What age to neuter large breed dog

Q: What happens if you neuter a large breed dog too early?

While some veterinary experts continue to recommend neutering earlier, others agree that large breeds may experience some health issues, including joint problems like knee injuries and hip dysplasia if neutered too early (prior to one year old).

Q: Do male dogs get bigger after being neutered?

NOPE! Although, without some changes in behavior, it can happen. Spaying or neutering your dog or cat doesnt cause your pet to become overweight or obese. However, neutering is linked to an increased risk of weight gain if no change is made to what and how much you feed your pet after the surgery.

Q: Do dogs get more aggressive after being neutered?

A: Yes, its quite common for male dogs to experience an increase in aggression after being neutered. Neutering your male dog can also cause behavioral symptoms such as increases in fearful behavior, hyperarousal, and more.

Updated July 28, 2022

Table of Contents Show

Dogs 30-39kg
Dogs 40+ kg
Summary: The Best Large Dog Spay & Neuter Times
Problems With This Study
What happens if you neuter a large breed dog too early?
Do male dogs get bigger after being neutered?
Do dogs get more aggressive after being neutered?

Whether you call it neuter, spay, castrate or desex, the right time to get it done in dogs is a subject of much debate. This is because it varies from breed to breed. Recently, a study was published on the best age for neutering large dog breeds.

The study actually looked at 30+ kg crossbreeds but this data should be the closest match to a large breed currently available if it isn’t in covered this list.

While the paper isn’t perfect (more on that later), it does provide the first evidence for large-sized dog breeds on choosing a time of desexing with the fewest health problems. The study compared the dogs neutered at different ages for their rates of:

joint disorders: hip dysplasia (HD), cruciate ligament injury (CCL) and elbow dysplasia (ED)
cancers: lymphoma (LSA), mast cell tumour (MCT), haemangiosarcoma (HSA), osteosarcoma (OSA)
urinary incontinence (UI)

All of these have been suspected to be linked with the age of neutering. Here’s what they found (only bold values are significant, after the four tables you will find my summary):

Dogs 30-39kg

HDCCLEDAt Least OneMale < 6 months2/41 (4.88)6/45 (13.33)0/43 (0)7/41 (17.07) †Male 6 – 11 months2/38 (5.26)3/46 (6.52)0/45 (0)4/37 (10.81) †Male 1 year1/50 (2)0/51 (0)1/51 (1.96)1/50 (2)Male 2 – 8 years0/44 (0)0/46 (0)1/48 (2.08)1/45 (2.22)Male Intact7/173 (4.05)5/177 (2.82)4/174 (2.3)13/174 (7.47)Female < 6 months1/31 (3.23)3/32 (9.38)0/33 (0)3/30 (10) †Female 6 – 11 months4/50 (8)8/48 (16.67)1/51 (1.96)11/47 (23.4) †Female 1 year0/35 (0)1/37 (2.7)0/38 (0)1/34 (2.94)Female 2 – 8 years0/50 (0)2/50 (4)0/51 (0)2/48 (4.17)Female Intact0/55 (0)0/57 (0)0/57 (0)0/55 (0)Joint Disorders. For ages 1 through 11 years and for each neuter period. Bold values indicate significance over the intact group. The dagger (†) indicates significance over the intact group when the early groups (< 6 mo. and 6-11 mo.) are combined.LSAMCTHSAOSAAt Least OneMale < 6 months2/42 (4.76)0/43 (0)0/45 (0)0/45 (0)2/42 (4.76)Male 6 – 11 months2/46 (4.35)0/44 (0)2/45 (4.44)0/46 (0)4/44 (9.09)Male 1 year0/51 (0)1/51 (1.96)1/51 (1.96)1/51 (1.96)3/51 (5.88)Male 2 – 8 years1/48 (2.08)1/47 (2.13)0/48 (0)0/48 (0)2/47 (4.26)Male Intact13/175 (7.43)6/176 (3.41)1/174 (0.57)5/174 (2.87)25/172 (14.53)Female < 6 months1/32 (3.13)2/33 (6.06)0/33 (0)1/33 (3.03)4/32 (12.5)Female 6 – 11 months0/50 (0)2/50 (4)1/51 (1.96)0/50 (0)3/48 (6.25)Female 1 year1/38 (2.63)1/37 (2.7)1/37 (2.7)0/38 (0)3/37 (8.11)Female 2 – 8 years0/51 (0)2/52 (3.85)0/52 (0)1/52 (1.92)3/51 (5.88)Female Intact5/56 (8.93)1/57 (1.75)0/56 (0)1/57 (1.75)7/55 (12.73)Cancers. For ages 1 through 11 years and for each neuter period: no significant findings.

Dogs 40+ kg

HDCCLEDAt Least OneMale < 6 months2/17 (11.76)5/18 (27.78)0/18 (0)5/18 (27.78) †Male 6 – 11 months1/27 (3.7)2/28 (7.14)0/27 (0)3/27 (11.11)* †Male 1 year0/20 (0)1/19 (5.26)2/21 (9.52)2/19 (10.53)Male 2 – 8 years0/36 (0)0/32 (0)0/36 (0)0/32 (0)Male Intact1/86 (1.16)7/91 (7.69)0/86 (0)8/87 (9.2)Female < 6 months1/11 (9.09)1/12 (8.33)0/11 (0)2/11 (18.18)Female 6 – 11 months0/10 (0)0/12 (0)0/11 (0)0/10 (0)Female 1 year0/4 (0)0/4 (0)0/4 (0)0/4 (0)Female 2 – 8 years0/13 (0)0/13 (0)0/14 (0)0/13 (0)Female Intact1/18 (5.56)3/18 (16.67)0/17 (0)3/18 (16.67)Joint disorders. For ages 1 through 11 years and for each neuter period. Bold values indicate significance over intacts. Asterisk (*) shows significance using the Wilcoxon test: no significance with log-rank test. Dagger (†) indicates significance over intacts when the early groups are combined.LSAMCTHSAOSAAt Least OneMale < 6 months1/18 (5.56)0/18 (0)0/17 (0)0/18 (0)1/17 (5.88)Male 6 – 11 months1/28 (3.57)2/27 (7.41)0/27 (0)0/28 (0)3/27 (11.11)Male 1 year0/20 (0)1/21 (4.76)2/21 (9.52)0/21 (0)2/21 (9.52)Male 2 – 8 years1/36 (2.78)0/36 (0)0/34 (0)1/35 (2.86)2/33 (6.06)Male Intact4/84 (4.76)0/88 (0)2/87 (2.3)2/84 (2.38)8/81 (9.88)Female < 6 months1/12 (8.33)0/12 (0)0/12 (0)0/12 (0)1/12 (8.33)Female 6 – 11 months0/12 (0)0/11 (0)0/11 (0)0/12 (0)0/10 (0)Female 1 year0/4 (0)0/4 (0)0/4 (0)0/4 (0)0/4 (0)Female 2 – 8 years1/14 (7.14)1/14 (7.14)0/14 (0)0/14 (0)2/14 (14.29)Female Intact1/17 (5.88)0/17 (0)0/17 (0)0/17 (0)1/17 (5.88)Cancers. For ages 1 through 11 years and for each neuter period: no significant findings.

UI was only documented in females spayed under 6 months of age.

Summary: The Best Large Dog Spay & Neuter Times

Joint problems were more common in large dogs desexed under 1 year of age.

Recommendation: 1 year for both males and females.

This is so far the only science we have for the best desexing age in large breeds. Your vet, breeder or online group may have a different opinion based on their experience or personal beliefs. It’s perfectly reasonable to take their advice into consideration as well.

The decision may be based on other factors such as:

local neutering legislation
risk of male dog aggression to children
risk of pregnancy or reluctance to manage a female in heat
health problems associated with intact dogs

Problems With This Study

In the original paper, the authors appear to make some recommendations based on very limited evidence. I have published the original study data so you can see the actual numbers involved and decide for yourself.

The authors do not mention the well-known increase in lifespan associated with desexing male and female dogs, which tends to counteract most concerns about specific cancers.

The study tries to also look at the rates of mammary cancer & pyometra in females, but cannot give an accurate assessment for two reasons:

the mean ages listed above are far too young to pick up most cases
pyometra and mammary cancer are rarely referred to university hospitals

Regardless of any concerns, the authors are to be applauded to bringing into focus one of the most common questions from dog owners. For large breed dogs, they’ve made the decision a lot easier.

What happens if you neuter a large breed dog too early?

While some veterinary experts continue to recommend neutering earlier, others agree that large breeds may experience some health issues, including joint problems like knee injuries and hip dysplasia if neutered too early (prior to one year old).

Do male dogs get bigger after being neutered?

NOPE! Although, without some changes in behavior, it can happen. Spaying or neutering your dog or cat doesn't cause your pet to become overweight or obese. However, neutering is linked to an increased risk of weight gain if no change is made to what and how much you feed your pet after the surgery.

Do dogs get more aggressive after being neutered?

A: Yes, it's quite common for male dogs to experience an increase in aggression after being neutered. Neutering your male dog can also cause behavioral symptoms such as increases in fearful behavior, hyperarousal, and more.