To submit the VMCAS, a minimum of 3 recommendations are required and a maximum of 6 will be accepted. Unlike medical school, committee letters from the HPA are not required. Most schools require that at least one of the 3 recommendations is from a vet. Recommendations can also be submitted by academic advisors and professors. Some schools are also open to accepting additional non-standard rec letters from individuals that are not from the university or veterinary profession. This could include a mentor, high school teacher, or supervisor for your non-veterinary experiences. Letters from family members or friends are usually not recommended.
Rec letters are used by schools to assess your abilities through the eyes of professionals. They can sometimes even make or break applications if admission officers see red flags such as lack of communication skills and immaturity. When deciding who to ask recs from, make sure you have had at least somewhat of a close personal and professional connection to the vet/professor/mentor. Moreover, make sure you have had mostly positive experiences with them otherwise you might just be asking for a vet school rejection.
HPA offers the opportunity to store copies of letter of recommendations for up to 6 years past your graduation year so that you don’t have to awkwardly keep asking old contacts to write you letters. However, HPA may still not be able to submit the letters to VMCAS on your recommender’s behalf. Contact HPA for more details regarding rec letter storage and/or visit this link. This link also includes tips for when and how to professionally ask for recs (the info is tailored mostly for pre-meds, but it should still be useful)!