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Reducing Greenhouse Gas Emissions Through Rations and Diet Formulation

As ruminants, cows naturally produce methane as they digest food, making enteric methane one of the largest sources of greenhouse gas (GHG) emissions in the dairy sector. Farmers have several options available today to reduce these emissions, such as improving feed quality and optimizing herd management practices. Additionally, innovative opportunities, including the use of feed additives and genetic selection, are being explored to further mitigate methane emissions in the future. These advancements will help the dairy industry continue to reduce its environmental impact and contribute to more sustainable agricultural practices.

Learning Hub  Dairy Rations

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Summary Presentation

SPEAKER: Dr. Mary Beth de Ondarza

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Summary of Key Points from the Presentation

Dairy Cow Rations

As ruminants, cows have four-compartment stomachs to digest their diet. The rumen is the main fermentation chamber, breaking down food with the help of microbes. The rumen and its microbes are a carefully balanced system within the cow.

 

Dairy cows are fed specially formulated diets that aim to balance protein, fiber, starch, sugar, and fat. Many farms feed a total mixed ration (TMR) that contains all the feed and nutrients the cow needs. This is an efficient and profitable way to feed dairy cows. ​​​​

Using Byproducts

Cows are excellent recyclers! The diversion of food waste from byproducts to cow diets reduces emissions by 4.7-fold compared to composting and 49-fold compared to putting these wastes in landfills (de Ondarza & Tricario, 2021). By feeding byproducts to cows, ingredients that humans cannot or will not utilize are transformed into nutritious food for human consumption. The availability and type of byproduct ingredients varies across regions of the U.S.

  • Common byproducts: corn distillers grains, canola meal, and soybean meal

  • Less common byproducts: citrus pulp, bakery waste, candy, beet pulp, and almond hulls

Related Practices Or Technologies

Optimizing Diets

U.S. dairy producers have greatly increased the amount of milk produced per cow over the last century. Part of this increase is due to better diet formulation and adjusting diets to support high production levels. Dairy nutritionists have done a great job formulating diets that meet the nutritional requirements of high-producing dairy cows, thereby reducing the GHG intensity per unit of milk. The next step will be to decrease enteric methane emissions directly through diet.

DIET COMPONENT & EFFECT

Fats and Lipids

  • Supplementation of fats in the diet can decrease enteric methane emissions by:​

    • Directly inhibiting microbes that produce methane.

    • Providing an alternative hydrogen sink to reduce the pool of hydrogen that needs to be converted to methane.

    • Reducing fiber digestion to decrease hydrogen production.

  • Unfortunately, excessive amounts of dietary fats, especially certain fatty acid types, can reduce fiber digestion and milk fat production by the cow.

Forages

  • High-quality, highly digestible forages help to increase milk production and, thus, lower emission intensity​.

Fiber

  • Ensuring cows get enough effective dietary fiber helps to maintain rumen health and reduces undigested starch passing out in manure.

  • Excess starch in manure can result in more methane production from microbes in manure pits​.

Starch

  • Unlike fiber fermentation, which yields more acetate, butyrate, and hydrogen, starch fermentation favors the production of propionate, resulting in less hydrogen that needs to be disposed of as enteric methane. In this way, feeding higher starch diets can reduce enteric methane.

  • Increasing dietary starch typically results in a higher proportion of feed digested in the intestine rather than the rumen. Furthermore, higher dietary starch usually increases milk production to reduce GHG intensity per unit of milk.

  • Care must be taken with increasing dietary starch since this strategy can have a negative effect on rumen pH, nutrient digestion, and milk composition.

Protein

  • ​Lowering total dietary protein while balancing diets to supply specifically needed amino acids can allow us to more precisely feed what the cow needs to make milk. Excess protein is expensive waste and becomes nitrous oxide (a GHG) in manure.

  • We can also reduce nitrogen waste by providing multiple sources of protein and carbohydrates in the diet that break down quickly and slowly so that the rumen microbes can most efficiently convert nitrogen, protein, and carbohydrates into rumen microbial protein to be absorbed and used by the cow.

  • An additional motivation for balancing nutrients, like nitrogen and phosphorus, in the diet is that excess nutrients that are not utilized by cows end up excreted and can make their way into water systems.

Related Practices Or Technologies

Improving Feed Management

Formulating a diet is only one part of feeding cows! There are many steps between the ration formulated by a nutritionist and what the cows actually eat. Following best feeding management practices is key for achieving high production. 

Examples of how to improve feed management:

  • Add feed to the TMR mixer in the correct order.

  • Make sure mixer scales are calibrated.

  • Ensure correct mixing time and particle size.

  • Monitor changes in feed dry matter.

  • Push feed up regularly to reduce sorting.

Related Practices Or Technologies

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Please note that we cannot confirm the accuracy or reliability of the materials found on external websites linked here.

How Farms Can Reduce GHG Emissions

What we feed cows — as well as how much of each dietary nutrient we feed — has an impact on GHG emissions. As dairy cows produce milk, they also produce byproducts with environmental impacts.

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  • Diet optimization: Optimizing diets can reduce enteric methane emissions.

  • Nitrogen management: Reducing the amount of nitrogen excreted can reduce manure and urine-associated nitrous oxide emissions.

  • Rate adjustments: Optimizing the rate of feed passage and digestion can maximize the nutrients used for milk production and reduce emissions.

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