Table 2 – Rumen protected methionine meta-analysis.
D.M.I. (kg/d) Milk (kg/d) True milk protein (%) True milk protein (g/d) Milk fat (%) Milk fat (g/d) Adapted from R.A. Patton, 2010
3. Calculate Lys requirements (calculate Met first, then Lys) The first step when formulating is to maximise the output of energy and microbial protein from the rumen. 4. Balance on Energy Corrected Milk 5. Keep rumen N over 115% of requirement to cover rumen needs
6. Maximise microbial MP with fermentable CHO 7. Keep Lys/Met ratio at 2.7
Different methionine supplements Methionine supplements can be divided into lipid matrix and coat protected products. Lipid matrix sources rely on fat as the carrier of the methionine. They are cheaper than coat protected products, deliver a lower payload of methionine and have limited post-ruminal release and absorption. Therefore, most nutritionists and producers rely on coat protected methionine sources rather than lipid matrix products. True protected methionine products rely on a coat protection to bypass the rumen. The most known products worldwide are Mepron with ethylcellulose coating and pH sensitive rumen protected methionine (RPMet). Different products rely on different coatings and methods of releasing the methionine. Mepron works based on soaking and abrasion and releases methionine slowly, whereas pH sensitive RPMet releases methionine quickly in the abomasum. The quick release of pH sensitive RPMet causes a very marked but short-term methionine spike in the blood. Ethylcellulose coated RPMet with its slow-release properties causes no spike, but elevated methionine blood concentrations over a longer period. There is no correlation between the blood spike attained with pH sensitive RPMet
and higher milk protein yields. A study on market-available protected methionine products involving both pH sensitive and ethylcellulose RPMet is the meta-analysis published by Patton involving a database of 36 studies (Table 2). Cows fed Mepron produced more milk protein (37 vs 16g) and more fat (24 vs -2g) than those fed with pH sensitive RPMet. Cows fed Mepron also increased milk production (350 g/d) whereas those fed pH sensitive RPMet showed a reduction (-220 g/d). Mepron-fed cows increased milk protein yield and milk fat yield, as well as total milk production. Also, with higher milk production a dilution effect occurs. This means milk protein % is not sufficient to discriminate among products, and likely total production of milk protein or Energy Corrected Milk (ECM) are better measures of product performance.
Knowing your product Use of rumen-protected methionine, coupled with maximising microbial protein, is a valid strategy to increase milk production and farm profitability. Be aware of other possible metabolic roles of methionine that could disguise the beneficial effect of the amino acid, and bear in mind the importance of an adequate supply of energy as the first condition to successfully implement the use of protected amino acids. Choosing a reliable source of protected methionine is not easy. A product must be supported by abundant reliable scientific literature demonstrating its effects, and a long-time presence in the market, so practical experience is important. Methionine blood concentrations can be misleading, and it is not advisable to choose products based on it. A high blood concentration ‘spike’ only gives information about how methionine is released by a product, but a lower, more sustainable elevated blood methionine concentration is more desirable. Available meta- analyses show consistent, improved practical results by products following this strategy.
▶ COW HEALTH | AUGUST 2020 21
Product Mean Effect Ethylcellulose RPMet pH sensitive RPMet Ethylcellulose RPMet pH sensitive RPMet Ethylcellulose RPMet pH sensitive RPMet Ethylcellulose RPMet pH sensitive RPMet Ethylcellulose RPMet pH sensitive RPMet Ethylcellulose RPMet pH sensitive RPMet
-0.10 0.04 0.35
-0.22 0.06 0.08 37 16
-0.01 -0.02 24 -2
Q NS NS
<0.001 NS NS NS NS NS NS NS NS NS
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