Kittens are typically weaned off of their mother's milk at about 8 weeks of age and become reliant on pet owners for their nutrition. 
The goal of feeding growing kittens is to lay the foundation for a healthy adulthood. Proper nutrition is needed to:
- achieve healthy growth (neither too rapid nor too slow),
- optimize immune function, and
- minimize potential for obesity.
What does normal growth and development look like?
Kittens grow quickly, maturing to adulthood by the time they are 10-12 months of age. Their growth rate slows as they approach 80% of adult size at about 30 weeks of age, and they reach adult body size at about 40 weeks of age.
Growth rates for kittens vary by breed and involve a complex process of interactions among genetics, nutrition, and the environment. Proper nutrition is critical to the health and development of kittens, regardless of breed, and it directly influences their immune system and body composition. The nutrient density of food and the amount of food fed can mean the difference between optimal growth and maximal growth.
Should I aim for optimal growth or maximal growth?
An optimal growth rate in kittens is ideal; it is a slow and steady growth rate that allows the kitten to achieve an ideal (optimal) adult body condition while avoiding excessive weight and obesity.
The maximal growth rate means the kitten grows as fast as possible, usually the result of high fat foods, overfeeding and/ or free-choice feeding. A maximal growth rate can increase a kitten's risk of becoming overweight or obese.
Regular weigh-ins and body condition assessments are the most practical strategies to help keep a growing kitten on track at an optimal rate. Your veterinarian and veterinary healthcare team can explain how to assess your kitten at home.
What are the nutritional requirements for a growing kitten?
When choosing a diet for your growing kitten, it is important to understand three key nutrients: protein, fat, and calcium.
Protein
- Protein requirements for growing kittens are high during the weaning stage, but the amount of protein they need will steadily decrease thereafter.
- The recommended protein range for healthy kitten growth is 35-50% on a dry matter basis with at least 9% dry matter from an animal source. These levels support optimal growth, so it is not recommended to exceed them.
- Nutritional formulations for adult cats should not be fed to growing kittens. Although the dry matter protein level may be adequate, other nutrients and energy content will not be balanced for optimal growth.
Fat
- Fat is a source of essential fatty acids. It is a concentrated source of energy and it carries fat-soluble vitamins.
- Excessive energy intake is risky and can lead to obesity and developmental orthopedic disease. For this reason, the fat content for kittens should be rationed between 18-35% on a dry matter basis.
Calcium
- Kitten growth formulations should contain 0.8-1.6% calcium on a dry matter basis.
Once an appropriate nutritional product has been chosen, no additional vitamin or mineral supplements should be given. You should also avoid foods that produce a urinary pH of less than 6.2. Your veterinarian can help you determine the pH levels for kitten foods you are considering.
How can I prevent maximal growth and obesity?
Growing kittens need higher amounts of all nutrients in comparison to adult cats, but excess energy calories and calcium can create serious problems. Preventing obesity must begin during the weaning stage and continue through to adulthood and old age. Being overweight or obese sets the stage for many complications and diseases, including:
- hypertension
- heart disease
- diabetes mellitus
- osteoarthritis
- heat intolerance
- decreased immune function
Free-choice feeding increases the risks for higher levels of body fat and becoming overweight or obese. Portion feeding provides the greatest opportunity to prevent kittens from becoming overweight or obese - they do best when their total daily portion of food is offered in 3-4 small meals or more each day. Also note that dry foods are more calorie-dense than canned foods, and canned foods tend to be more tasty than dry.
"Free-choice feeding increases the risks for higher levels of body fat and becoming overweight or obese."
With planning and attention to detail, you can lay the foundation for your kitten's optimal health and longevity. Together with your veterinarian and veterinary healthcare team, you can help your kitten grow into as healthy of an adult cat as possible.
