The balancing of amino acid (AA) levels in dairy rations has been in the news, useful commercial products have been introduced and formulation software has been updated. What are realistic expectations today for AA balancing? The answer rests with research results, what is measured on-farm and transition considerations.

Luchini daniel
Daniel Luchini

The vast majority of research regarding AA effects in peer-reviewed journals relates to milk volume and composition. Most of these university research trials were conducted with cows from early to mid-lactation. In a sense, conducting research trials with cows in this phase of production is expected. The cows are at peak production. Because the research objective was to show improvement in the cow’s milk production and composition, conducting the research during early to mid-lactation is ideal.

Over the years, the results clearly demonstrated that the cow’s milk production, composition and nitrogen utilization can be improved greatly by balancing the AA of the diets. Besides having a big impact on milk composition and often increased milk volume, the underlying impact is on improving the efficiency of how the cow utilizes the ration’s protein while reducing the ration’s crude protein.

Methionine and lysine are the most limiting AA in North America, and several commercial, rumen-protected products are available for use in enriching the cow’s diets with these two AA. The use of these products is often justified based on an expected, combined response in milk protein, fat and volume.

The main reason is because producers can detect these effects fairly quickly and easily by checking the milk tank. However, focusing solely on milk production and or composition is shortsighted. The cow’s response to a diet well-balanced for AA goes beyond milk production.

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Longer-term response

It is ironic that, in order to justify the inclusion of AAs in the diet, nutritionists rely on extra milk production. When producers are asked about their experience after balancing the AA of the diets, their response often is about the cow’s improved health and reproduction. Because detecting these effects in the herd takes longer than seeing a response in milk production, however, volume is the first and usually only valued response.

Immediately after calving, cows are at the highest risk of suffering a disease – a high incidence of diseases during this period impacts performance during the rest of the lactation and often impacts the cow’s ability to reproduce normally. In order to detect significant improvements on health or reproduction, detailed information on a large number of cows going through their lactation cycle is needed.

Because time is of the essence in appreciating the impact of nutritional management, it is hard to find published research trials geared to show the impact of feeding a balanced diet on health and reproduction. Therefore, nutritionists seldom promote better herd health and reproduction to justify the use of an AA-balanced diet to improve the bottom line.

Normal weight loss

In The Merchant of Venice , Shylock demanded one pound of flesh from Antonio, the merchant, to pay for the money he borrowed. We may judge it as excessive and cruel, but, this is what we routinely expect cows to do every time they start a new lactation cycle. It is normal for cows to lose more than 100 pounds of “flesh” immediately after calving.

After calving, cows have a high demand for nutrients and cannot consume enough feed to keep up with their milk production. As a result they lose a great deal of bodyweight. Bodyweight loss after calving is normal; in fact, it is accepted that cows will lose between 0.5 and 1 points of body condition score (BCS) within the first quarter of the lactation cycle every year.

Imagine yourself losing 10 percent of your weight – to gain it back within a year’s time. Would you be able to withstand such a challenge? We are not Shylock but we can be if we do not offer cows the right nutrition during the critical transition time period.

Impact at transition

Balancing the AA of the transition cow diets is of utmost importance. Year after year, we expect more milk and breed cows with the objective that their progeny will have the genetic makeup to produce more milk. In order to exploit the genetic potential of these cows and yet keep them healthy, we need to provide the right nutrients to meet their demands, including their AA needs.

AA are required nutrients, the building blocks of protein in the body and milk. Some AAs, such as methionine, also have an important role in metabolic functions beyond making milk or body protein. Methionine has a role in reducing the incidence of fatty liver during the transition phase – its deficiency in early lactation can negatively impact the whole lactation cycle.

Recently a study at the University of Illinois evaluated the impact of feeding a methionine-enriched diet from 21 days before calving to 28 days in milk. The results were reported at the annual meeting of the Dairy and Animal Sciences Association in 2011 and 2012.

In order to show the effects of added methionine, one group of cows was fed a basal diet deficient in methionine and two groups were fed the same basal diet with two different methionine sources, with the goal of matching the diet’s lysine content. The cows fed the methionine-enriched diets averaged an extra five lbs of milk. Most importantly, these cows had a significantly higher dry matter intake after calving which resulted in a lower liver fat accumulation.

The authors also reported that more cows fed the methionine- deficient diet had to be pulled out of the trial due to a higher incidence of diseases. Furthermore, the methionine-fed cows had lower BCS, but were healthier. The extra methionine in the diet did not prevent the cows from losing weight immediately after calving.

However, a better AA balance induced higher milk production and lowered their liver fat accumulation. The Merchant of Venice’s ending would have been different had it been written based on the results of cows receiving methionine-enriched diets during the transition phase. PD

Luchini is the manager of ruminant product technical services for Adisseo, has a Ph.D. in Dairy Science from the University of Wisconsin and has received seven U.S. patents.

Dan Luchini Ph.D.