Lying down on the job
Cows don’t ask for a lot. Ample high-quality fresh feed and water along with a comfortable resting place covers much of what they need. However, there’s new evidence that the fresh feed aspect, including particle length, is more complex.
During a recent Balchem Real Science presentation, Dr. Rick Grant, president at Miner Institute, discussed his favorite topic: precision chewing management.
“For the dairy cow, what could be more important to her in terms of precision chewing management than precisely meeting her needs for the big three behaviors: eating, resting and ruminating – particularly recumbent rumination?” Grant said. “All of those factors, when they are precisely managed, optimize health and productivity and are at the center of any successful dairy management program.”
If a dairy cow consumes feed and hits her dry matter intake (DMI) requirements for three to five hours per day, she will express natural, normal and healthy eating behavior. Recumbency (resting) and rumination are also critical – she should rest for 11 to 14 hours daily and ruminate for eight to nine hours daily.
“In the cow’s ideal environment, 80% to 90% or more of rumination should occur while she’s lying down,” Grant said. “Sternal recumbency promotes greater salivary secretion for each minute of rumination.”
Cows that achieve more rumination while lying down have healthier rumen pH conditions and a lower incidence of subacute rumen acidosis compared to cows that spend more than half their time standing with the same rumination time. While dairy cows experience little true sleep, rumination provides the physiological rest and rejuvenation that would result from sleep.
Part of the nutrition puzzle is whether the ration provides adequate physically effective (PE) fiber. With diets high in PE, cows spend more time eating but without increased rumination, resulting in less resting time.
Grant referred to recumbent rumination as the cow’s signature behavior. Cows with greater rumination while lying down have higher rumen pH, consume more dry matter and produce milk with greater fat and protein. The most efficient rumination takes place when the cow is sternally recumbent and lying slightly on her on her left side.
“It’s hard to increase rumination with longer particles because the cow is a leveler during the eating process,” Grant said. “We can depress rumination more finely than the cow. The bottom line is to process forages so the particle size is close to what the cow would create herself. The goal is not to minimize her eating time – it’s to get it to three to five hours per day.”
Forage maturity plays an important role in palatability and particle size. The chopper can be adjusted for the optimum particle size at harvest based on forage maturity. More mature forage should be chopped more finely. However, chopping forage too finely – finer than what the cow would naturally ruminate – can result in rapid passage and potential rumen health issues.
According to Grant, one of the goals in chopping forages is to mimic cows’ chewing. If the particle size isn’t adjusted during forage harvest or feed mixing to imitate the cow’s natural chewing behavior, her time at the bunk will be longer and take away from rumination time in a comfortable resting area.
Consider variations in maturity and moisture content at harvest and the differences between grasses and legumes. Mature forages and dry corn silage should be chopped more finely. The goal is chop length that ensures good packing in the silo to reduce dry matter losses and to optimize chewing behavior.
Particle size distribution is based on several factors relative to the forage and the chopper. Silage defacing, mixer knife sharpness, mixing time and other factors contribute to variations that ultimately result in sorting. If necessary, cows will spend the time at the feed bunk to reduce the particle size distribution in the ration.
“She makes it more uniform,” Grant said. “She tends to swallow boluses of feed when she’s eating to be relatively uniform in terms of particle distribution. Think about what’s going to happen before the ration particles actually get in the feed bunk. Once you get that fixed on the farm, you’re good to go until you sharpen the knives, then you might need to recalibrate.”
When the ration particle size is consistently too long, as is often the case with coarse, overmature forage, cows must spend more time chewing and will chew as long as necessary to reduce feed to the most desirable particle size.
“There are a couple components to precision chewing management,” Grant said. “Get the right forage to the right cows and manage starch to allow three to five hours per day eating time. Avoid excess eating time but stimulate recumbent rumination.”
According to Grant, cows that aren’t rushed while eating have the freedom to lie down and ruminate. Those provided with a balance between eating and recumbent rumination have optimal rumen conditions for fiber digestion, microbial growth and healthy production of milk and milk components.
If cows have the ideal diet relative to forage particle size but are crowded and can’t reach the bunker or lie down when they want to, they’ll have lower feed intake. Feed availability should be constant with feed push-up and managed competition.
Grant said the new science isn’t a done deal because many non-forage fiber sources are fed at different times of the year. Pastured cows on lush high-quality forage often consume a much longer particle length, but that may not be important because the cow might be able to fold it over and swallow it.
“For the first time, we are truly linking behavioral management with forage management,” Grant said. “We’re optimizing forage [particle size] and giving her an environment, forage and TMR designed to meet her needs from her perspective – the only perspective that matters. We are mimicking the cow relative to particle size reduction and putting her in an environment to ensure it’s the correct balance between eating and recumbent rumination.”
by Sally Colby
