Syringe feeding is only necessary when an animal cannot or will not feed by itself, for example after dental surgery or during periods of anorexia. Fostering babies requires different techniques and is covered under Handrearing
Syringe feed should consist of a veterinary formula such as Critical Care or a home made formula based on the animal's natural diet. A formula for guinea pigs should contain adequate fibre as it is important that the motility of the gut is maintained. Powdered and soaked pellets form a good base. A coffee grinder makes a good pulveriser for pellets. Pure dried grass makes an excellent food when powdered but I'd advise you to freeze it first as its low moisture content (3%) means it heats up very quickly in the grinder.
Unsweetened canned pumpkin is considered a good syringe feed. Other useful ingredients include baby cereal mixed with alfalfa (to balance out the calcium to phosphorous ratio); super foods such as those containing wheatgrass, barley grass, chlorella, spirulina, pollen, fruit and vegetable powders etc. The most complete and balanced single food for rabbits is grass. Grassmeal is available from the Specialist Shop.
Care must be taken with dietary fibres used for humans including bran, which is a good source of energy but not indigestible fibre for these animals, and psyllium husk which swells when mixed with water. Useful in small amounts as a source of energy, psyllium husk used to excess can cause digestive blockage. Ground hay is the best source of indigestible fibre, although unmedicated straw can also be used.
At Galen's Garden we now have a new version of our own syringe feed powder, NutriPowder. NutriPowder has been designed using all natural ingredients to be high in fibre with a balanced Ca:P ratio. Ingredients include grass, alfalfa, nettles, rosehips, barley grass, beetroot, carob, carrot, chicory root, cleavers, cornsilk, dandelion leaf, fenugreek, golden rod, inula, irish moss, marshmallow root, oatmeal, plantain leaf and husk, slippery elm bark and wheat grass.
You should wean the animal off of syringe feeding as soon as possible. Syringe feeding can make the animal lazy or too full to eat normally and this impacts on the teeth which need the regular chewing motion to grind them down to a normal length.
Make the syringe mix increasingly thick using less and less water to encourage chewing, eventually making it so thick that you can roll it into small balls that you place on the back teeth to encourage chewing. Give plain water after this if you are really worried that the animal isn't getting enough fluid but at this stage the animal should be drinking normally.
Animals which have become dehydrated may need subcutaneous or intravenous fluids from the vet, or oral rehydration therapy using an electrolyte solution. Once the fluid balance has been restored, normal hydration using plain water can be resumed. You should not use veterinary rehydration solutions containing mineral salts (sodium, chlorine, potassium) and sugar (glucose), or syringe feed solutions which contain remedial amounts of salt and sugar, unless prescribed by your veterinary surgeon.
Stress, surgery, antibiotics and diarrhoea can all cause a reduction in the levels of good bacteria in the gut. It is advisable under those circumstances to add a good veterinary probiotic to the syringe feed mix. Prebiotics, the substances which provide a fertile substrate in which beneficial bacteria can grow, should also be included. Galen's NutriPowder does not contain probiotics but does contain chicory root and inulin, both natural sources of the prebiotic FOS, fructo-oligo-saccharides. If you can obtain them, the caecal pellets from a healthy rabbit, guinea pig or chinchilla can be added to the syringe feed mix. And, before you go all "Yuck!" and squeamish or hygienic on me, remember that your guinea pig eats them on a daily basis because they are a rich source of protein, B Vitamins and good bacteria.......
Many syringe feed mixes are so thick that they block the hole in syringes with even the widest available hole. The answer is either to use a tiny coffee spoon for feeding, or to use a soft plastic pipette and cut off the end so the feeding hole is large enough. Thick syringe feeds are a good thing, as not only are they more easily formed into soft pellets to get the rabbit, guinea pig or chinchilla eating normally, but that thickness is also an indication that the fibres in the mix are long enough to act as indigestible fibre if they are lignified fibre. Indigestible (lignified) fibres should be at least 2.5mm in length to ensure the good gut motility essential for the wellbeing of the animal. Even beneficial lignified or indigestible fibre, if ground too finely, will pass through the digestive system as carbohydrate or energy as opposed to the type of fibre which acts to move the other food through the gut in a healthy manner.