Dietary phosphorus restriction enables multigenerational breeding of α-Klotho-deficient rats

Severe α-Klotho deficiency causes early mortality and reproductive impairment, limiting the maintenance and physiological analysis of rat models. We generated rats carrying a CRISPR/Cas9-mediated α-Klotho deletion spanning exons 1–5 and evaluated dietary phosphorus restriction primarily in the Wistar-Imamichi background. Maternal low-phosphorus (LP) feeding from mating through lactation was associated with higher overall survival to weaning (92.6% versus 85.8% under normal-phosphorus conditions) and a higher proportion of KO animals among weaned survivors (34/113 versus 23/145). Maternal LP feeding also reduced plasma phosphorus in KO pups. Continued LP feeding after weaning supported growth, gonadal development, and natural KO × KO breeding. Across 15 litters, 74 of 85 offspring survived to weaning, and KO colonies were maintained to at least the fifth generation. We additionally characterized 24-h metabolic rhythms in LP-maintained KO animals using indirect calorimetry. These profiles remained heterogeneous under a light–dark cycle. In conclusion, dietary phosphorus restriction provides a reliable strategy for the multigenerational maintenance of severe α-Klotho-deficient rats, establishing a maintainable model to investigate residual metabolic and physiological phenotypes.