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Getting it right: Balancing partial mixed rations

Matt Leak for Progressive Dairyman Published on 17 April 2019
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Successfully implementing a robotic milking system starts with a clear understanding of the impact and demand on the nutrition program. While robotic systems can be the solution to many challenges on the dairy, they are not without challenges of their own.

Having an upfront understanding of these new obstacles, and planning for them in advance, can set you up for success before diving in.

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I’ve been balancing rations for robotic milking herds for more than five years, and one of the biggest challenges is getting the amount of dry matter (DM) intake correct. We now have to account for what the cows will eat in the partial mixed ration (PMR) and at the robot, while recognizing that each cow will consume a different amount at the robot as it correlates to her milk production in real time. If we are not feeding cows correctly at the bunk, they are not going to be healthy, or milking enough to visit the robot. 

In a free-flow robot system, there is a direct correlation between number of visits to the robot and the amount of milk a cow produces. I see fresh cows milking five to six times at the robot, and it has really driven an increase in production. In a traditional system, they would have only been milked two or three times, and it would have limited their production. This is one of the reasons it’s crucial we get the PMR as precise as possible.

In addition to balancing the DM intake, we also have to balance the forage-to-concentrate ratio of the PMR in conjunction with what each cow is getting at the robot. This is where it can really get tricky because we’re accustomed to a traditional TMR where grain is provided at the same rate as forage.

In a traditional herd, a cow making 100 pounds of milk might be eating 60 pounds of DM intake from the TMR. However, in a robot herd, a cow making 100 pounds of milk might be eating 40 pounds of DM from the PMR and 20 pounds of DM at the robot. Each cow can consume a different amount each day at the robot based on her milk production, so the DM intake can be more variable than when feeding a traditional TMR. If we don’t have the forage-to-concentrate ratio right, we’re putting ourselves at risk for serious trouble with acidosis. 

Due to the challenges of balancing the DM and forage-to-concentrate ratio in the PMR and the robot feed, I have to do rations manually by building special spreadsheets and can’t just rely on a ration formulation software to balance it for me. For my robotic milking herds, I balance diets for average cows, in addition to really high and low cows, then extrapolate out what’s needed for the robot feeding table at various ranges of milk production. Having enough time to work on these diets is essential, so I advise dairy farmers to discuss the transition to robots with their nutritionists early in the exploration phase.

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Even if we have everything balanced correctly on paper, if we get into low-quality forage, things can quickly go sideways, more so than a traditional herd. When cows on a regular TMR get into bad forage, they stop eating altogether, but in a robot herd, they have the option to stop eating at one place, such as the PMR, and continue to consume feed at the robot. This can increase the risk of acidosis, especially the subclinical form. When subclinical acidosis is going on in the background, it can impact DM intake and reduce butterfat. The best way to manage this increased risk is to closely monitor PMR intake and forage quality. 

I can’t stress enough the importance of high-quality forage. The best way to avoid cows going off feed is to avoid feeding bad forage at all. If a dairy is going to spend money on robots and expect extra milk, they have to be putting time and investment into producing high-quality forage, or they will never be able to fully benefit from the robot system. 

For this reason, I would advise any dairy considering robots to be sure the volatile fatty acid profile of their ensiled forages is consistently where it needs to be before they ever consider investing in a robotic milking system. Once they get this piece right, then they will be ready to look at robotic milking systems, and they will be more likely to reap the full value from the investment.  

Finally, one last element to keep in mind when you transition from feeding TMR to a PMR is the logistical setup of the storage area. While you might have the space you need for all of the ingredients in the PMR, you might not have the additional space for the robot feed. If you are feeding a pellet at the robot, consider how often you will need to fill the bin with pellets, how often the feed company will be able to deliver pellets to your location and how much of a supply cushion you want when unpredictable situations arise, such as snow storms. This is a lesson that has been learned through experience and one of the few things my robot customers would change if doing it over again. 

While formulating and balancing rations for robot herds can be more challenging than traditional TMR, working with a nutritionist early to discuss feeding strategy is the place to start. If you make sure forage quality is where it needs to be and understand the additional storage capacity and logistics for robot feed, your dairy can successfully implement this exciting technology.  end mark

PHOTO: Work with a nutritionist early to discuss feeding strategies before switching to robots. Photo courtesy of Cargill Animal Nutrition.

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Tim Clark
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