by Katie Raver, MS, PAS, Dairy Technical Services Manager
As cheese prices have risen over the past year, more attention has been paid to finding ways to increase milk protein production on the farm. According to the Milk Pay website with today’s market, each additional 0.1 unit of protein produced is valued at $0.27/hd/day. Per year this equates to about $100 per head. This is can have a substantial economic impact on herds of any size. So, what can be done to improve milk protein percentage and yield to improve the bottom line?
Although the number of components produced is a relatively highly heritable trait, diet does have an impact as well. We often focus on altering milk fat percentage and yield research has shown that diet can also impact milk protein production. It is estimated that dietary changes can account for a 0.6 unit difference in milk protein production.
To better understand what dietary changes can be made to help improve milk protein percentage, it is important to understand the origin of milk protein. Milk protein is synthesized from amino acids, some of which are capable of being synthesized in adequate amounts by the cow and some of which must be supplemented in the ration. Amino acids are supplied through three main sources: microbial protein, rumen undegradable protein, and endogenous protein. Because ruminants derive a considerable amount of protein needs from ruminal microbial protein flow, the amount of ammonia and AA required for microbial protein synthesis as well as AA requirements of the cow should all be taken into consideration to maximize the efficiency of protein utilization.
A large driver of both milk protein yield and milk protein percentage is dry matter intake as a result of higher energy intake. This increase in dry matter intake will also likely lead to an increase in total grams of metabolizable protein consumed from both rumen degradable and rumen undegradable sources. This increase in MP will increase the number of precursors needed for milk protein synthesis.
Microbial protein is a very high-quality source of amino acids and can be efficiently used by the cow to synthesize milk protein. Inadequate amounts of rumen degradable protein can limit the amount of microbial production. Lower than desired MUN levels may be an indication that rumen degradable protein is in short supply and this can limit milk protein and milk yield. One strategy to increase microbial protein yield is increasing RDP through feeding urea. Diets that are high in highly fermentable NSC often can benefit greatly from feeding a rapidly utilized protein source such as urea. This helps create a protein and energy synchrony in where carbohydrates and proteins are utilized at similar rates maximizing the efficiency of use and microbial population. QLF liquid supplements are an excellent way to carry urea as they increase distribution, palatability, and provide rapidly fermentable carbohydrates in the same package. In addition, a meta-analysis done by de Ondarza et al found that in two data sets supplementing a high quality sugar source tended to increase milk protein yield up to 0.15 lbs/hd. In the study, the increase was hypothesized to be caused by an increase in microbial protein production.
As the average milk production increased across the US the ability of microbial protein and bypass protein to supply all AA decreased and amino acids became limiting in milk yield and milk protein production. With this in mind, a correct balance of methionine and lysine can also help to maximize milk protein yields. Feeds such as blood meal are often high in lysine while feeds derived from cereal grains can be a good source of methionine. However, when not supplied by the ration, feeding a bypass amino acid source can be an economical way to provide the needed AA for maximum milk protein production. Studies have shown that supplementing rumen protected methionine to achieve an ideal lysine: methionine ratio (3:1- 2.7:1) resulted in improved milk protein content(+0.15%) and total yield (+0.26lbs). Other research has found that supplementation can even result in improved health and immune status. Lysine is a very common AA found in milk therefore it can become limiting to milk protein production. Feeding a rumen protected lysine source can also have positive impacts. A 2019 study found feeding RP lysine and RP methionine increased milk protein percent by 0.12%, in addition it also decreased SCC. Some strategies for feeding AA include decreasing total protein content while closely balancing AA to help maximize milk protein while keeping ration costs manageable.
There are ways to positively impact milk protein production, and if implemented correctly this can help increase profitability. As always, the whole ration must be taken into account when making dietary changes. It is important to consider not only the cost of a product but the return on investment when making decisions.
de Ondarza, M.B., S.M. Emanuele, C.J. Sniffen. 2017. Effect of increased dietary sugar on dairy cow performance as influenced by diet nutrient components and level of milk production. Appl. Anim. Sci.
Osario, J.S., P. Ji, J. K. Drackley , D. Luchini , and J.J.Loor. 2013. Supplemental Smartamine M or MetaSmart during the transition period benefits postpartal cow performance and blood neutrophil function. J.Dairy Sci.
Lee, C., N.E. Lobos, W.P Weiss. 2019. Effects of supplementing rumen protected lysine and methionine during prepartum and postpartum periods on performance of dairy cows. J. Dairy Sci.