World Grain - May 2023 - 41

this law. One of them being food that was intended for human
consumption. This is because of the extensive food safety
precautions set in place to certify a safe food supply for the
consumers as well as cooking and further processing. On the
other hand, there is no guarantee that food waste did not come
into contact with uncooked mammalian products. Additionally,
producers and feed mills may not want to take on the risk
for fear of disease or public opinion.
The other eminent concern is the variability in nutrient content.
A study conducted at Kansas State University wanted to
test the amount of variability by determining metabolizable
energy and amino acid digestibility trials with broilers (Beckman
et al., unpublished). Food waste nutrient availability was
determined by feeding weekly collections of food waste to
test if there were differences by time periods.
All food waste collections were mixed with soybean meal
and dry-extruded at a minimum of 284℃. This process created
a kill step for any bacterial concern while simultaneously
reducing moisture content to allow the food waste to be shelf
stable. Of the four time periods that were collected, they found
that the first week of food waste had a greater protein digestibility
of all amino acids than the second week. Additionally,
the third- and fourth-week food waste collections were intermediate
to the first and second weeks.
Lysine digestibility of the four week-long collection periods
ranged from 70.68% to 77.08% digestible while methionine
ranged from 67.42% to 76.48% digestible. Metabolizable energy
also was determined of the same four week-long collection
periods and ranged from 2,259 to 3,295 kcal/kg. The third
week had a greater metabolizable energy content than weeks
one and two with week four being intermediate. This shows
that variability may not be as much as initially thought and
that if enough food waste is composited together and monitored
for nutrient content, it could create a reliable feedstuff.
When comparing these thermally processed food waste products
to soybean meal, they had a similar protein digestibility
and energy content.
Previous research also has been conducted to determine the
value of different collection streams when fed to pigs. Pigs
fed food waste specifically sourced from a supermarket had
a greater methionine and tryptophan digestibility compared
to soybean meal while lysine digestibility was similar to soybean
meal (Fung et al., 2019). Recycling energy and nutrients
from various food waste sources into swine feeding programs
is constrained by the high variability and lack of data on the
digestibility of energy and nutrients. Therefore, the objectives
of this study were to evaluate the digestibility of energy,
amino acids, and phosphorus in thermally dried food waste
World-Grain.com / World Grain / May 2023
41

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World Grain - May 2023

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