ISSUE FOCUS 20 FEED & ADDITIVE MAGAZINE March 2022 How can dietary tweaks support feed efficiency? More digestible feeds release more energy and protein to the animal which supports better feed efficiency. Improved understanding of the role that dietary, metabolizable protein plays for lactating dairy cows has established a relationship between protein in the diet and milk yield. When considering protein in the diet certain protein elements are especially valuable for supporting ruminal microbes. Ammonia, amino acids, and peptides (short chains of amino acid) are important. Sources of these acids include rumen degraded microbial protein, rumen undegraded protein and rumen protected amino acids – a more expensive option. While several amino acids are considered essential, they are not provided at required levels within most feed ingredients. Typically, a feed ingredient will have some, but not all of the amino acids. Rumen-protected amino acids are costly but potential benefits can include an increase in milk protein levels, an increase in overall milk yield during lactation and higher milk fat levels. Milk urea nitrogen is a measure of the cow’s ability to capture nitrogen originating from ongoing microbial protein synthesis in the rumen. The process measures the amount of ammonia processed by the liver, that becomes trapped in the milk. If levels are too high, the result can be reduced nitrogen efficiency and both fertility and rumen function may start to decline. Trace minerals provide an interesting option for supporting feed digestibility. Careful attention to the trace minerals included in a cow’s diet can have a big impact on rumen function and thus the digestibility of the dairy cow’s diet. How does trace mineral management support rumen performance in dairy cows? Trace minerals are an essential part of ruminant rations. As the basal diet does not supply these essential nutrients at adequate levels, they must be supplemented. But not all trace minerals sources are the same and the source of trace mineral has been shown to play a big role in how much of the mineral is available for use by the animal. Sulphate trace minerals have been used as a source of trace mineral supplementation in ruminant rations for the past 75 years. They are also commonly used in footbaths because they readily release trace metal ions known to be antimicrobial. While this mode of action is good in footbaths where free metal ions can detach and attack hoof related infections, such properties are highly undesirable in the rumen. Inside the rumen, sulphate salts are highly soluble upon contact with moisture, followed by their release of high concentrations of free metal ions that can now attack rumen, fiber digesting bacteria. Additionally, as trace minerals break down following contact with moisture, they can interact with other essential ingredients and additives in the feed, potentially reducing the value of costly feed ingredients. What can farmers do to protect their herds and their business from the challenges posed by sulphates? Choosing a trace mineral source that is not soluble is a good first step in preventing the harm posed by sulphate minerals. Hydroxy forms of trace minerals are largely insoluble at a pH of 4 or higher. As the rumen pH of dairy cattle is typically in the range of 6 to 6.5, hydroxy trace minerals are essentially insoluble (inert) within the rumen. In the abomasum, where the pH is usually below 3, Intel-
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