When to Switch Puppy Food to Adult food for a Jack Russell Terrier?

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You already know that puppy food is quite different from adult dog food. As Jack Russell Terriers grow from puppies to adults, you must change their food to meet their nutritional needs.

To make a successful and safe diet transition for your dog, you must understand when to switch puppy food to adult food for a Jack Russell Terrier.

When to Switch Puppy Food to Adult Food for a Jack Russell Terrier

Once your JRT is 6-8 months old, switching your dog’s diet from puppy food to adult food is considered safe. Your dog has reached 80% of its expected adult size at this age. Depending on its genetics, your JRT may continue to grow in size up until they are about one year old.

Graphic image of dog food inside a bowl with a text explaining that after 6-8 months, Jack Russell Terriers should switch to adult food

As simple as it sounds, many aspects factor in when switching your dog from puppy food to adult dog food. As I discuss all the nutritional changes, how to undertake the process, and the risks involved, you’ll better grasp the best way to execute the food switch for your Jack Russell terrier.

Difference Between Puppy Food and Adult Dog Food

Most puppy food contains a minimum of 22% protein content and around 8% fat content to fuel puppies’ demanding cell growth rate. Adult dog food contains approximately 18% protein and 5% fat content, enough nutrients for a fully grown dog. Feeding puppy food to an adult dog and vice versa can put your dog at high health risks of conditions such as:

  • Malnutrition
  • Obesity
  • Nutritional Deficiency
  • Diabetes
  • Joint Issues
  • Heart Complications

For optimal growth, puppies require more protein and fat in their diet than adult dogs. At puppy age (up to 9 months), dogs have a higher metabolism and a faster growth rate. This metabolism and growth rate slows as your Jackie approaches ten months, which is around when you switch their diet.

Make the Switch Slowly

Slow and steady when switching up your Jack Russell Terriers diet is the way to go. A sudden diet change can trigger an upset in your pup’s digestive tract and result in vomiting, diarrhea, or hard stool. Terriers are picky and can reject the new food if you switch it up too quickly.

A person is pouring dog food from a glass bottle container into a white metal bowl on the brown floor

Most dog diet professionals recommend switching slowly within 7-10 days. However, this range can differ and take up to a month, per your veterinarian’s recommendation. Here’s an excellent example of a slow switch:

  1. Start by switching up 20% of the puppy food with adult food and mixing it up together
  2. Monitor your Jackie’s reception to the new food as well as its appetite
  3. Switch up 40% of the food after 1-2 days and blend it
  4. After three days, switch up to a higher ratio of 60% adult feed to puppy food
  5. Blend 80% adult dog feed with 20% puppy dog food after two days
  6. Finally, switch your Terrier to 100% adult feed now that they’ve become receptive to the new food

A slow switch will make it easy for you to monitor any reactions the new food may have to your JRT. Your dog will also get ample time to get used to the taste of the new food and begin to enjoy it.

Changes in Food Proportion and Frequency

JRT pups eat four servings of 2-3 ounces of puppy food daily. Cut down the feeding frequency to 3 times a day as your puppy approaches maturity. Maintain the same quantity of food given as before when you were administering four meal sessions.

When your dog hits the six-month mark, the feeding frequency changes to 2 meal times as you slowly switch to adult feed. Depending on the intensity of exercise and playtime your dog gets, you can hand out small snacks and treats in between days to replenish its energy, especially if you have a highly active Terrier.

Monitor the Weight of Your Jack Russell Terrier During the Switch

Many Jack Terrier owners fall victim to the common mistake of accidental overfeeding during the switch. Jack Russells are an active breed that relishes eating whatever amount of food you put in their bowl. If you keep refilling their bowl, they’ll keep eating.

Terrier owners need to monitor the weight of terriers during the switching period. You need to ensure you are reaching your dog’s nutritional needs without overfeeding or underfeeding it. Here’s a simple way to keep track of your dogs weight:

A person is pouring dog food from a brown paper bag into a white bowl with a black base held by another person
  1. Measure your weight on a scale and take note
  2. Pick up your dog, stand on the scales again and jot down the reading
  3. Subtract your weight from the total weight of you and your dog

It will be easy to monitor the weight progress of your pet if you keep a record and consistently measure your dog’s weight, possibly weekly or monthly.

Ideal Weight for Jack Russell Terriers

As your Jackie approaches the switching period (6-9 months), it should weigh close to 11 pounds. Once your dog’s a year old, its adult weight should stabilize at around 13 to 17 pounds. This weight can be affected by the food you feed your dog.

If you give them a poor-quality diet packed with artificial ingredients, they may need to eat more to hit the required nutritional mark. With high-quality feeds, you may require smaller portions. If you notice any drastic changes in this weight, consult your veterinarian to advise you on whether and how to adjust food portions correctly.

Ideal Body Condition of Jack Russell Terriers

If your Russell is beginning to look a bit like a sausage, there’s a slight chance it may be overweight. You should be able to notice a tuck where the abdomen slants upwards between the ribcage and hind legs. Likewise, you should be able to feel the ribs, pelvis, and backbone with a thin layer of fat.

Challenges You May Experience During the Switch

Russell Terriers are picky eaters. You may experience that your dog is reluctant to eat the new adult dog food or even refuse to eat it completely. To combat this situation, you must ensure the food is as fresh and tasty as possible.

You could try incorporating something tasty into the food to entice your dog to get used to the new food. In other cases, you may need to mix some wet food into the dry food to make it tastier. If your Russell completely refuses to eat despite your efforts, you may need to visit a veterinarian to check if anything’s up.

A portion of dog food is in a white and green plastic bowl with a dog's paws on a brown wooden floor


Jackies are a dog breed that is highly susceptible to allergic reactions from food. Some food may cause your dog to develop an itchy coat that your dog can damage as it tries to find relief through biting and scratching itself.

This itchy condition is known as Canine Atopic Dermatitis and can affect your pup, especially during the switch. It presents itself on the abdomen, ears, feet, and other areas. Coat itchiness is an evident food allergy, especially if accompanied by diarrhea or hardened stool.

Heart Conditions

Jack Terriers diagnosed with heart conditions require some vital nutrients in their food. These nutrients include L-Carnitine, Taurine, and Omega 3 Fatty acids, which are crucial to managing heart conditions.

Dogs with heart conditions require special care. If your pup has a heart condition, it would be best to consult your vet during the switch to ensure that your new feed meets the nutritional requirement for your dog.


Switching from puppy to adult food is one of the most standard and key processes when raising a dog. Providing your Jack Russell Terrier with plenty of water and a great deal of exercise during this switch makes for a happy, healthy pet. As usual, don’t hesitate to consult your veterinarian when in doubt.