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Why Is My Border Collie So Small? (The 4 Main Reasons)

When you frequently see other Border Collies that appear to be bigger than yours, it’s normal to wonder why. This article explains why some Border Collies end up being smaller than others, and what you can do about it.


How Big Should a Border Collie Be?

The AKC acknowledges Border Collies as a medium-sized herding dog that is both muscular and also “nimble”. Let’s take a look at the average height and weight ranges for adult Collies.

MALE Average height and weight:
Height: 19-22 Inches
Weight: 40-55 Pounds

FEMALE Average height and weight:
Height: 18-21 Inches
Weight: 30-45 Pounds

Most Border Collies fall within the above height and weight averages, but, even still, it’s normal for some collies to be on either side of the ranges.

Also, note that this is for adult Border Collies. Most of the time, their full height is reached by around 10-12 months. So if your collie is still under 1 year, she may still have some growing to do. Overall weight gain usually carries on until around 2 years old.

4 Reasons Why Your Border Collie Is Small

If your Border Collie is on the small side, let’s run through the most likely reasons why.

1. Genetics

Something to consider first and foremost is genetics. Physical traits pass down to the offspring, more so than behavioral traits.

This means if the parents of your Border Collie were both smaller than average, it’s very likely that your Collie will also be on the small side.

It’s also worth confirming the blood lineage of your Collie. If there has been cross-breeding in previous generations, this may result in a more varied size range for your Border Collie.


You guessed it, there’s not much you have control over when it comes to genetics. If your Border Collie is destined to be on the small side due to genes, nothing can be done about it.

Trying to find out information about the parents of any dog is a difficult task, especially as more time passes since bringing her home. If you have contact information for your breeder, give them a call and they may be able to provide some information on the parents. It’s worth a try.

If your collie is a rescue, you won’t be able to find this kind of information out.

2. Diet and Eating Habits

Diet and eating habits are the next most essential thing that can affect the size of your Border Collie.

To start with, if your Border Collie has a habit of leaving her food, her overall calorie consumption may not be sufficient. Without enough protein, fat, carbs (calories) your collie’s growth and development can suffer. This is particularly true while she’s still a puppy (under 1 year).

The next consideration is quality. The quality of the diet she’s on will affect also affect her growth and development. The brand you use has a big effect on the nutritional breakdown and the quality of the ingredients used.

It’s always recommended to use premium brands because the quality of the ingredients is just far better. This means fresher and more wholesome, without by-products, fillers, artificial preservatives, flavorings, colors, and additives. Better ingredients mean better nutrition and absorption into the body.

Premium brands also tend to contain more favorable macronutrient breakdowns. This means a higher protein and fat content compared to carbs. This breakdown mimics what a wild diet would have been like, and therefore works better for nearly all dogs. A better diet means better growth, development, and health.


It’s advised to simply observe your Border Collie over the next few mealtimes. This will show you if she leaves her food, if she feels bad afterward, or if she actually enjoys it. After doing so, consider the following points:

Portion size: Ensure her portion sizes and calorie consumption is correct for her age and current weight. Although this is more important to get right while she’s a pup, it still does matter when she’s an adult. She needs to be consuming enough calories.

Use a premium brand: Premium brands are more expensive for a few good reasons. Their ingredients are fresher, wholesome, and better quality, meaning they will absorb into the body more entirely than cheap brands with lower quality ingredients. Premium brands also tend to have a higher protein and fat content, which not only mimics a wild diet but contains more calories for the same amount of food.

Introduce 80% dry kibble with 20% wet dog food: This has long been recommended by veterinarians. Instead of feeding her all dry kibble, take some out and add in some wet dog food instead. Wet dog food is far more nutritious than dry kibble, it’s tastier, higher in protein, and will encourage her to finish her entire meals.

Stick to feeding times: This one is to prevent unfinished meals. Creating and sticking to set mealtimes is important. And if you aren’t already doing this, you need to start. By sticking to routine times, your Border Collie is essentially learning to be hungry at those times. This helps to build an appetite and avoids leftovers.

Time-restricted eating: If your collie is still being fussy, the next thing to try is time-restricted eating. This involves putting her food bowl down for 10 minutes before removing it. This will certainly test your morals, but it’s designed to teach your dog that she needs to eat her meals when you give it to her.

After the first removal, by the next mealtime, her survival instincts would have kicked in, and she’ll be eager to eat her meal immediately. Many people have success after the first removal, and it has been known to cure bad eating habits for up to several months afterward. Always give fresh kibble, and never remove more than two consecutive meals.

3. Over-Exercising

Border Collies are a hard-working breed known to require a lot of daily exercise. Around 1 to 2 hours per day is the range, depending on their age and health.

If you’re currently pushing the limit with her exercise and are around the 2-hour mark (or even over) then try reeling back her exercise. This will allow her body to rest and recover more, as well as burning fewer calories.

Exercise becomes even more of an issue if your Border Collie is still a puppy (Under 1 year). Puppies grow while they rest, and that’s one of the reasons why they sleep up to 18 hours per day!

Over-exercising a puppy can put too much stress on their premature bones, joints, and ligaments. Not only can this interfere with proper growth and development, but too much exercise will likely be burning too many calories.


Follow the 5-minute method: This involves exercising your puppy for 5 minutes per day, per month of age they have. So 3 months = 15 minutes per day, 4 months = 20 minutes per day. This rule was designed to ensure you do not over-exercise your puppy. This excludes playtime.

4. Health Issues

In more unfortunate situations, your Border Collie may be smaller due to an underlying health condition.

This may have been present during puppyhood and had an effect on her growth and development, or it may be something that’s still currently an issue.

Health concerns can only be ruled out by visiting your veterinarian and having a complete health check-up done.

There is a wide range of health issues that do in fact hinder growth, proper weight gain, or becoming frail. The best thing to do is to schedule a check-up.

Why Is My Border Collie Skinny?

There’s a distinction that should be noted between being skinny and small. If your Border Collie looks skinny, this is a different issue than being “small”. Small refers mostly to height and overall build, skinny is refers to body weight.

If your Collie is significantly underweight then this issue should be dealt with as soon as possible and a check-up with your veterinarian is advised.

For reference, the average weight ranges for male and female Border Collies:

  • The average weight for males is 40-55 lbs
  • The average weight for females is 30-45 lbs

As explained above, if your Border Collie is still a puppy, it’s essential that you are not over-exercising her. She should also be on a premium kibble that’s formulated for puppies. All life stage formulas do not provide adequate nutrition or calories for puppies.

If you are unsure as to why your collie is underweight, the best thing you can do is schedule an appointment with your veterinarian. You can rule out health concerns and get a professional opinion.

Is Your Border Collie Happy and Healthy?

Even if your Border Collie is on the small side, as long as she’s happy and healthy, that’s all that matters!

There will always be dogs who are a little over or under their normal breed specifications, and it’s completely normal.

It’s essential to rule out health conditions so you know she is healthy, then after that, it’s just a matter of providing her the best life you can.

The most important things to consider is the quality of her diet and how well she gets on with her diet, her exercise routine, training, and her home life. Sometimes, size just doesn’t matter!

Border Collie Articles:
Do Border Collies Smell? Reasons Why Yours Might
The KEY Differences Between Male & Female Border Collies

Final Thoughts

So there you have it! You now know the four main reasons behind a smaller-than-average Border Collie: Genetics, her diet and eating habits, being over-exercised (especially as a puppy), or due to health concerns.

And remember, being on the small side doesn’t mean she can’t live a healthy and happy life! Just be sure to rule out any concerns with your veterinarian.

View all Border Collie articles >>

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Before making any decisions that could affect the health and/or safety of your dog, you should always consult a trained veterinarian in your local area. Even though this content may have been written/reviewed by a trained veterinarian, our advice to you is to always consult your own local veterinarian in person. Please read our full dislcaimer if you have any questions.