That perfectly balanced ration, carefully curated by your nutritionist, looks ideal on paper -- or, more likely, in your feeding software.
But how often does the prescribed formulation actually make it to your cows? When it doesn’t, why not? And what is the fallout? A team of researchers from the University of Nebraska looked at the disparity in dairy rations between formulation and feed-out, and examined the causes of inconsistencies.
Their study, published recently in the Journal of Dairy Science, examined the feeding records of 8 commercial dairy farms over 52 weeks, from November 2019 to November 2020. They used OneTrack Dashboard, a software program that calculates deviation in chemical composition of a total mixed ration (TMR) compared with the formulated ration.
The research team, led by Addison Carroll, sought to not only identify the variation, but to assess its impact on the herd production factors of milk production and pregnancy rate.
One of their most interesting and surprising findings: overfeeding, and a lot of it. When the data was broken out in 28-day segments, they found that measurable inconsistencies happened an average of 92% of the time every 28 days. In most cases, those inconsistencies represented overfeeding, not underfeeding, of nutrients.
All of the nutrients analyzed – crude protein, fat, neutral detergent fiber (NDF), and starch – were overfed at extremely similar frequency. The herd-level implications of ration deviation included:
- Overfeeding of starch resulted in reduced dry-matter intake (DMI). This did not surprise the researchers, because when starch ferments in the rumen, it supplies more available energy which leads to decreased meal size. Excess starch also my lower rumen pH and cause mild acidosis, which also suppresses DMI.
- Feeding extra crude protein increased DMI, which is consistent with previous research.
- Milk yield and energy-corrected milk increased when starch was overfed, but decreased when NDF was overfed.
- Feed conversion ratio increased with when excess starch was fed, but decreased when fat was overfed.
- Pregnancy rate increased when excess fat was fed, but decreased when crude protein was overfed.
The Nebraska researchers noted, “We recognize that the calculated nutrient deviation of an overall TMR is an oversimplification because individual feedstuffs such as corn silage have dally variation in nutrient composition.”
They also said interactions between weighing accuracy, nutrient composition, and physical form of various feedstuffs likely exist and may play a role in the ration variation they observed.
Some farms in the study were found to have miniscule variation between their prescribed and actual rations, while others showed very significant swings between the two.
To prepare and deliver TMRs more accurately, the researchers suggested the potential to utilize targeted alerts within feeding systems to improve feed management. More research pinpointing the parity and lactation stage at which cows were most sensitive to nutrient deviation also could be helpful in guiding feed management decisions.
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