Long-Term Storage of a Natural-Ingredient Diet within Variable Conditions of Temperature and Humidity
Institutions with aging structures may face difficulties maintaining consistent temperature and humidity for feed storage due to continued daily use of older heating, ventilation, and air conditioning systems and maintenance of structural integrity since the environmental efficiency of buildings often reduces as structures age. Consequently, institutions can face difficult financial decisions regarding whether repairs or new structures should be considered when compliance with standards is inconsistent. Replacing running or currently functioning heating, ventilation, and air conditioning systems that lack efficiency in comparison with newer systems is often not considered wise use of institutional resources. As this concern was faced and discussed during a recent campus AAALAC site visit to our institution, our IACUC requested additional information related to safe storage of feed in our current older buildings. Three test group environments of control/Guide for the Care and Use of Laboratory Animals (Guide)-recommended temperature/humidity, variable temperature/humidity, and high temperature/Guide-recommended humidity were used to store feed for a total of 6 mo. Full feed analysis, retinol levels, thiamine levels, and mold/yeast levels were evaluated at 0, 3, and 6 mo following storage. Study findings demonstrated that the nutritional content for feed remained relatively equivalent across the timespan as well as across the different storage conditions. More importantly, all storage conditions showed no increases in yeast/mold growth and acceptable levels of both thiamine and retinol at 6 mo. Our findings suggest that the diet tested was still usable for feeding animals after storage in the tested conditions that fall outside of Guide parameters and that other institutions may consider feed stability evaluation when addressing challenges with maintaining Guide parameters in feed storage spaces.

Humidity and temperature ranges for the control/Guide-suggested storage conditions (red), variable temperature and humidity (green), and hot with normal humidity (blue) conditions across the experimental time frame (April 2024 to October 2024). Ranges are represented as shaded fills where the bottom indicates the minimum value and the top indicates the maximum value recorded on the given date.

Depiction of our sampling method for feed bags within a biosafety cabinet. Each bag was surface-sprayed with Peroxiguard, a 4 × 4″ opening at the center of the bag was cut using a clean boxcutter, and a core feed sample was grabbed from the center of the bag to accumulate an additive 250-270g of feed for analysis.

Group means plotted for each nutrient measure across each of the baseline/day 0 (blue), month 3 (orange), and month 6 (green) time points split by control conditions (Guide-suggested storage conditions), variable conditions (variable temperature and humidity), and hot conditions (80 °F with normal humidity). The standard range of nutrient value acceptability based upon NRC recommendations is displayed as dashed, red lines for the top and bottom of the range.
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