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The role of methionine in transition cow health and milk production

Lyle Rode for Progressive Dairy Published on 29 March 2021

Methionine (Met) has been recognized as the limiting or co-limiting amino acid for milk production for many years. More recently, there has been a lot of interest in the benefits of supplementing methionine to transition cows as well.

During the transition period, cows are going through big physiological, dietary and endocrine changes that lead to compromised immune function, increased oxidative stress, increased tissue mobilization and nutrient requirements.

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More than being just an amino acid (AA) involved in protein synthesis, methionine has a unique, central role in almost all metabolic pathways and particularly those most active around parturition. Methionine is the key molecule involved in the transfer of “one-carbon” or “methylated” compounds in the body that are critical for cow health.

Choline supplementation has been used for many years to support fat metabolism and liver function in transition cows, reducing ketosis and improving milk production. Choline and methionine are linked because choline can provide some of the benefits of methionine, whereas methionine can be converted to choline in the body. Because of this relationship, there has been a lot of debate over the years as to which is more important. However, the more recent information points to specific, separate requirements for both nutrients, even though there is some overlap in their metabolic roles.

Newer research has demonstrated supplemental methionine has a multitude of positive effects beyond liver metabolism and ketosis. Post-ruminal methionine can increase prepartum and postpartum dry matter intake (DMI) and subsequently greater milk production, by up to 5 kilograms per day. In addition to improved liver lipid metabolism, methionine supplementation is associated with reduced inflammation and lowered oxidative stress, which will reduce the incidence of metabolic diseases post-calving and improve the cow’s ability to fight infectious disease such as mastitis.

One of the newer areas of nutrition is the impact nutrients have on the fetus and subsequent calf performance. The uterus and fetus account for up to 70% of the amino acid requirements pre-calving. Supplemental methionine up-regulates nutrient transporters in the placenta. Better maternal methionine is associated with better calf growth and health through to weaning. The maternal methionine supplementation appears to “prime” the fetus so the calf performs better after birth, and this suggests the up-regulation of certain metabolic pathways will ultimately improve the performance of that heifer when she becomes a cow.

Now that we know supplemental methionine has such a positive impact on the transition cow, the question now is: How do we supply the cow with supplemental methionine? The cow gets a basal level of methionine from rumen-undegradable protein (RUP) and microbial protein coming from the rumen, but adding supplemental methionine to the diet will be ineffective because free methionine, like choline, is rapidly degraded by rumen bacteria and will not contribute to the intestinal supply of methionine unless they are protected from ruminal degradation.

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Fortunately, there are a number of rumen-protected methionine products available to dairy producers. Most of these products rely upon some form of coating to protect the methionine until it reaches the intestine. The coatings can be chemical polymers or fat coatings or a combination. The amount of methionine they will deliver depends upon the quality of the particular protection technology. Alternatively, an analogue of methionine (methionine hydroxy analogue; MHA) or a derivative of MHA (HMBi) can be used as the MHA is slowly degraded in the rumen compared to methionine and is rapidly converted to methionine in the body. MHA has been used successfully for transition cows for over 20 years.

A big question, then, is how much methionine to feed. While methionine requirements are reasonably well defined for lactating cows, we don’t have a good understanding of what the requirements are for prepartum cows. Most recommended feeding rates are between 0.05% to 0.1% of DMI as intestinally available methionine (after accounting for how much methionine is delivered to the intestine in the specific product used).

Another complication is how we formulate these diets. For lactating cows, we build a diet for an “average” cow, assuming higher-producing cows will eat more and lower-producing cows will eat less. However, for prepartum cows, intake can vary considerably; cows that eat below average are most “at risk” for metabolic problems post-calving. Therefore, we should overformulate prepartum diets to contain about 20% more of our target methionine to ensure the “at risk” cows we are most concerned about get their appropriate nutrient level.

In summary, supplemental methionine is a highly effective and economical way to reduce metabolic diseases around parturition and increase milk production. It may also have a positive impact on the newborn calf and her subsequent performance.  end mark

Photo by Mike Dixon.

Lyle Rode is a ruminant technical services manager at Novus International. Email Lyle Rode.

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