Daily replacement of very high-fat diet stabilizes food intake and improves mouse welfare by ensuring food quality

Researchers are obligated to ensure food quality and provide laboratory animals with a palatable diet. Factors influencing the quality and palatability of very high-fat diet (VHFD), a widely used rodent diet, however, are understudied. We conducted experiments to establish best practices for ensuring the quality of VHFD and to improve mouse welfare. We found that VHFD in the food hopper was vulnerable first to dehydration and then oxidation within 7-days, leading to dramatic changes in food intake and food preference behavior in mice. Mitigating dehydration and oxidation of VHFD by replacing food daily, rather than weekly, stabilized feeding behavior without effect on overall cardio-metabolic health. Importantly, daily replacement of VHFD also reduced measures of anxiety-like behavior in the open field test. Refining husbandry practices to include daily replacement of VHFD can therefore ensure VHFD quality and improve animal welfare. Standardizing the practice of daily VHFD replacement may also prevent experimental confound and improve experimental reproducibility and replicability.