IFM lab characterizes four U.S. dairy diet profiles

In vitro fermentation model suggests regional strategies for total mixed rations for dairy cattle.

Since 2013, more than 1,500 feed samples have been analyzed at Alltech’s In Vitro Fermentation Model (IFM) laboratory in Brookings, S.D., and with those data, researchers have been able to put together four specific regional dairy diet profiles.

IFM is a practical diagnostic tool used to evaluate and troubleshoot total mixed rations (TMRs) to achieve optimal rumen fermentation and feed utilization, Alltech said. Utilizing IFM technology, feed samples are incubated within a standardized rumen fluid and a buffer system to mimic natural rumen fermentation in an oxygen-free environment. IFM then measures gas production, identifies TMR inefficiencies and provides additional information on the nutritive value of the feed.

“The main feature of IFM is the ability to estimate the contribution of the different carbohydrate pools: a fast pool representing soluble carbohydrates — starches and sugars — and a slow pool representing available fiber,” said Dr. Kamal Mjoun, research scientist at the Alltech IFM lab in Brookings. “The balance and the specific rate of fermentation of these pools are crucial to the efficiency of the fermentation and the utilization of the feed by the animal.”

Most samples submitted to the lab originated from the Midwest, with 45% of total samples analyzed, followed by the Southeast, Northeast and West/Southwest, with 25%, 18% and 13% analyzed, respectively. Regional differences in feeding systems, available feedstuffs and their nutritional quality were reflected in the chemical composition and rumen fermentation profiles of the samples.

Alltech said these differences include:

* Feeds from the Southeast and West/Southwest had more fiber and less starch than feeds from the Midwest and Northeast, likely because of higher forage and/or byproduct inclusion rates.

* Lignin and total sugars were highest in feeds from the West/Southwest and comparable in those from other regions.

* Crude protein was higher in Midwest and West/Southwest samples than in Northeast and Southeast samples.

* In terms of fermentation parameters, feeds from the West/Southwest region had the highest amount and percentage of the fast pool, and feeds from the Northeast states had the lowest, likely because of feeding high levels of corn silage and byproduct feedstuffs.

* Fiber quality, indicated by the size of the slow pool and its rate of fermentation, suggests that samples from the Midwest and Northeast had the best-quality forages, followed by the Southeast and, finally, West/Southwest.

Overall, researchers determined that the nutritional value of TMR, measured as in vitro dry matter digestibility, is highest for Midwest samples, followed by the Northeast, West/Southwest and Southeast (81-78%). Milk production from these samples ranged from 83.0 lb. to 75.4 lb. for TMRs from the Midwest to the Southeast, Alltech said.

“These results can be used to suggest specific supplementation strategies to optimize the fermentation profiles of a TMR and maximize feed efficiency and dairy performance,” Mjoun said.

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