FAYETTEVILLE, Ark. — Calcium is a crucial mineral in the overall health for living things. A healthy portion in your diet leads to strong bones and teeth, but, in poultry, it means so much more.
In poultry production, it’s important to give birds the right amount of feed so that they produce the desired number of eggs and meat, grow healthily, and have low disease risks. To do that, there must be the right balance of multiple ingredients, especially calcium.
“With calcium, there’s a lot of different functions in the body, but the main driver of the amount of calcium a bird needs, if we’re talking about broiler chickens, is for bone synthesis and formation,” Ben Parsons, assistant professor of poultry nutrition and poultry science at the University of Arkansas, said. “If you’re talking about laying hens, it’s going to be for eggshell synthesis and production, once they enter that period of their production stage.”
In addition to accounting for the benefits of calcium in the diet, producers and scientists must think about the consequences of calcium in the diet.
“It has been found…that with certain calcium sources, we’ve seen some evidence of performance issues in broilers, some more so in laying hens,” Parsons said. “If we’re having performance issues, that’s obviously going to cost us a lot of money.
“Our three most expensive components in the diet, from a nutritional standpoint, are energy, amino acids, and phosphorus,” Parsons added. “Calcium will actually reduce the availability of phosphorus … an expensive nutrient in the diet.”
While most would think that too much calcium is better than too little calcium, it turns out that it can be an entirely different issue.
“There’s some work that has come out of Texas A&M with Dr. [Audrey P.] McElroy there showing that excess calcium actually can make some of our disease challenges worse in the diet,” Parsons noted.
Despite all the pros and cons of calcium in the poultry diet, what is vitally needed for the birds is how much can be used and absorbed, in essence, the nutrient’s bioavailability. Parsons and other poultry scientists are working towards more precise availability estimates of calcium, in a way different from their current approach.
“Right now, we just formulate to meet a total calcium requirement,” Parsons said. “But what that’s doing is it’s not accounting for differences among feedstuffs in terms of how available that calcium is or even differences among the same ingredient.”
Comparing tests
As you can see, calcium and measuring calcium availability are complicated parts of the poultry diet. That is why poultry scientists are working hard to find the best way to assess the availability of calcium in the poultry diet. Parsons and his colleagues recently published a study comparing the leading calcium availability tests.
“We have two main approaches that we’re looking at for assessing availability of calcium and our different ingredients,” Parsons said. “So, what the study was getting at was trying to better understand these different approaches that we have so we can start to more widely use them for evaluating sources, because we’ve got to have the approach refined in order to start actually looking at a lot of different ingredients.”
One of the tests is a new, quicker approach called the “ileal digestibility test.”
“It’s very rapid. We only feed the diets for about 24 to 72 hours, so one to three days, and then we go in and collect digesta from the [gastrointestinal] tract,” Parsons noted. “It’s a quantitative measurement, so you measure how much calcium was in the feed that the birds ate, how much was left at the end of the GI tract, and the difference between those values tells you quantitatively how much the bird was able to absorb.”
Although the new test is quicker and straightforward, Parsons and his team found one problem with it, causing them to look deeper into the older approach.
“We’ve seen a lot of different factors within … how the study is run that affect the digestibility value,” Parsons said. “So, we’ve also been working on kind of modifying a very classical approach, which is the bioavailability assay, where we use actual bone growth as kind of an indicator of how available the calcium is.”
Aside from the difference in time, where the new approach takes no more than three days and the classic approach takes two weeks, the other difference in the tests is what it tells you about the calcium. The ileal digestibility test only accounts for absorption, while the bone ash test accounts for absorption, transport, and usage within the body.
Parsons and his colleagues found that each test yields the same results, which is a good thing from a research standpoint.
“What we hope for is [that] … we find the same results using two different approaches [because] that tells you that you’ve got something real when you can repeat it using two completely different methods,” Parsons said. “So, the goal was to really better establish these tools, so that we can move forward and start implementing these and evaluating a lot of different feed ingredients.”
Future research
Parsons is already thinking about the impact of this study moving forward and what goals can be achieved in the realm of calcium digestibility.
“The longer-term goal would be eventually to start formulating on a digestible or available calcium basis like we do for amino acids and energy and phosphorus,” Parsons added. “That takes a lot of time to really build up a good database of values.”
As for short-term goals, he is hoping that they can start using these approaches to help other departments figure out whether any problems they are facing in the field are calcium related. Parsons and his colleagues also published their study in the Poultry Science journal under the title “Comparison of relative calcium bioavailability based on bone ash and apparent ileal Ca digestibility in broiler chickens.”
