Cells lining the inside of your digestive tract are on guard 24-7 letting nutrients into the bloodstream and blocking harmful substances from entering the bloodstream. It’s no different in cattle.
Barrier function of the bovine intestinal tract is the subject of new research in progress at the University of Saskatchewan where master’s candidate Rae-Leigh Pederzolli will be analyzing the potential of an altered feeding strategy with a novel supplement added to the ration to reinforce barrier function during times of stress.
The novel supplement will be a cocktail of several compounds that may help minimize tissue damage and promote tissue growth in the digestive tract so that calves resume normal feed intake without digestive upsets following a disruption in the diet.
“The main situations in the beef industry that hinder performance are new cattle at feedlots and cattle going off feed once they’ve been adapted,” Pederzolli says.
A general practice at feedlots after inclement weather that delays feeding operations is to go to a storm diet by backing off grain a couple of steps and replacing it with forage for a short time before stepping up the grain content again, she explains.
Likewise, the two storm diets, one with the cocktail and one without, in her study will include a higher percentage of forage than the baseline finishing ration, but both will be fed for a full week following five days of low feed intake. Another group will immediately return to the high-grain finishing ration, which is expected to cause acidosis. The control group will remain on the finishing ration without interruption.
If the cocktail storm diet proves to be effective, this strategy could be useful following other times when feed intake is reduced, such as weaning and transport.
Preconditioning on the ranch has long been suggested as a way to ease transition to the feedlot, but it comes at a cost to cow-calf producers, often with little reward from the marketplace, so there’s not much incentive to do it if they’re not retaining the calves, she adds.
The hope is that managing the feed program following a disruption, by including a high percentage of forage, a cocktail supplement, and a week-long recovery period, will improve health and production without the use of antimicrobials, thereby reducing cost and the chance of antimicrobial resistance developing.
This study builds on background from her initial trial that looked at permeability of the gastrointestinal tract (rumen, omasum, duodenum, jejunum, ileum cecum and proximal and distal colon) under two typical scenarios, ruminal acidosis and low feed intake, compared to a control group.
The baseline diet was a backgrounding ration, half forage and half concentrate. Ruminal acidosis was induced by restricting dry-matter intake to 25 per cent of the steers’ voluntary feed intake for one day, followed by one day of feeding pelleted barley grain to make up 30 per cent of daily dry-matter intake. Rumen boluses with pH probes confirmed acidosis with an average pH of 5.86 compared to an average pH of 6.55 for the control group.
The low-feed-intake challenge was five days of restricting daily dry-matter intake to 25 per cent of body weight. Average rumen pH was 6.94 over the five days.
The steers were killed immediately following the challenges and samples were gathered from each region of the gastrointestinal tract. Permeability was tested with the use of a Ussing chamber, which measures how molecules cross tissue. Inulin (large-size molecules) and mannitol (small-size molecules) were used in this study.
There were no differences among the control, acidosis and low-feed-intake groups for inulin flux across any of the tissues.
The distal colon was the only part of the digestive tract with altered permeability and that was for mannitol in response to restricted feed intake.
Short-duration ruminal acidosis didn’t affect permeability of any part of the digestive tract, although Pederzolli doesn’t doubt that sustained ruminal acidosis could lead to ulceration and potential perforation of the lining. When this happens, bacteria from the digestive tract could leak into the bloodstream causing a systemic infection that damages the liver and potentially the hooves.
The new trial will again evaluate differences in permeability of tissues from certain regions of the gastrointestinal tract and a concentration gradient applied in the Ussing chamber will shed more light on fluctuations over time.
She will also be looking at short-chain fatty acid absorption. Short-chain fatty acids include acetate, propionate and butyrate metabolized from feed and released fairly quickly into the bloodstream to provide energy.
“Tissue permeability is just one piece of the barrier function puzzle that also includes roles such as mucous secretion and supporting microbial communities,” she explains. “There has been a lot of research on the rumen, yet a decent amount of fermentation takes place in the hindgut (cecum and colon) as well and very little research has looked at how hindgut tissues respond when challenged.”