Recommended Age of Neutering
Why Early neutering is bad
By Samantha Goldberg
The following article is a review of current literature and discussion about the
perils of early neutering.
Beagles are a medium sized breed and age of maturity of the skeleton
particularly bigger bones is at least 12 months. Testosterone and oestrogen are
involved in some of the long bone formations in the body so removing this too
early can affect correct growth leading to prolonged growth and poorer quality
bone with abnormal mechanical behaviours of the joints (1). Early neutering –ie
before skeletal growth has finished results in taller leggier hounds as the
closure of the plates in the long bones is helped by release of puberty
hormones. There is also increased risk of cranial cruciate rupture,
intervertebral disc disease, hip dysplasia and patella luxation being cited in
some breeds. The number of breeds listed as affected is likely to increase as we
Bitches may be sexually mature before the body has finished developing
physically and mentally. Although they may be able to come into season they have
not finished growing if under 12 months and will certainly not have finished
maturing mentally. Beagles will generally come into season when they have
reached at least 6 months of age but there is a big variation and some will be
18 months before they reach sexual maturity. Some families genetically are later
than others and it is best to be patient and not just neuter to suit the human
family. The season is only three weeks and a well crate trained beagle can cope
with plenty of chews and walks on a lead where the number of other dogs is low.
Many vets will try to influence owners to spey their bitch at 6 months and often
before a season. There was a paper (7) published many years ago looking at
mammary tumour development in bitches who had cycles. The table below lists the
number of dogs included which can be seen to be very low-24 in total. The risk
pre season is based on one bitch only and shows neutering between 1st and 2nd
season is still over 90% protective. (note the bottom two lines of the table are
the bitches from the third line portrayed in a different way).
Age at Neutering
Relative Risk of Mammary Neoplasia
Number of Bitches
and 2nd Season
2 or More
2 or More
Seasons but < 30 months old
2 of More
Seasons but >29 months old
Their study is widely quoted and there is no doubt that repeated cycles do
increase the risk as this is shown in countries where neutering is not routinely
practiced such as Scandanavia. However allowing one season allows many other
very important health issues to be reduced.
As vets in prepubertal bitches we commonly see cystitis, irritation around the
vulva and yellow/greenish vaginal discharges, which resolve once the bitch has
had a season. The prepubertal vulva is very small and often recessed allowing
skin irritation in the fold.
Urinary incontinence is more common in neutered bitches. In fact one of the
treatments for this is a low daily dose of oestrogen supplement. The
incontinence is caused by sphincter mechanism incompetence (SMI) which basically
means the tissue closing the neck of the bladder and which allows urination
under control becomes weak and involuntary urination occurs. A study (8) of
over 333,000 records using Vetcompass (an anonymised system which allows review
of UK veterinary practice records) showed an 3 times increased risk of neutering
and increased weight for SMI. Dogs over 10kg have an increased risk. This
applies to general body weight as well as obesity. In other words keeping your
dog slim is essential. There are not many beagles under 10kg mature correct body
weight but keeping them fit is a great help. SMI in male dogs is not very common
and weight control in males is needed for other reason.
Beagles are a breed bred to think for themselves whilst out hunting. Thus they
may be harder to recall and often get distracted when off lead, making yourself
more interesting than a hare is difficult! Neutering will not alter this! In
male beagles one of the commonest things I hear is “he runs off” “I think he is
looking for bitches”. Actually it is highly likely that dog is also hunting and
this is not driven by testosterone. A heedless teenage beagle is best trained
first and then neutered.
Teenage beagles generally need consistent guidance on how they fit in the family
pack. If they are neutered too young that behavior can become fixed as they need
to come out of puberty to be mentally mature. There is a lot of work looking at
behavioural issues with dogs in rescues and when they were neutered. So far it
seems likely that more dogs ending up in rescue with behavioural issues were
neutered early-ie under 12 months.
Neutering reduces metabolic rate and this means they need fewer calories or more
exercise to balance it. Often neutering is carried out without the vet warning
the owner of this. Thus we hear “she is overweight because she is speyed”.
Actually not true-being overweight is cause by eating more calories than are
expended. Overweight dogs have higher risks from many health condition-diabetes
mellitus, joint issues both due to increased mechanical strain and also
inflammatory mediators released the higher fat levels, and obvious things such
as heart disease due to increased work load.
Neutering male dogs directly reduces risks of increased prostate size due to
testosterone (not the same as tumours) and in bitches removes the risk of
pyometra a life threatening uterine condition and ovarian cancers. These effects
are very positive.
To summarise neutering should be carried out at the correct time to maximize
health in your dog and afterwards their life style may be changed a little eg
calorie control. Neuter to reduce risks of many health conditions but do it at
the right time to maximize the longevity of your beagle.
1. Salmeri KR, Bloomberg MS, Scruggs SL, Shille V. Gonadectomy in immature dogs:
effects on skeletal, physical, and behavioral development. J Am Vet Med
2. Slauterbeck JR, Pankratz K, Xu KT, et al. Canine ovariohysterectomy and
orchiectomy increases the prevalence of ACL injury. Clin Orthop Relat Res 2004;Dec(429):301-305.
3. Whitehair JG, Vasseur PB, Willits NH. Epidemiology of cranial cruciate
ligament rupture in dogs. J Am Vet Med Assoc 1993;203(7):1016-1019.
4. Torres de la Riva G, Hart BL, Farver TB, et al. Neutering dogs: effects on
joint disorders and cancers in golden retrievers. PLoS One 2013;8(2):e55937.
5. van Hagen MA, Ducro BJ, van den Broek J, Knol BW. Incidence, risk factors and
heritability estimates of hind limb lameness caused by hip dysplasia in a birth
cohort of boxers. Am J Vet Res 2005;66(2):307-312.
6. Vidoni B, Sommerfeld-Stur I, Eisenmenger E. Diagnostic and genetic aspects of
patellar luxation in small and miniature breed dogs in Austria. Eur J Comp Anim
7. Schneider R, Dorn CR and Taylor DON (1969) Factors influencing canine mammary
cancer development and postsurgical survival. Journal of the National Cancer
Institute 43, 1249-1261.
8. Pegram, C. , O'Neill, D. G., Church, D. B., Hall, J. , Owen, L. and Brodbelt,
D. C. (2019), Spaying and urinary incontinence in bitches under UK primary
veterinary care: a case–control study. J Small Anim Pract. doi:10.1111/jsap.13014