Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
I am very concerned about your wee lass.
As I am sure you are aware, anorexia is very serious in this species (it is one of the few emergencies for this species). Guinea pigs are designed to be eating all the time, as they have a gastrointestinal tract that is like conveyor belt and needs to be moving/digesting all the time. And if they aren't, then their guts ground to a halt, this can lead to serious consequences. Namely, the bacteria naturally in the system overgrow and release gas (painful!!) and toxins, which cause a pig to get even sicker and less keen to eat or drink.
If she is showing this appetite decline already, it would really be ideal to seek your veterinarian’s assistance now to give her the best chance of survival. The vet can identify the trigger for her signs and address this, while also tackling the GI side of this issue. Ideal therapy would be combination of hydration (best done with fluids under the skin by your vet), antibiotics, promotility drugs (to restart gut movement), and pain relief.
While your vet can show you how to syringe feed them, you will also find a good outline for hand feeding ill guinea pigs @ HERE . It is worth speaking to the vet about diets to syringe feed to guinea pigs. I tend to use Oxbow’s Critical Care feed (HERE) or Supreme Recovery diet for anorexic guinea pigs. These are highly nutritious herbivore feeds that can be easily made into a slurry for syringe feeding. And it is much easier to use then trying to create a balanced critical care diet at home. Though while you are sorting out getting her seen, you can syringe veggie baby food or even make a gruel of crushing pellets and rehydration solution (ie pedialyte) to get some nutrition into her until you can get her seen.
Furthermore, if she is drinking poorly or you are concerned that she might be becoming dehydrated, you can try and encourage her to drink by offering fresh water. If he is not amenable then you can also try flavored pedialyte or diluted Gatorade (50% diluted with water). These will help replenish electrolytes and get some glucose into his system as well as get fluids in. You can also give pedialyte via dropper of syringe. A typical dose for animals is 4.8mls per 100 grams of body weight per day (obviously divided over all day drinking).
Overall anorexia in the guinea pig is a very serious situation and aggressive treatment is necessary to help her overcome this. Therefore, it would really be worth considering having her seen urgently (even as an emergency tonight). The sooner you address this situation for her, the better chance you can get her eating and better chance you can get her back on track.
Finally, just to note in case you were keen to have her seen now, most vets here do have contingency plans for emergency care for their patients even when they are not open. Therefore, it is worth ringing the practice. If they are open, you can get her seen today. If they aren't, then they will likely have a message to direct you on how to contact their out of hours service. And if you don't have a vet you can find one local to you, you can check the RCVS Register (HERE) to find your local vets or Vets Now (LINK) who are open all nights/weekends. In any case, if you wanted to get her checked out urgently then there are options to have her seen.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and hope to see you again soon! : )