- Schrägblattrührer [masculine]
- oblique agitator blade
- oblique agitator blade
- OCB
- occupancy cycle
- ocular anomaly
- odour
- oestrus period
- oestrus synchronisation
- oil boiler
- oink
- on the pressure side
- on the suction side
- on-the-floor feeding
- one-arm
- one-line
- one-way gate
- one-way valve
- open combustion
- open float drinker
- open house
- open run
- open run
- open-air pig house
- open-air run
- opening
- operator
- optical scale(s)
- organic house
- organic layer
- outdoor sow farm
- outer aisle
- outside air flap
- outside silo
- outside temperature
- overall farm sanitation management
- overflooding mechanism
- overhead tank
- overpressure
- overshoe
- oxygen measuring unit