A team of researchers from Indiana-based Purdue University examined the susceptibility of feeds made with dried distiller’s grains with solubles (DDGS) to insect infestation by Tribolium castaneum - the red flour beetle. The group published its work in the Journal of Stored Products Research.
The group found that feed particle size corresponded to insect growth and development.
Masha Fardisi, postdoctoral research associate in the department of entomology at Purdue University and corresponding author, said there is a continued need to protect food and feed sources from insects both before and after harvest.
“Dried distillers grains with solubles (DDGS) is a co-product of the grain (mostly corn in the US) ethanol production process plants and due to its high nutritional value it has been used in animal feed. We wanted to see how fast insects would grow on DDGS.”
Additionally, as the international market for DDGS has expanded, the feed ingredient has remained competitively priced compared with corn, she told us. Known susceptibility to insects could damage prices.
“Potential insect contamination in the DDGS export may negatively affect DDGS US market international demand and costs to export due to requirement of fumigation for insects if contaminated,” she said.
In its work with DDGS, the group looked at the red flour beetle because it is an important insect pest found in stored products, she said. It is often present in traps set to monitor insect presence in storage facilities, she said.
When a feed is found to be susceptible to infestation, it increases the possibility that stored feed will be infested, said Fardisi. “T. castaneum or any other insect infestation reduces food/feed quality and quantity,” she added.
“They do this by reducing the product weight through ingestion of the seed, contamination by fecal matter and dead insect bodies, creating an environment that promotes the growth of molds and mycotoxins, and by increasing the potential for driving the product over the Defect Action Level of the FDA,” she said.
The beetle also has been linked, in earlier research, to the presence of pathogenic bacteria in animal feed. The adult version of the insect is known produce harmful quinines.
Study: Methods and materials
In the study, the researchers examined the ability of several different feeds to host the insect pest. The commercially available feeds tested included a crumbled poultry feed, a pelletized juvenile frog feed and a pelletized adult feed frog feed.
The poultry feed included 10% DDGS, and the frog feeds had 5% DDGS inclusion amounts, the researchers said. A portion of poultry feed was ground to specifically examine the role particle size played on insect development.
The researchers also made six flour and yeast based feeds with increasing amounts of DDGS present at 0, 10, 20, 30, 40 and 80%, they said.
The pelletized adult frog feed had the largest particle sizes, the researchers said. The ground poultry feed and the lab-made feeds offered the smallest particles.
Insect eggs were added to containers of the different feeds and checked from day 3 every six hours until larval emergence, they said. Samples were then assessed daily through pupation or insect mortality.
Results and looking forward
Overall, the results from the insect production suggested particle size of the feed has more to do with susceptibility for insect infestation than the presence of DDGS alone, said Fardisi.
Insect development and mortality was altered by the different diets, the researchers said. Growth periods were 1.4 times longer for crumbled feeds and 1.8 times longer for the larger of the pelletized feeds.
Rates for insect growth in the ground poultry feed and lab-made feeds were similar, they said. However, larval mortality was highest for insects on the crumbled poultry feed and similar for all other feeds.
“Our results suggested that particle size was one of the influential factors on susceptibility of DDGS as a raw ingredient and feed containing DDGS in their formula mixture to T. castaneum irrespective of feed chemical composition,” said Fardisi. “We also found out that T. castaneum development elongated at [the] lower humidity of 30% on DDGS than either feeding on their normal laboratory diet or on DDGS at a higher relative humidity of 50%.”
The take away for those storing raw DDGS would be to reduce the humidity of the product, or when processing it to pelletize it, she said. “We also recommend that plant managers monitor for insect infestation not only by using traps but also personal observation and sampling commodities,” she added.
“[An] empty trap catch does not necessary mean that there is no or low insect infestation,” said Fardisi. “If the unnoticeable [or] low insect infested commodity moves from low to high humidity environment, insect development hastens and they can establish a significant population in a short period of time, reducing food/feed quality and quantity.”
Looking forward there would be several questions remaining regarding the susceptibility of DDGS to infestation by other feed pests, she said.
Source: Journal of Stored Products Research
Title: The susceptibility of animal feed containing Dried Distiller's Grains with Solubles to Tribolium castaneum (Herbst) infestation
Authors: M. Fardisi, L. Mason, K. Ileleji,