Neutering and Spaying Dogs: What the Evidence Says

The "always spay/neuter" recommendation has been the default in many countries for decades. The scientific picture has become significantly more nuanced, particularly for large breeds, revealing both substantial benefits and real risks that vary by sex, breed, and age at procedure. Here's a balanced, evidence-based overview.

What Do the Terms Mean?

• Spaying (female): ovariohysterectomy (removal of ovaries + uterus) or ovariectomy (ovaries only). Both eliminate hormones.
• Neutering/castration (male): orchiectomy — removal of both testes
• Chemical castration (male): GnRH implant (deslorelin) provides 6–12 months of reversible suppression — useful as a trial before surgical decision

Benefits

• Females: eliminates heats and associated behaviours, pyometra (life-threatening uterine infection — affects ~25 % of intact females by age 10), and false pregnancies. Dramatically reduces mammary tumour risk if performed before the first heat (~0.5 % risk vs ~26 % after two heats).
• Males: eliminates testicular cancer, reduces benign prostatic hyperplasia risk, may reduce urine marking and roaming in testosterone-driven individuals.
• Eliminates unplanned litters.

Real Risks (Especially Large Breeds)

• Weight gain: neutered dogs have 20–30 % lower resting metabolic rate. Feed accordingly — weight gain is preventable but virtually certain if food intake doesn't change.
• Urinary incontinence (females): risk increases in medium to large breeds, especially with early spaying
• Orthopaedic disease: multiple studies in Golden Retrievers, Labradors, German Shepherds, and other large breeds show increased risk of hip dysplasia, elbow dysplasia, and cranial cruciate ligament rupture when neutered before growth plates close
• Certain cancers: neutered dogs of large breeds show increased rates of haemangiosarcoma, osteosarcoma, and mast cell tumours in some studies

Timing Recommendations

• Small breeds (<15 kg): before or after first heat — low risk either way
• Medium breeds: after growth completion (~12–15 months)
• Large and giant breeds: many specialists now recommend waiting until 18–24 months. The individual risk-benefit balance depends on behaviour, living situation, and breed-specific data.

Log your dog's neuter date and age at procedure in Purzi. It's medically relevant for future consultations — urinary incontinence, weight trends, hormone-related screening.