| For the copper requirement, did the Mo/S ratio remained the same, or was there a change in the Mo/S ratio from 2001 to 2021? |
The Mo and S ratio will not affect the requirement, but it will affect the AC. We did not have confidence in current data to quantify the antagonism in the software, however the text discusses possible adjustments to the AC based on diet S and Mo. |
| Based on what criterion or criteria is the adequacy of dietary P supply assessed in dry dairy cows? |
The P requirement for dry cows is calculated using the factorial method and would include endogenous fecal (a function of DMI) and P in the conceptus. Those requirements are well established and for the average dry cow will be accurate. The AC of P is also known pretty well, so estimates of dietary P requirement are accurate. Low plasma P ( <2 mg P/dL) can indicate inadequate P but that is often complicated with hypocalcemia which can make the interpretation of blood data difficult. If cows are clinically normal but have low blood P then they probably should be fed a little more P but in the vast majority of cases, NASEM requirements for P should be adequate.
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| What do you think about the study of Bouwstra 2008 regarding Vitamin E regeneration where 3000 IU has been found hazardous due to lack of co-oxidants to regenerate Vitamin E itself? |
The Bouwstra study found increased mastitis with high E (3000 IU/d) for the entire dry period. I have some issues with how they defined mastitis, but it was a large study (lots of farms and cows). The study clearly shows no benefit from high E supplementation for the whole dry period but additional studies are needed to confirm the increased mastitis incidence. Most studies with vit E supplementation show reduced mastitis but Bouwstra fed very high amounts for a long period of time. Any antioxidant can also function as a pro-oxidant if excess is fed and the same is true for vit E. |
| Why is there a difference in AC between inorganic P and organic P in the small intestine as organic feed P may transfer to inorganic P by microbial breakdown |
Some dietary inorganic P will be converted to organic P in the rumen. The AC shown in the talk assumes a certain amount of conversion based on a published model of P metabolism (JDS 98:7194). |
| How much ratio between minerals, is it the same for Zn and Cu and other minerals? |
The old NRC, or new NASEM dairy does not establish any set ratios between various essential trace minerals. Dairy animal requirements are based on a factorial approach that considers how trace minerals are being absorbed, retained, and excreted by the dairy animal to arrive at an approximate requirement for individual trace elements. |
| In a past publications, it has been recommended that it may be beneficial to increase NRC 2001 trace mineral requirements a bit (typically 10 – 20%). Do you continue to believe that the new NASEM 2021 requirements should be adjusted upward as well? |
As mentioned in the presentation, trace metal requirements for dairy animals have been arrived at via a factorial approach to derive a requirement that is based on the mean of all data reviewed, plus a correction factor of 1.2. If dairy animals are experiencing periods of heavy stress (environmental, nutritional, health, etc.) it may be prudent to consultant your nutritionist concerning the need to increase trace mineral feeding levels or an improved source of trace mineral. |
| Can you comment on how requirements for Cu supplementation will change in the presence of high levels of antagonists such as Mo and S in grazing swards? |
Higher levels of Mo and S can significantly reduce the availability of Cu in the animal due to the formation of thiomolybdates, which binds the Cu, Mo, and S in one indigestible molecule. The best action to counter this situation is to reduce the level of both Mo and S in the diet by eliminating high Mo/S ingredients and or diluting the diet's Mo and S levels via the use of alternative ingredients. |
| If a producer, or their nutritionist who is following the new NASEM Dairy 2021 recommendations decides to move from sulfate trace minerals to an improved trace mineral source, hydroxy, or organic, should the amount of metal supplied to the diet be reduced to compensate for product's increased bioavailability? |
The new NASEM Dairy 2021 uses sulfate trace mineral sources as its default source of supplemental trace mineral supplementation. As a result, the amount of supplemental trace mineral required is formulated based on its assigned AC (copper sulfate = approximately 5%). If an improved source of trace mineral is utilized to replace the sulfate source, its higher AC may be used, resulting in a reduction in the actual amount of supplemented trace mineral originating from the improved trace mineral source supplied to the animal. |
| How will the basal diet influence trace mineral requirements, and the interaction between minerals? |
The majority of trace mineral that exist within various basal ingredients are in an organic trace mineral form preventing any major antagonisms between basal ingredient trace minerals. It is only after they are digested within the cow that trace minerals become susceptible to various antagonisms. As the new NASEM points out the trace metal levels of all basal ingredients must be considered when formulating dairy diets. Where possible it is best to have basal ingredients assayed using wet chemistry to determine actual trace metal levels in high volume basal ingredients (silages, hay, etc.), allowing for greater trace metal formulation accuracy. |
| How can injectable Vit E and Se administration be adjusted in addition to the premix inclusions? |
The recommendations developed within the new NASEM for the supplementation of Se and Vitamin E are sufficient to meet the needs of a typical dairy cow. This is not to say that a cow experiencing periods of stress may not benefit from an additional injection of Se / Vit E. Best to consult your veterinarian or nutritionists to determine the correct protocol if additional supplementation is warranted. |
| Recent research has indicated the negative impact of more soluble, sulfate-based trace minerals on rumen fiber digestibility. Based on this data should sulfate trace minerals be avoided in dairy diets? |
This data was not considered by the NASEM committee due to its recent release, however recent research does indicate that sulfate-based trace minerals (Zn and Cu) appear to be negatively affecting rumen fibre digestibility. This appears to be due to the antimicrobial effects of zinc and copper sulfate when entering the rumen thereby negatively affecting rumen fiber digestibility. |
