The University of the Philippines (UPLB) Vet Hospital is located close to the "back" gate of IRRI, but still within the IRRI campus. It is the Veterinary Teaching Hospital for UPLB and offers a wide range of services for your pet care like vaccinations, check-ups, spay/neuter services etc.
There is also a Dog Groomer just outside the "back" gate of IRRI called "Furbabies & Friends". They also do vaccinations and have a variety of accessory, foods, and medications for your pets.
Pet food and supplies are available in many other stores and shops in the Philippines.