In the approximately 15 years since the conversion of the U.S. milk pricing system to multiple component pricing, dairy farms have made tremendous progress in their production of milkfat and milk protein.
Where at one point in time, production of 6 pounds total of milkfat and protein per cow per day would have been considered excellent productivity, we now have herds shipping more than 7 pounds total of milkfat and protein per cow per day. Of this 7 pounds, more than 3 pounds is milk protein.
Figure 1 depicts the announced monthly Federal Milk Marketing Order prices for milkfat and milk protein from 2011 to 2015. In general, milk protein has a greater value than milkfat and during some months exceeded $4 per pound.
As an aside, the recent resurgence of demand for butter thankfully helped to maintain milk price during 2015. Nevertheless, over the longer term, production of milk protein is of major importance relative to meeting the global demands for dairy and contributes very significantly to the bottom line at the farm level.
Given that milk yield and milk protein yield are highly correlated, any management practice or strategy that increases milk yield will also increase milk protein yield.
Therefore, improvements in management in all facets of the dairy to include forage quality, transition cow management, grouping management and cow flow, nutritional management including both ration formulation and feeding management, reproduction, udder health, calf/heifer management and cow comfort will all contribute to increased milk and milk protein yield.
Furthermore, strategies such as 3X or 4X/2X milking and administration of rbST will directly increase yields of both milk and milk protein.
Although yields of milk protein are highly correlated with milk yield, the herds that will produce the most milk protein will do so from a combination of high milk yield and higher-than-average milk protein percentage. There are a number of nutritional factors to consider that may increase both milk protein content and yield.
Research conducted during the past several years continues to support the move away from crude protein as a way to evaluate protein supply to the cow and toward metabolizable protein systems in which mathematical models, such as the Cornell Net Carbohydrate and Protein System (CNCPS), predict both supply of microbial protein coming from the rumen as well as the supply of rumen-undegradable (bypass) protein.
Refinements in this model over time have enabled nutritionists to more tightly balance different protein fractions along with amino acids, thereby reducing the overall amount of purchased protein, increasing income over feed cost and at the same time decreasing nitrogen excretion into the environment.
In addition to balancing for metabolizable protein rather than crude protein, nutritionists can often drive milk protein content and yield by balancing both the methionine and lysine components of the ration.
Methionine and lysine have long been known to be first-limiting amino acids for production of milk and milk protein by dairy cattle, and supplementation with various sources of methionine to include both rumen-protected forms and analogs have been shown to increase yields of milk protein.
Lysine typically is high in rumen-protected forms, commercially available forms of soy that have been processed to increase their rumen undegradability and other protein sources such as blood meal and various animal protein blends available commercially.
Researchers at Ohio State and Cornell have illustrated that the digestibility of these animal protein sources can vary, and an assay developed at Cornell is being deployed currently at various commercial feed analysis laboratories to enable feed suppliers to evaluate the digestibility of their protein sources.
There are several ration formulation models widely utilized in the dairy industry in the U.S., and Table 1 lists several of these models along with the optimum ratios of methionine and lysine for milk protein production.
Differences between models are based in part on how they are constructed, but one trend that has occurred has been for increasing supplementation of methionine relative to lysine for production of milk protein.
One factor commonly overlooked in the discussion of nutritional strategies to increase milk protein production is energy. Protein synthesis in general is an energy-driven process.
Proof of concept research conducted in our laboratory several years ago using slow-release insulins suggested that milk protein could be increased when insulin concentrations would be comparatively higher, such as the case in a ration containing higher levels of fermentable carbohydrate.
Limited research conducted since that time has suggested higher supply of either propionate or starch, in combination with amino acid supplementation, may enhance the overall responses to amino acid balancing.
Of course, there are other factors beyond nutrition that can influence milk protein percentage and yield. In addition to the factors mentioned above relating to overall milk yield, facility and environment factors such as overstocking and heat stress can affect milk components by changing feeding patterns and affecting the rumen environment in various ways.
Furthermore, there is a strong seasonal effect on both milkfat and milk protein (see Figure 2 summarized by Clay Zimmerman from USDA-NASS statistics) in which both are highest in the winter, begin to decrease in the spring, bottom out in the summer and rebound in the fall.
Although Figure 2 represents Federal Milk Marketing Order 1 data, the same general pattern applies across the U.S.
In summary, high production of milk protein depends upon excellent execution of management strategies that increase milk yield as well as implementation of ration strategies using amino acid supplements that supply limiting amino acids to high-producing cows.
I speculate that overall responses to amino acids will be greatest in rations with higher overall carbohydrate fermentability and in herds with excellent feeding and facility management. PD
-
Thomas R. Overton
- Professor of Dairy Management
- Cornell University
- Email Thomas R. Overton
