| Abbreviation | Definition |
|---|---|
| UKC | United Kennel Club |
| UKCC | United Kingdom Central Council (for nursing, midwifery, and health visiting) |
| UKERF | University of Kentucky Equine Research Foundation |
| UKFOMPO | United Kingdom Federation of Milk Producing Organisations |
| UKRCB | UK Registry of Canine Behaviourists |
| UKROFS | United Kingdom Register of Organic Food Standards |
| UKWCT | UK Wolf Conservation Trust |
| UKXIRA | United Kingdom Xenotransplantation Interim Regulatory Authority |
| USAHA | United States Animal Health Association |
| USD | Unified School District |
| USDF | United States Dressage Federation |
| USDHHS | United States Department of Health and Human Services |
| USDOI | United States Department of the Interior |
| USDOT | United States Department of Transportation |
| USFWS | United States Fish and Wildlife Service |
| USLR | United States Lipizzan Registry |
| USMEF | United States Meat Export Federation |
| USPCA | Ulster Society for the Prevention of Cruelty to Animals |
| UVAS | University of Veterinary and Animal Sciences |
| UVCE | Unit for Veterinary Continuing Education (of the RVC) |