In general, unless there are exceptional reasons not to do so, there are many benefits (practical, medical and behavioural) in recommending that an animal be neutered.

Dogs would generally be castrated from 1 year onwards (although it would be considered earlier if your veterinary surgeon felt it were in the animal’s best interests to do so).

Spaying of bitches  we would recommend be carried out 4 months after the start of the first season (provided that the bitch is not experiencing a false pregnancy at this time).

Cats should routinely be neutered at 6 months of age.

Rabbits - males can be castrated from 16 weeks onwards and females can be spayed from 5 months.

Any disadvantages?

There could be minor disadvantages such as change in coat texture/colour or a predisposition to weight gain (although this can be counteracted by a sensible feeding regime) but your veterinary surgeon will be pleased to discuss the matter in detail with you so that you can make an informed decision in the best interests of your pet.