritional aspects of the byproduct from the ethanol production process.

UC Dairy Farm Advisors Alejandro Castillo (Merced and Stanislaus Counties) and Gerald Higginbotham (Fresno and Madera Counties) have written their insight on a newsletter called "Dairy cows' nutrition: The Corn Grain Dilemma," that highlights insight on grain and distillers' grain issue.

The newsletter pointed out four critical factors to be considered to best use grains for lactating dairy cows.

1. Protein content: Distillers grains are a good source of rumen un-degradable protein. Degradable and un-degradable protein contents should be used to avoid a shortage of nitrogen in the rumen. Lysine is the first limiting amino acid in corn byproducts and is the most susceptible to heat damage.
    
   For this reason, lysine balances and insoluble nitrogen content should be evaluated to be sure that nitrogen and lysine are available for rumen microorganism and cows' metabolism. Positive results on milk protein content were observed when diets including distillers' grains were supplemented with lysine in lactating animals.
    
2. Fat content: The effects of oils and fats on rumen fermentation can vary, depending on other feedstuffs used. Adverse effects might be more likely when diets are based on corn silage or high fibre diets. Fat may have effects on rumen fermentation by reducing dry matter intake. In most situations, total dietary fat should not exceed 6 percent to 7 percent of dietary dry matter.
    
3. Mineral contents and balances: Sulfur should be monitored as sulfuric acid and is initially added in dry grinding at ethanol plants and to end the fermentation process. Excess sulfur in dairy diets may affect absorption of other minerals such as selenium and copper, decreasing animal performance, and in some situations affecting animal health and reproduction.
    
4. Distillers grain may be offered dried or wet: Due to post-fermentation problems, and depending on weather conditions, wet distillers grains (WDG) should be stored no longer than seven days. Also, a high concentration of mycotoxins could be expected if the original grain was contaminated. Propionic acid or other organic acids, or mycotoxins sequestering agents, should be used to control mycotoxins as necessary.

Storage in silo bags could be an option, but once opened, spoilage starts. It is expensive hauling wet distillers' grain in a long distance. Due to the high water content, rations may be too wet, affecting daily dry matter intake.

Castillo and Higginbotham said no more than 15 percent to 20 percent of a lactating cow's total ration, on a dry matter basis, should be composed of distillers' grain.

Excess protein and minerals in the diets may be result to animal health problems and environmental concerns such as air and water quality, according to the researchers.

They urged dairy farmers to develop a plan with a nutritionist before including distillers' grain in dairy rations.