Animal protein (animal byproduct meals) sources have been used in dairy cattle feeding programs for years. Products such as blood meal, fish meal, meat and bone have long been known for their ability to supply rumen-undegraded protein and, more recently, metabolizable protein and critical amino acids (lysine, methionine).

As we understand these protein components that are possibly more effectively and efficiently used to meet the requirements of the dairy cow, one might see a potentially greater demand for animal protein sources. Unfortunately, reality may be more complicated.

Animal protein sources come from a variety of food animal processing industries. Due to the bovine spongiform encephalopathy issues and subsequent regulation and restriction of these products from the cattle industry, we see these sources coming from pork, poultry and aqua (fish) production industries. Table 1 illustrates several of the nutrients of interest for these products.

Example nutrient values for animal protein sources (dry matter basis)

As noted, these are “example” nutrient values. There is a great deal of variability of values from species to species, source to source and lab to lab. It is important that sources be analyzed regularly to ensure accurate values are used in specific diets.

The challenges faced with using any of these products, as a commodity, can be numerous. These can include:

  • Cost – Most of the animal proteins, despite the fact that they are byproducts from the processing industries, tend to be expensive. This is relative since we normally do not use these materials as a source of “conventional” nutrients such as crude protein or crude fat.

  • Cost volatility – It is not unusual to see significant swings in pricing of these materials. These ingredients are commonly used in other-species feeding as well – poultry meal is commonly used in the pet industry and fish meal is used extensively in aquaculture diets – thus a variety of market-affecting factors can come into play. Processing schedules can play a role in market prices as well.

  • Feeding rate/palatability – Feeding of some of these products must be handled carefully to prevent dry matter intake depression. In many cases, a maximum of about 1 pound per head per day is recommended.

  • Fat content – Some products are high in fat which, when fed, can potentially result in milkfat depression if overfed.

  • Fat rancidity – Unless treated with an antioxidant, and if not fed in a timely fashion, fat components can become rancid.

Blood meal is one of the most commonly used lysine sources in dairy cattle diets to meet amino acid needs. However, when fed as a commodity, blood meal is often characterized by inconsistency and variability.

Also, the source of blood meal from either porcine or poultry sources has been brought into question. There is some evidence that suggests poultry blood meal is less digestible by the dairy animal when compared to pork blood meal.

Trials at the University of Minnesota have illustrated the variability of lysine levels in blood meal. One study compared four samples of blood meal for lysine percentage, percent rumen-undegraded protein, percent lysine digestibility and percent metabolizable protein in the lysine.

Lysine digestibility is one of the most important values because it shows how much of the lysine can be utilized by the cow.

The average percent digestibility was reported as 65.6 percent in the four blood meals tested, while it ranged from 53 to 80 percent. The range makes it especially difficult to consistently balance rations for amino acids using blood meal.

We can compare these values to other sources as well. In the 2001 Dairy NRC, the actual blood meal lysine values were based on the analysis of 53 samples with standard deviation of 0.34. The actual source of blood meal (porcine or poultry) is not reported.

By the same token, the NRC standard deviations for lysine for feather and meat and bone are 0.35 (N=156) and 0.42 (N=227) respectively for products much lower in lysine.

This range in quality parameters is concerning because cows depend on consistent, high-quality protein delivery in the diet to maintain high production levels. If the amino acid levels provided by blood meal (or other animal protein source) are different from load to load, it is very difficult, if not impossible, to properly balance the diet.

Finding a high-quality lysine or other amino acid source is critical to deliver consistent, high-quality protein cows need to optimize production and efficiency throughout lactation. Alternative sources to blood meal can provide similar nutrients along with consistent levels of lysine for peace of mind and peak performance.

This is one reason some nutritionists have used some of the commercial animal protein blends.

Several companies manufacture blends, both custom and proprietary, where a certain degree of a quality assurance procedure is applied to help reduce the variation of certain nutrient values. The question becomes: Is the added cost of the commercial blended product worth the reduction in variation?

The use of a blend could help in fine-tuning the nutrient delivery. So with the nutrient fine-tuned, and variation reduced, the product value could be realized despite the added manufacturing margins. This would have to be evaluated on a case-by-case basis.

Additionally, with current formulation models focused on balancing for metabolizable protein and lysine, methionine, these products (commodities and manufactured) are seen as specific sources for these nutrients.

This has opened and expanded the market for synthetic rumen-protected amino acid sources. In many cases, the use of a rumen-protected amino acid in these models is a replacement for animal protein sources as an amino acid supply.

As a point of discussion, however, some nutritionists feel that synthetic sources of lysine or methionine are inferior when compared to “natural” sources when actual animal performance is evaluated. Research is needed to evaluate this perspective.

Consumer perception

Yet another long-term consideration for the use of animal proteins comes from the consumer perception of the use of such products in the food supply. Over recent years, consumers have become much more vocal as to what they consider acceptable (organic, no hormones, GMO-free, etc.).

There are marketing and production programs in place and growing in acceptance that promote all-vegetable (plant) feed sources for meat- and milk-producing animals. Some countries have also begun restricting animal proteins (in some cases only certain species) for import or domestic use in general.

No doubt the U.S. dairy industry will see increased pressure to reduce or eliminate the use of animal protein products in coming years.


For the time being, the uses of animal protein sources are available and fairly widely used by the dairy feeding industry. As we learn how to reduce or at least compensate for the variation, as well as understand the role of the many protein components, we may see opportunities to expand the use of animal proteins.  end mark

Stephen Blezinger