Figure 1 . Ad libitum hay is essential for maintaining health status . Photo : The Potato Patch Guinea Pig Hotel & Sanctuary .
Generally , owners should be advised to seek hay that is sweet-smelling and pale green to golden in colour . The two most common types available in the UK are meadow hay and Timothy hay . Meadow hay consists of a mixture of native pasture grasses and usually has a softer texture and a high quantity of leaves , such as thistle and dandelion , which add variety . In contrast , Timothy hay consists of one single species of perennial grass and is lower in leaf content , but it has a high fibre content and slightly rougher texture [ 13 ] . Current thinking is that the variety in meadow hay contributes to improved GI health , whereas the texture of Timothy hay supports dental health , so a combination of the two types could be a suitable option . Alfalfa hay should be avoided as a main source of hay in non-nursing adults , due to its high calcium and protein content [ 13 ] .
Guinea pigs have unusual dentition , possessing openrooted teeth that erupt continuously [ 14 ] and grow an estimated 1 – 2 mm per week . Insufficient dietary fibre is likely to lead to malocclusion , dental spurs , pain and associated anorexia , which is a significant concern in these rodents , which generally spend most of their waking hours grazing . Even short periods of anorexia can cause slow GI peristalsis , often leading to ileus and associated ketoacidosis [ 9 ] . It is therefore essential to ensure that quality dietary fibre is provided ad libitum , not only to maintain the digestive and dental health of the animal but also to reduce the risk of potentially lethal associated disease .
When considering preventive health care and nutrition , it is vital to assess the potential impact of vitamin C deficiency on this species as , interestingly , guinea pigs cannot synthesise vitamin C and so require a daily supplement in their feed . Chronic hypovitaminosis C ( scurvy ) is considered a predisposing factor for a range of diseases , including pneumonia and enteritis [ 9 , 14 ] , so owners should ensure their pets receive adequate quantities of vitamin C in their daily feed .
A guinea pig ' s diet should contain 10 mg / kg vitamin C daily [ 11 ] within a balanced diet . Required levels of dietary vitamin C can be obtained through the provision of a formulated guinea pig pellet . Care should be taken to select a species-specific feed , as rabbits and most other rodents do not require dietary vitamin C and do not , therefore , need supplemented pellets [ 14 ] . Feeding a muesli-type diet is not appropriate , due to the high sugar content that can encourage selective feeding , leading to dietary deficiencies [ 10 , 15 ] . Good-quality commercial guinea pig pellet feeds will contain the correct quantities of stabilised vitamin C . It is important to advise owners that vitamin C will degrade when exposed to UV light , will break down faster when stored at high temperatures and should not be kept beyond the use-by date [ 15 ] . Owners should adhere to the recommended feeding quantity to avoid obesity and associated issues [ 11 ] ; for an average-sized adult guinea pig , this is surprisingly small at around 1 tablespoon of pellets per day [ 15 ] .
Alongside the provision of good-quality roughage and commercial pellets , guinea pigs should also be provided with fresh vegetables , which serve as another suitable source of dietary vitamin C and provide
[ 10 , 16 ] gustatory and exploratory enrichment . Sources suggest that bell peppers , spring greens and tomatoes are particularly beneficial due to their high vitamin C content . Other suitable options include but are not limited to pak choi , baby corn , carrot tops , rocket , several lettuce varieties ( including butterhead and cos ) and herbs such as basil , mint and coriander [ 15 ] . Fresh produce should be fed in moderation , to avoid complications such as diarrhoea . Some vegetables , such as broccoli and kale , are high in calcium , and large quantities are thought to contribute to diseases such as urolithiasis and renal calcification [ 10 ] .
There is mixed literature on the feeding of fruit to guinea pigs . Owing to its high sugar content , it is advisable to feed fruit to guinea pigs only in small quantities , as an occasional treat [ 10 ] . The PDSA recommends feeding guinea pigs an approximate teacup-sized quantity of fresh produce daily [ 16 ] , while others suggest that irregular fresh feeding may be more appropriate [ 14 ] .
It has been reported that many guinea pigs in the UK are not receiving the correct amount of fresh greens [ 17 ] , which suggests that this is an area for improvement when considering nutritional planning . Regardless of the frequency of feeding , the nutritional value of some fresh greens to guinea pigs is evident , with a recent study [ 18 ] finding that the number of reported health issues was lower in animals receiving green vegetables more often .
Easy access to clean drinking water is also important for guinea pigs , as it is known to benefit homeostatic processes and reduce the incidence of certain diseases including urolithiasis [ 19 ] . On average , guinea pigs will take in around 10 ml of water per 100 g body weight daily [ 20 ] , but this may be higher if moist foods are not
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