Nutritionist and natural care adviser here.
In my opinion and based on most of my research, i live in a 3rd world country. Spaying and neutering is required IF you as an owner aren't going to/ can't commit on managing and containing you're pets when females are in season or males that want to roam or mark territory,along with other behavioral and hormonal problems that come with intact pets.
If you can and are willing to, best bet in order to preserve health and avoid Future issues regarding early desexing, is for big dog breeds wait til 2 yrs of age. For small breeds wait til one year. At this time growth plates have completed closure and your dog is no longer growing mentally or physically. At 3 years in any breed there are little or no risk associated with desexing. They are minor or have little impact.
On cats, spay and neuter at 5/6 months of age. In felines there's been no documented I'll effects of early spay/ neuter. It's actually better for them.
Id you have males, you can manage them with training and offer a hand
.
Same for females.
Separate males from females ASAP you see the earliest indication of heat. This means until bits over they can't see or smell each other. Crating and limiting spaces. Makes can't smell anywhere she so much as sat down in. They go on walks prior to the girls EVERY TIME and no sniffing through doors.
IT WORKS. The problem are the pheromones from the vulva,as soon as makes get a whiff of her urine,fluids or genitals,game over. Id they don't, they will acknowledge the presence of one but won't know it's in the home. Just as if she was away with a friend, which is also an option.
If you have a pair or want some sort of peace of mind, Do Ovary Sparing Spay or Vasectomy. Preserves hormones ultil growth is complete, but they can't produce off spring. In males it can be Reverted if you decide to breed (responsibly).
If you must neuter or spay early wait til 6 months and supplement with supplements for glandular support like Mercola's that will supply the missing hormones to fuel correct skeletal and muscular development. It won't cause season or sexual hormone related behaviours.
That's all i have to offer. Hope it helps. I did management for 4 years with males and a female with no issues.
Personally y keep males intact. Because most of they're hormone related problems are behavioral and can be modified, neutering only has a 50% chance of decreasing them.