Study proposes new way to prioritize shelter sterilization slots
Bottom line
A new mathematical modeling study in the American Journal of Veterinary Research proposes a different way for shelters to decide which adoptable animals should get limited pre-adoption sterilization slots first. Rather than automatically moving the easiest-to-adopt, “fast-track” animals to the front of the surgery line, the model argues shelters should prioritize whichever animal’s surgery deferral would add the most to expected length of stay. The author defines that impact using each animal’s baseline expected length of stay, adopter aversion to adopting before sterilization, and how surgery delay changes adoption timing. The study arrives as shelters continue to manage surgical bottlenecks and longer stays for animals that arrive intact. (shelteranimalscount.org)
Why it matters: For veterinary professionals in shelters, the paper reframes sterilization scheduling as a population-management decision, not just a first-in, first-out or fast-track workflow issue. That matters because length of stay is tightly linked to crowding, disease pressure, staffing strain, and welfare outcomes, and national shelter data show prealtered dogs and cats move through shelters faster than animals that need surgery on-site. The practical takeaway is that limited surgery capacity may have the biggest system-wide benefit when directed to animals whose delay most inflates overall stay, especially in shelters already operating near capacity for care. (pmc.ncbi.nlm.nih.gov)
What to watch: Whether shelters or shelter medicine programs turn this theoretical framework into triage tools, dashboard rules, or prospective field studies that test it against current fast-track practices. (pmc.ncbi.nlm.nih.gov)
A new study in the American Journal of Veterinary Research takes aim at a familiar shelter bottleneck: what to do when adoptable animals must be sterilized before placement, but surgery capacity can’t keep up. The paper, by Michael L. Mavrovouniotis, presents a mathematical model for prioritizing animals for sterilization based on which delay would have the greatest adverse effect on expected length of stay, instead of relying on simpler rules like first-come, first-served or always prioritizing the most readily adoptable animals. (pmc.ncbi.nlm.nih.gov)
That question lands in a field already under pressure. Shelter medicine guidance has long tied shorter length of stay to better welfare, lower disease burden, and better use of fixed staffing and housing resources. At the same time, many operational playbooks have encouraged “fast-tracking” highly adoptable animals, including giving them priority for immediate surgery so they can move quickly to the adoption floor. (bestfriends.org)
The tension is that those instincts may not always produce the lowest average census. In a related 2026 theoretical study, Mavrovouniotis found that when limited promotional or premium-kennel resources were directed to slow-track rather than fast-track animals, the modeled shelter census was lower, because reducing long stays had a larger population-level effect than making short stays even shorter. That paper focused on marketing and kennel allocation, but it provides important context for the new sterilization-prioritization model: the biggest operational gain may come from targeting the animals whose delays are most costly to the whole system. (pmc.ncbi.nlm.nih.gov)
The broader backdrop also supports why this matters now. Shelter Animals Count reported that from 2019 to 2023, the share of animals entering shelters already altered fell from 33.2% to 22.3% for dogs and from 27.9% to 22.0% for cats. Those prealtered animals consistently had shorter lengths of stay than animals requiring surgery in the shelter, and the University of Florida Shelter Medicine Program said the gap in 2023 was four days for dogs and 11 days for cats. In other words, every surgery backlog now carries more operational weight than it did when more animals arrived already sterilized. (shelteranimalscount.org)
Expert reaction specific to this paper was limited in publicly available sources, but the surrounding field guidance points in the same direction: shelters should manage flow with the whole population in mind. Best Friends’ length-of-stay guidance says fast-tracking can create space and free staff time, while also emphasizing proactive daily planning for longer-stay animals to reduce crowding, disease prevalence, cost, and welfare harms. Association of Shelter Veterinarians materials likewise connect capacity-for-care management and reduced length of stay with improved outcomes. Taken together, the new paper appears less like a rejection of fast-track logic and more like a push to use a more quantitative, case-by-case rule when surgery slots are scarce. That last point is an inference based on the study’s framing and existing shelter operations guidance. (bestfriends.org)
Why it matters: For shelter veterinarians, HQHVSN teams, and operations leaders, the study offers a framework for making a hard daily decision more defensible. If an intact animal’s delayed surgery is likely to substantially prolong stay because adopters are reluctant to commit before sterilization, moving that case up could reduce average census more than expediting an animal that was likely to leave quickly anyway. In crowded systems, that can translate into less stress, less infectious disease exposure, fewer overflow housing compromises, and more clinical bandwidth for preventive and behavioral care. (pmc.ncbi.nlm.nih.gov)
There are still limits. The available public description indicates this is a mathematical modeling study, not a prospective shelter trial, and models depend on assumptions about adopter behavior, baseline adoptability, and local workflow. Shelters would likely need usable proxies, such as historical length-of-stay patterns, species, age, housing location, and adoption-hold behavior, to operationalize the framework. The next meaningful step will be validation in real shelter settings, especially in organizations balancing legal sterilization requirements, limited HQHVSN capacity, and fluctuating intake. (pmc.ncbi.nlm.nih.gov)
What to watch: Expect interest in whether shelter software, daily rounds, or surgery scheduling protocols can convert this kind of model into simple prioritization rules, and whether future field studies show measurable reductions in average length of stay, overflow use, or disease risk when those rules replace standard fast-track scheduling. (pmc.ncbi.nlm.nih.gov)