The US Department of Agriculture’s (USDA) Agriculture Research Service (ARS) announced the release of two new varieties of barley with larger amounts of bioavailable phosphorus and reduced phytate earlier this month. Of the two varieties, Sawtooth is a hulless barley while the Harriman variety is hulled.
Work on breeding these specific lines of barley started several years ago said Phil Bregitzer, plant geneticist with ARS Small Grains and Potato Germplasm Research Unit in Aberdeen, Idaho. “It’s just a continual process of improvement,” he added.
“The rationale behind working on these mutants is that most phosphorus is stored as phytic acid and it can be broken down by ruminants, but other animals and humans can’t digest it,” he told FeedNavigator.
If the phosphorus in a feed is not bioavailable to the animal then producers have either to supplement feed with additional phosphorus or add phytase enzymes to degrade the phytate, he added.
“The idea behind the cultivars is that you could have something that led to better animal nutrition, health and growth – and you wouldn’t have to add enzymes to feed,” he added.
Reduction of phytate and feed
In non-ruminant animals phytic acid can bind to iron and zinc and contribute to iron and zinc deficiency, said Victor Raboy, plant geneticist with ARS’ Small Grains and Potato Germplasm Research Unit.
“However you approach formulating animal feeds, whether it’s adding phosphorus or phytase that costs money, a person can calculate the cost of supplementing feeds to deal with the phytic acid issue,” he said. “If we have a plant breeding approach to solve the problem – that added value is in the feed you don’t have spend the money on phosphorus or phytase, and that value is a lot.”
The work with phytate also has been examined in other feed crops like corn and soybeans, he said. And the genes involved are the same in some other feed crops.
“You can use the knowledge for various approaches to manipulate that gene in any species – that work is relevant to corn [and] rice,” he said. “Both the genetic knowledge and the technology can be used in other crops.”
In addition to reducing the need for either supplemental phosphorus or an enzyme, the use of a low-phytate barley in feed for non-ruminants may help limit the extra phosphorus excreted into the environment, said Bregitzer. “Any phosphorus that is passed through the animal ends up in the water,” he added.
Once mutant lines of the barley varieties with lower phytate levels were established work was done to improve other aspects of the plant to make them viable for commercial production, said Bregitzer. Part of that effort included moving the low-phytate trait from strains of barley commonly used for malting to one with better yields.
“If all you’re doing is barley for feed then there are a lot less restrictions,” he said. Feed barley can be bred for agronomic performance rather than malting quality and performance, he added.
One objective of the breeding project was to take the genes related to the low phytate trait and move them to a high-yield feed cultivar from strains designed for malting, he said.
The mutation can be associated with side effects like reduced yield and less plump seeds, he said. Sometimes the side effects are unavoidable, but in other instances, the trait can be maintained after the side effects are mitigated through additional breeding.
“What we’d hoped to do was to take the raw mutants, put them in feed barley and do a series of crosses, and using best progeny to make the best crosses and put that low phytate gene into a background,” said Bregitzer. “So you could bring up the yield and have plumper grain.”
At this point, the new varieties are competitive with other feed barley varieties, he said.
As more producers have started using enzymes in feed to degrade phytate and focused more on corn use, there are some questions about where the new varieties will fit, he said. “But we had made progress, we had two varieties that were significantly better than the previously released varieties and we wanted to have them out there as varieties,” he added.
However, the production method used to generate the initial mutants and the process of cross breeding means the barley varieties are not considered to be genetically engineered, he said. “Technically these aren’t GMO,” he added.
“If you’re growing organically and are interested in environmental sustainability then this would be attractive – to give your pigs better nutrition and [a feed] that would result in less phosphorus in their manure,” said Bregitzer.