Researchers at West Texas A&M university in the United States believe that crude glycerine, a byproduct of biodiesel production, could be an economical ingredient in livestock feed
In new research reported last week, AgriLife Research beef cattle nutritionist in Amarillo, Dr Jim MacDonald, explained that when biodiesel is produced from sources such as cottonseed oil, glycerol is separated from fatty acids.
The fatty acids become the biodiesel and the glycerol, combined with the impurities that remain, is a potential ingredient in livestock feed.
“Crude glycerin is usually priced at a discount relative to corn, so we wanted to look at replacing corn to evaluate at the energy value of the glycerin,” Dr MacDonald said.
Glycerin had good “flowability” in low temperatures, as opposed to molasses or other similar products, and was non-corrosive to feeding equipment — both traits that made it attractive to the cattle feeding industry.
Additionally, glycerin was low in phosphorus, protein and sulphur, which can be concentrated in other dietary ingredients.
While the researchers knew the physical and nutritional properties made crude glycerin an attractive carrier in liquid supplement programs, relatively little was known about its performance implications in growing or high-concentrate finishing diets for beef cattle.
For the past two years, Dr MacDonald has teamed up with Dr Mike Brown at West Texas A&M University to conduct four experiments designed to determine the value of feeding crude glycerin in beef growing and finishing diets.
The studies were designed to determine the feeding value, optimal concentration and which dietary components were most optimally displaced by crude glycerin in growing diets, he said.
Within the studies, the researchers looked at two strategies: replace corn or replace some forage. In the studies replacing corn, the researchers saw an optimal inclusion between 2.5 percent and 7.5 percent glycerin, Dr MacDonald said. At 10 percent inclusion, feed efficiency was reduced.
When forage was replaced in one study, they saw no change in average daily gain, but the cattle consumed less feed and so feed efficiency was improved, Dr Brown said.
The feed efficiency was improved when either 5pc or 10pc glycerin was fed. Another advantage was a less bulky ration as forage was replaced.
“I feel very comfortable using crude glycerin up to 7.5 percent of a diet,” Dr MacDonald said.
The researchers even tested for a possible negative impact on fibre digestibility, but found none when the crude glycerin was fed at the low levels.
“We also saw an increase in microbial protein and a reduction in rumen ammonia,” Dr MacDonald said.
This information could lead to further studies, he said.
In high-forage diets, often excess nitrogen is formed in the rumen, which is excreted as urea and volatilized into the atmosphere as ammonia. The crude glycerin may allow more of the nitrogen to be captured before it is excreted and, thus, reduce ammonia emissions of cattle grazing high quality forage.
“We also observed no negative impacts on animal health up to 10 percent inclusion in diets of newly received calves,”Dr MacDonald said.