Consideration of Fat and Protein in Alternative Feeds
By: Tara Felix, Penn State University
Cattle are tremendous creatures that can handle many feeds that non-ruminant animals, pigs and chickens, for example, cannot eat. Thus, beef cattle producers are uniquely positioned to use new and changing feed ingredients.
I was overwhelmed this Extension season by the interest in alternative feeding strategies. Particularly when corn prices are down. It seemed like every talk I gave this year focused on this topic of what can we feed cattle other than corn? The answer can become pretty lengthy actually.
In my opinion, one of the greatest thing about being a beef cattle nutritionist is the variability in my job. Cattle really are tremendous creatures and can handle many feeds that nonruminant animals, pigs and chickens, for example, cannot eat. Thus, beef cattle producers are uniquely positioned to use new and changing feed ingredients. The key is getting an analysis and knowing what one is dealing with in order to continue to meet animal’s requirements. In this article, I’ll focus on 2 key things to watch for in your nutrient analysis: protein and fat.
I will start with protein. Whether we are supplementing cows or feeder cattle, historically, much of our alternative feeds, like distillers grains or corn gluten feed, have been used as a protein supplement. These feeds both contain a great deal of protein and worked well when fed to cows at about 3 to 5 pounds per head each day or at 2 to 3 pounds for growing feeder cattle. However, when corn prices began to climb in 2008, beef cattle nutritionist and producers sought ways to incorporate more of these traditional protein supplements in the diet to supply energy to the cattle. The problem is that excess protein in the diet can increase rumen ammonia concentrations and decrease feed intake (Waldo, 1968). In addition, there may be a cost to cattle performance if they are consuming large quantities of protein because they must be able to excrete the unused portion and there is a metabolic cost to that excretion (Reynolds and Kristensen, 2008). In addition to the cost of excretion, as responsible stewards of agriculture, the animal is not the only concern and the excess nitrogen that is then excreted into the environment must also be considered. For example, we know that more than 50% of the protein in DGS escapes ruminal fermentation (Waller et al., 1980; Firkins et al., 1984). This escape protein should be beneficial in meeting the metabolizable protein requirement of growing cattle. However, increased nitrogen excretion could lead to volatilization of ammonia into the atmosphere; in fact, as much as 42% of excreted nitrogen is lost to the environment (Eghball et al., 1997).
In addition to the protein in alternative feeds, fat concentrations can be another big issue. Whether we are considering feeding corn coproducts, bakery waste, potato chip waste, or chocolate, all of these alternative feeds can be limited in the diet because of their respective fat concentrations. We have long known that dietary unsaturated fat can decrease degradation of fiber in the rumen (Lucas and Loosli, 1944; Swift et al., 1947). Saturated fats, like lard or tallow, are admittedly less problematic. For example, when 6% supplementation with either unsaturated or saturated fat was compared, cattle fed the unsaturated fat diet had decreased hemicellulose and NDF digestibility when compared to those fed the saturated fat (Nelson et al., 2008). By limiting the inclusion of high fat byproducts in the diet, beef cattle producers can still use them, but decrease the risks associated with overfeeding fat.
The important thing to keep in mind is that just because you got a load of bakery waste that only had 20% fat in September, does not mean that a load from that same plant will necessarily be comparable in January. These alternative feeds are byproducts of the industries that they originate from. Thus, whatever waste needs disposed of is what is going in to the product. It may be sugar free, low-fat cookies one day and wedding cake with extra buttercream icing and whoopee pies the next! Be sure to get an analysis of your feeds.
