Feeding byproducts from production, postharvest and processing of foods and other agro-industrial products to dairy cows has been routine practice for decades. Byproducts streamline diet formulation and constitute, on average, 30% of Midwestern dairy diets.
But this practice has been of utmost importance to dairy operations these last couple of years. Besides providing options to adjust dietary nutrients, feeding byproducts reduces feed costs and aids navigating through low forage inventories.
Corn gluten feed, brewers grain, whole cottonseed, wheat middlings and straw, cottonseed and soy hulls are some examples of options to stretch forage inventories when challenging weather conditions impair the optimal production, harvesting, and storage of forages. These byproduct feeds have considerable amounts of NDF and help fulfill fiber requirements of dairy cows.
But depending on their physical form, these feeds may lack physically effective fiber. Physically effective fiber stimulates chewing and salivation, rumination, gut motility and health, and is the structural basis of the ruminal mat. If the effectiveness of the fiber is too low, adjusting the amounts of rapidly fermentable carbohydrates fed is advised to reduce potential rumen health issues and milk fat depression.
Reducing feed costs
Reducing feed costs is the most common reason to feed byproducts. Nutrient estimates of a survey conducted with dairy nutritionists suggest byproducts provide, on average, 44 percent of the crude protein and 33 percent of the energy of Midwestern diets. But these numbers go up in periods which prices of corn or protein sources are high.
However, feed cost savings cannot be at the expense of performance. Dairy cows will often maintain production by increasing their dry matter consumption when fed diets with byproducts replacing corn. Income over feed costs is a better metric than feed cost alone as it accounts for these effects.
Estimating breakeven costs to determine which byproducts make sense purchasing is suggested. These estimates are based on nutrient concentration. Multiple tools are available without any costs, including the University of Wisconsin FEEDVAL which contrasts byproducts nutrient costs with other feeds.
Dealing with the challenges
Managing the storage and nutrient variability challenges associated with feeding byproducts is crucial. Wet byproducts, such as wet brewers and distiller grains, have a shorter shelf life. These wet feeds are especially unstable when they are exposed to oxygen and spoil rapidly. Shrink losses of up to 30% could occur.
Receiving loads of those wet feeds daily or multiple times a week circumvents this problem but increase transportation costs and nutrient variability.
Even though some byproducts are widely used for many years, monitoring the quality and consistency of these feeds is advised so nutrients are properly adjusted in the diet. This is because of the wide variation of raw materials and processing methods applied by different sources.
Using feed libraries as a starting point is fine so long as efforts are made to analyze nutrient composition. Checking byproduct feeds from industries not related to human consumption for mycotoxins is advised.
Changing diets, feeding management and storage facilities for byproducts with inconsistent availability or seasonal may not be justifiable due to additional time, management, and storage requirements.
Logistics of storing byproducts must be considered. Even though some byproducts can be stored in feed bins, others may require pits or large space within a commodity shed.
Feeding byproducts to dairy cows allows for the conversion of human-inedible sources into high-quality human-edible protein, such as milk. Otherwise, these byproducts from production, postharvest and processing of foods and other agro-industrial products would be composted, used for energy production, or disposed in landfill or by incineration.
Compared to composting and landfill disposal, research has estimated that feeding byproducts to dairy cows reduces greenhouse-gas emissions five and fifty times, respectively.
Luiz Ferraretto is a Ruminant Nutrition Extension Specialist for the University of Wisconsin – Madison