How to test forages in cold weather

cattle grazing in snow
(Farm and Dairy file photo)

WOOSTER, Ohio — Colder weather means livestock need more energy to be able to withstand harsh winter conditions outdoors, according to a forages expert with Ohio State University’s College of Food, Agricultural, and Environmental Sciences.

And the best way forage producers can ensure they provide their animals adequate nutrients is to collect samples of forage and send it to a lab for testing, said Rory Lewandowski, an Ohio State University Extension agriculture and natural resources educator.

Cold temperatures, low wind chills, cold rain and muddy conditions can significantly increase the energy required by livestock metabolism to provide enough heat for the animal to maintain its body temperature, Lewandowski said.

And in the case of ruminant livestock, a major portion of the diet is typically composed of forages, he said.

“But all forages are not equal and forage quality book values are really not useful for on-farm ration balancing,” Lewandowski said.

“Producers have to realize that forages have a lot of variability, so if they really want to have the best idea of the nutrient value of their forages, they’ve got to get it tested.

“Testing forage samples is the only way to be able to match and adjust forage rations to livestock nutrient needs,” he continued. “Proper sampling will increase the accuracy and reliability of test results.”

Enough energy

Lewandowski said if conditions get too cold, it’s likely that some of producers’ hay crops won’t contain enough energy to meet the increased energy needs of the animal. At that point, he said, producers will have to supplement the animals’ feed.

Animals have a thermoneutral zone — a temperature range in which the animal is most comfortable, is not under any temperature stress, and which is considered optimum for body maintenance, health and animal performance.

But when livestock experience cold stress below the lower boundary of that zone, they reach lower critical temperature (LCT), and the animal’s metabolism must increase in order for it to keep warm, Lewandowski said.

“An increase in the metabolism of the animal in order to maintain body temperature, generally by shivering, is one method of how it deals with cold stress,” he said. “In order for the animal to do this, it requires more energy either from stored fat or more energy intake in the diet.

“Generally, energy intake must increase by 1 percent for each degree of cold below the LCT.”

Nutrient content

Forage nutrient content is affected by a number of factors, including maturity at harvest, species composition, moisture content at harvest, and handling of the forage during the harvest and storage period, Lewandowski said.

And in order to get the most accurate information on the quality of the forage sample, how the sample is gathered matters, he said.

“Proper sampling is very important because the potential for variability between samples is great,” Lewandowski said. “If the sampling isn’t done correctly, the test results will not be reliable.”

Tips to follow

To get a good forage sample for testing, producers can follow these tips:

• For dry hay, always use a forage probe to gather samples.

• Sample lots of hay separately. A lot of hay could be defined as hay of similar species content, harvested at a similar maturity and ideally from the same field and/or from fields harvested on the same day or within a couple of day span.

• First-cutting hay in particular can have large changes in forage quality within even a two or three-day span.

• For small square bales, sample at least 20 separate bales within a lot. Use the forage probe to sample from the end of the bale, between the twine.

• Medium and large square or rectangular bales have a more uniform distribution of leaves and stems compared to small square bales, so they can be sampled anywhere on the bale sides or ends.

• For large round bales, sample at least eight to 10 bales per lot of hay. Sample on the curved side of the bale, inserting the forage probe perpendicular to the side of the bale.

• When sampling ensiled forages such as haylage or corn silage, taking hand-grab samples from the face of the bunker silos is not recommended due to safety concerns. Use a loader bucket or face shaver to create a pile of silage on the floor of the bunker. If this forage is not going to be fed in a total mixed ration (TMR), then collect five to eight samples.
Combine samples into a 5-gallon pail, mix thoroughly and take a representative sample for analysis using a scoop.

• When sampling baleage or silage bags, hand samples can safely be taken from the face of haylage or corn silage in bags. Knock down or remove the amount that would normally be fed and collect four to five scoop samples.

Collect another four to five scoop samples from the newly exposed face and combine all the subsamples into a bucket, mix thoroughly and then collect a representative sample to send in for analysis.

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