Plus-Hex CLINICAL which foodstuffs and water bottles with added tablets left out in enclosures are highly susceptible, as well as unpalatable tablets and suboptimal concentrations in the water, which make it impossible to ingest an adequate amount of vitamin C without drinking an excessive volume of water [ 65, 66 ]. However, it may take around 3 months for pellets to lose their vitamin content and they are usually consumed much faster, especially if multiple guinea pigs are being kept together [ 13 ]. Therefore, pellets can be a sensible way to provide vitamin C.
Norman and Wills [ 50 ] and Witkowska et al. [ 51 ] both found that fresh food was given at least daily, which may indicate more frequent replacement of stale food. However, quality cannot be assessed, and specific type( s) of either fresh food or vitamin supplementation are unknown. Providing garden plants, described by Norman and Wills [ 50 ], is concerning, as many are toxic to guinea pigs [ 67 ], but owner knowledge of this has not been quantified.
Hypervitaminosis C is also harmful and possible if owners use multiple concurrent supplementation methods [ 68 ]. Urolithiasis, arthritis and poor growth are consequences, with the risk being exacerbated if commonly recommended vegetables such as cabbage or broccoli, which are high in vitamin C and calcium, are fed too often [ 16 ]. A handful of pellets and fresh vegetables daily is recommended, and appropriate vitamin dosage should be discussed with owners [ 28, 69 ].
‘ Pseudo-scurvy’, a phenomenon in which deficiency arises from acquired diminished sensitivity, is possible. This is undesirable in a species that relies on dietary vitamin C. However, more research is needed as the available literature is dated [ 70, 71 ].
Witkowska et al. [ 51 ] found some owners feeding their guinea pigs rabbit food. It was interesting to find a study that investigated its suitability. However, only fortified rabbit food was investigated, so suitability by itself is unknown; no long-term health impacts were considered, and species-specific foods are often nutritionally unbalanced in other species [ 72 ].
Housing and husbandry
bodies or charities [ 76 ]. Encouragingly, Cameron et al. [ 52 ] found that indoor guinea pigs mostly had permanent runs and, although primary housing excluded runs in Harrup and Rooney [ 49 ], regular exercise in separate areas was provided.
It was, however, found that commercial hutches or cages were the smallest enclosures used, corroborating the need for retailers to be more welfare-oriented through further education and legislative reform to enforce minimum welfare standards.
Guinea pigs are not avid climbers, so floor space supersedes height in importance; multiple levels are not a solution and positive behaviours such as‘ popcorning’ require space [ 77 ]. Additional floors, however, are enriching if they have acceptable proportions and ramps are not steep enough to cause accidental injury [ 13 ]. From the findings, the impact of multiple levels is unknown, and more research would be useful.
Temperature extremes, such as prolonged exposure to direct sunlight and draughts, have detrimental consequences including stunted development and stress responses that are transgenerational [ 73, 78 ]. Around 16 – 24 ° C with 40 – 70 % humidity is suitable, but some sources recommend even lower humidity [ 16, 75 ]; this requires further exploration and was not specifically addressed in the six studies. When temperatures are below 15 ° C and if guinea pigs are in uninsulated outdoor homes, it is suggested they be moved inside [ 79 ]. At temperatures above 26 ° C, they must be moved into a cool area and should, ideally, already have shaded areas available for choice [ 75, 79 ]. Outdoor enclosures can be proofed against wind, rain and snow, providing there is sufficient airflow, but temperatures are more easily monitored inside homes [ 79 ].
Outdoor housing must be fully enclosed and secure to protect against predators [ 22 ] and provide shade during warmer weather( Figure 5). Aquaria do not provide suitable ventilation and are never recommended [ 75 ]. From the findings, owner knowledge of these aspects and whether they were specifically considered is unknown, and exploring the reasons for accommodation choices would have been favourable.
Enclosed spaces of adequate size are required for safety, exercise and mental stimulation [ 73 ]. Injury can result from other animals or people, chewable electrical cords and toxic houseplants [ 16, 74 ]. Minimum enclosure size standards are unclear; for example, Mancinelli and Bament [ 17 ] state that 700 cm ² should be provided per guinea pig, whereas RSPCA Victoria [ 75 ] recommends a larger space of 2,500 cm ² for a pair.
Harrup and Rooney [ 49 ] and Cameron et al. [ 52 ] reinforced the impact of location-related variation in ownerreachable information, by finding deviations in housing size compared with recommendations from governing
Figure 5. Shade provided over an outdoor access area.
Volume 40( 5) • October 2025
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