From both an economic and environmental standpoint, dairy farmers and their nutritionists need to think outside the box when it comes to sources of nutrients that cattle can consume.
By Gail Carpenter, PhD What are we referring to when we refer to alternative feeds? Since the ancestors of our modern dairy cows were designed as grazers, in a sense it could be argued that all feeds besides pasture should be considered “alternatives.” Generally speaking for the purposes of this article, however, alternative feeds are defined by whether they are alternatives to North America’s traditional concentrate feeds (e.g., corn and soybean meal) or alternatives to traditional forages (e.g., corn silage and alfalfa). Alternative concentrates will generally include byproduct and coproduct feeds, and alternative forages include either biomass crops or cover crops. These alternatives provide an opportunity for farmers and nutritionists to get creative with their rations. Even in normal economic times, feed represents one of the major costs on a dairy farm. Certainly, in today’s economy, feed has become an increasingly critical cost that must be controlled to optimize farm profitability. One of the advantages of the ruminant is that she is able to consume nutrients that are unavailable to or ingredients that are unpalatable for human consumption and recycle these into high-quality human edible (HE) protein and energy sources. This has obvious implications for feed costs since she can digest and utilize lower cost feeds, but also on the sustainability of the dairy industry. Alternative feeds for a more sustainable industry Although ruminant digestion has its benefits, it also has its downsides. For example, the conversion of feeds such as corn silage, legume or grass forages, and traditional concentrate feeds to milk for human consumption can represent an inefficiency in the system. A common critique of animal agriculture is that some of these feedstuffs—particularly corn and soybean meal—could be consumed by humans directly without needing to be consumed and digested by the ruminant first. Furthermore, the land that is used to raise these feedstuffs for livestock production could be used to directly produce high-quality food for human consumption. While this critique may have some inadequacies, it does represent an opportunity for the dairy industry as we continue to strive for more sustainable food production.
One option for limiting the resource use footprint of dairy production is to use feedstuffs that do not compete with human food production. Alternative feeds provide a way of doing this. For example, feeding byproduct or coproduct feeds that would otherwise be wasted from human food or biofuel production can replace traditional concentrates in the diet. From a forage perspective, cover crops have the benefit of improving soil health and can also be a source of fiber for dairy cattle. Biomass crops can often be grown on marginal land, and thus may be grown on land that does not directly compete for human food production. One way to quantify this impact on dairy production’s footprint is by measuring the HE energy or protein output divided by the HE energy or protein input. Cattle can be net producers of HE energy or protein, meaning that they put out more energy or protein for human consumption than they consume in feed. However, the story is more complicated than this. In a paper published by Takiya et al. in 2019, the authors showed that the assumptions that researchers make have a major impact on the measurement of HE output/HE input. For example, in one experiment, the authors fed a traditional diet consisting of corn silage, alfalfa hay, corn gluten feed, cottonseed, expellers soybean meal, and ground corn. They compared this to a byproduct diet that consisted of corn gluten feed, wheat straw, wheat midds, hominy, molasses, blood meal, and algae residue. They measured milk energy and protein output, but they tested different assumptions regarding which of the feeds were actually human edible.
In a “thrift” scenario, they considered that in times of extreme hunger, the hominy and wheat midds may actually be consumed by humans for some amount of energy and protein, and they compared this to a “choice” scenario, where it was assumed that wheat midds and hominy did not provide HE energy or protein. In a third scenario, called “land use,” they considered that in a thrift scenario, land used to grow alfalfa hay could have been used to grow more HE food. In all cases, there was a benefit of feeding more byproduct feeds on the measurement of HE outputs over HE inputs; however, the differences were more nuanced in the thrift and land use scenarios. Furthermore, the authors found that in this experiment, feed efficiency was decreased, meaning that its economic benefit for the dairy producer is less clear. In a second experiment in the same paper, researchers tested another byproduct diet. In this experiment, the traditional diet consisted of corn silage, alfalfa hay, prairie hay, corn gluten feed, cottonseed, ground corn, and expeller’s soybean meal. The byproduct diet was made of triticale/clover hay, corn gluten feed, ground corn, wheat midds, hominy feed, spent coffee grounds, and molasses. In this comparison, the byproduct diet significantly decreased dry matter intake as well as milk yield. As a result, under thrift conditions, the byproduct diet had less HE energy and protein output over inputs compared to the traditional diet, and this was even true when amino acids were balanced with protected sources. The lesson here is that for diets with high levels of alternative feeds, production and efficiency are still important from both an economical and sustainability perspective. Practical considerations for alternative feedstuffs When it comes to alternative feeds, research data has not adequately addressed all of the options available to producers, so it is likely that a farmer or their nutritionist may have the opportunity to feed an ingredient that has not been researched previously. When this happens, it is important to keep in mind the basics of good feed management. Remember that cows have requirements for nutrients, not ingredients, but that the physical form of the feed will be critical if she is going to consume that feed as part of her TMR. In other words, to the rumen, the nutritional composition of a feedstuff is more important than the ingredient itself, but if the cow physically will not eat that ingredient, the rumen will never have a chance to digest it. For example, if the particle size is too large and the feedstuff is unpalatable, the cow will likely sort this out.
Gail Carpenter, PhD, is assistant professor, Dairy Extension & Outreach at Iowa State University.
Other common issues include variation in nutrient composition and difficulties with storage. It is important for producers to work closely with their nutritionists when evaluating the usefulness of these feeds in their production systems. For forages in particular, consider that all forages can be useful on the farm, assuming that they are not excessively spoiled. For example, biomass crops are generally high quantity but low quality; thus, they may be useful for dry cows or heifers, but not in all lactating cow rations. In farms that feed multiple diets to lactating cows (e.g., a high cow and a low cow diet), there is additional flexibility to feed less digestible or lower quality forages to low cows, freeing up the high-quality forage inventory for high-producing cattle. As ruminants, dairy cattle are exceptional creatures that can create high-quality milk for our consumption from many different sources of nutrients. From both an economic and environmental standpoint, dairy farmers and their nutritionists need to think outside the box when it comes to sources of nutrients that cattle can consume. The options are limitless!
