Why Is My Pitbull So Small? Discover the Top 4 Key Factors You Need to Know!

1. Genetics and Breeding Background

The genetic makeup of your Pitbull is perhaps the most significant factor determining its size. This includes:

Parental genetics: If one or both parents were smaller Pitbulls, their offspring are likely to be smaller too
Breed mixture: Many “Pitbulls” are actually mixed with smaller breeds, resulting in smaller size
Specific breed type: Different Pitbull-type breeds have varying size standards:
- Staffordshire Bull Terriers are naturally smaller (14-16 inches)
- American Pit Bull Terriers tend to be medium-sized (17-21 inches)
- American Bullies can range significantly in size

2. Early Life Nutrition

Nutrition during the crucial growth phases can significantly impact adult size.

Inadequate caloric intake during puppyhood can lead to stunted growth
Poor-quality protein sources may not provide necessary amino acids for proper development
Imbalanced calcium and phosphorus levels can affect bone growth
Missing key nutrients during critical growth periods can limit size potential
Feeding schedule disruptions can impact overall growth

3. Health Factors

Various health conditions can influence your Pitbull’s size:

Parasitic infections during puppyhood can stunt growth
Hormonal imbalances affecting growth hormone production
Thyroid conditions impacting metabolism and growth
Early spaying/neutering can affect growth plate closure
Developmental issues affecting bone and muscle growth

4. Environmental Influences

The environment plays a crucial role in development.

Limited exercise during crucial growth periods
Stress or anxiety affecting eating habits and growth
Poor living conditions impacting overall development
Lack of proper veterinary care during growth phases
Insufficient sleep or rest affecting growth hormone production

Understanding Pitbull Breed Standards

What Defines a Pitbull?

Before delving into size issues, it’s crucial to know that “pitbull” is not really a single breed but rather a moniker used to describe multiple breeds, including:

American Pit Bull Terrier (APBT)
American Staffordshire Terrier (AmStaff)
Staffordshire Bull Terrier (Staffy)
American Bully

Each of these breeds has its own size standards and characteristics, which can lead to considerable variation in what’s considered “normal.”

Standard Size Ranges

Here’s a comprehensive breakdown of standard size ranges for different Pitbull-type breeds:

Breed Type	Height (Males)	Height (Females)	Weight (Males)	Weight (Females)
American Pit Bull Terrier	18-21 inches	17-20 inches	35-60 lbs	30-50 lbs
American Staffordshire Terrier	18-19 inches	17-18 inches	55-70 lbs	40-55 lbs
Staffordshire Bull Terrier	14-16 inches	13-15 inches	28-38 lbs	24-34 lbs
American Bully (Standard)	17-20 inches	16-19 inches	50-120 lbs	40-100 lbs

Genetic Factors Affecting Size

Inherited Traits

The size of your Pitbull is fundamentally governed by genetics, with several complex mechanisms at work:

Parental Genetics and Size: The physical characteristics of parent dogs serve as a primary predictor of offspring size. Puppies usually grow to be within the range of their parents’ sizes, following simple hereditary patterns. For instance, there is a great chance their offspring will likewise be smaller if both parent dogs fall on the smaller side of breed standards. This results from several genes inherited controlling muscle mass, bone development, and growth hormones.

Breed-specific Genetic Markers: Pitbulls possess distinct genetic markers that influence their physical development:

Growth hormone receptor genes that regulate size development
IGF-1 (Insulin-like Growth Factor 1) variants that affect overall body size
Specific alleles responsible for muscle mass development
Genetic sequences controlling bone density and structure
DNA markers associated with height and weight potential

Gene Expression Patterns: The way genes are expressed can significantly impact a Pitbull’s size:

Epigenetic factors can activate or suppress growth-related genes
Environmental conditions can influence gene expression
Hormonal balances affect how size-related genes are expressed
Timing of gene activation during development stages
Interaction between different genetic pathways

Genetic Diversity Within Bloodlines: The variety within breeding lines affects size potential:

Inbred lines may show more consistent but potentially smaller sizes
Diverse bloodlines often produce more varied size ranges
Historical breeding selections impact modern size genetics
Genetic bottlenecks can limit size potential
Hybrid vigor from diverse genetics can influence growth

Presence of Dwarfism Genes or Size-Affecting Mutations: Specific genetic variations can dramatically impact size:

Chondrodysplasia genes affecting bone growth
Growth hormone deficiency mutations
Thyroid hormone receptor mutations
Skeletal development gene variations
Muscle development genetic factors

Mixed Breeding Impact

The introduction of other breeds into the Pitbull genetic pool creates significant size variations:

Mixing with Smaller Breeds: When Pitbulls are bred with smaller dogs, the resulting offspring often show:

Reduced overall body size compared to purebred standards
Different body proportions than typical Pitbulls
Varied muscle mass development patterns
Modified bone structure and density
Altered growth rates during development

Historical Breeding Practices: Past breeding decisions continue to influence modern Pitbulls:

Early 20th-century selection for smaller, more agile dogs
Regional variations in preferred size standards
Working dog vs. companion dog breeding goals
Show ring influences on breed development
Impact of breed recognition standards on size selection

Generation-to-Generation Size Inheritance: Size traits pass through generations in complex patterns:

Dominant and recessive gene interactions
Multigenerational size trend developments
Impact of selective breeding on size stability
Influence of outcrossing on size predictability
Expression of ancestral size traits

Genetic Diversity Benefits and Drawbacks: Mixed breeding creates both advantages and challenges:

Benefits:

Reduced risk of genetic health issues
Improved adaptability to environmental conditions
Enhanced immune system function
Better overall genetic resilience
Potential for improved longevity

Drawbacks:

Less predictable adult size
Inconsistent growth patterns
Variable physical characteristics
Challenging breed standard conformity
Potential loss of desired breed traits

Environmental Factors

Nutrition and Growth

Proper nutrition during critical developmental stages significantly influences your Pitbull’s ultimate size and health:

Quality of Puppy Food During Developmental Stages:

Premium puppy formulas contain optimal nutrient ratios for growth
High-quality protein sources ensure proper muscle development
Essential fatty acids support brain and tissue development
Micronutrients play crucial roles in bone formation
Growth-specific formulas account for rapid development needs

Protein and Calcium Intake: Proper protein levels are essential for growth.

Puppies need 22–32% protein content in their diet
Quality protein sources include chicken, fish, and lamb
Essential amino acids support muscle development
Calcium intake should be 1.2-1.8% of diet for puppies
Calcium-to-phosphorus ratio should be 1.2:1 to 1.4:1

Balanced Nutrition Requirements: A well-balanced diet includes:

Appropriate carbohydrate levels for energy
Essential fatty acids for brain development
Vitamins A, D, E, and K for proper growth
Mineral balance for bone development
Adequate fiber for digestive health

Feeding Schedule and Portion Control: Proper timing and amounts are crucial.

3-4 meals daily for puppies under 6 months
Gradual transition to 2-3 meals daily
Portion sizes based on projected adult weight
Regular feeding times to maintain metabolism
Monitoring growth rates to adjust portions

Supplementation Needs: Careful consideration of supplements:

Joint supplements for growing puppies
Omega-3 fatty acids for brain development
Vitamin D for proper bone growth
Probiotics for digestive health
Additional supplements only as veterinary-recommended

Living Conditions

Environmental factors play a significant role in physical development:

Exercise Opportunities and Limitations: Physical activity impacts growth.

Appropriate exercise for developmental stages
Avoiding over-exercise during growth periods
Balanced cardio and strength activities
Safe play environments for development
Structured exercise routines for optimal growth

Living Space Restrictions: Living environment affects development:

Adequate space for movement and play
Safe flooring for joint development
Access to outdoor areas
Temperature-controlled environments
Appropriate sleeping arrangements

Climate and Temperature Effects: Environmental conditions influence growth:

Temperature impact on metabolism
Seasonal activity level variations
Humidity effects on exercise tolerance
Weather-appropriate exercise scheduling
Indoor/outdoor balance based on climate

Stress Levels and Mental Health: Psychological factors affect physical development:

Stress hormone impacts on growth
Anxiety effects on eating patterns
Sleep quality influences development
Environmental stability importance
Routine consistency for optimal growth

Social Interaction and Stimulation: Social factors contribute to development

Interaction with other dogs
Human socialization opportunities
Mental stimulation through play
Training activities for growth
Environmental enrichment practices

Additional Environmental Considerations:

Living Space Quality:

Clean and hygienic conditions
Proper ventilation
Appropriate lighting
Safe and secure boundaries
Comfortable resting areas

Daily Routine Stability:

Consistent feeding times
Regular exercise schedule
Structured rest periods
Predictable social interactions
Balanced activity levels

Environmental Enrichment:

Age-appropriate toys
Learning opportunities
Sensory experiences
Social encounters
Physical challenges

Safety Considerations:

Puppy-proofed environment
Appropriate exercise equipment
Safe play areas
Temperature regulation
Proper supervision

Health Monitoring:

Regular weight checks
Growth rate tracking
Activity level monitoring
Behavioral observation
Health symptom awareness

Health-Related Size Factors

Medical Conditions

Various health issues can significantly impact a Pitbull’s growth and final size:

Hormonal Imbalances: Growth hormone deficiencies can severely affect size:

Insufficient growth hormone production by the pituitary gland
Insulin-like growth factor 1 (IGF-1) deficiencies
Cortisol imbalances affecting metabolism
Sex hormone irregularities impacting development
Pituitary gland dysfunction affecting multiple hormones

Thyroid Disorders: Thyroid conditions impact growth and development:

Hypothyroidism slows metabolic rate and growth
Hyperthyroidism causing excessive metabolism
Thyroid hormone imbalances affecting bone development
Impact on protein synthesis and muscle growth
Metabolic rate fluctuations affecting nutrient utilization

Growth Plate Injuries: Damage to growth plates can alter development.

Trauma-induced growth plate closure
Uneven growth due to partial plate damage
Long bone development issues
Joint alignment problems
Recovery complications affecting final size

Parasite Infections: Parasites can interfere with growth.

Intestinal worms competing for nutrients
Giardia affecting nutrient absorption
Coccidia impacting gut health
Hookworms causing anemia and stunted growth
Long-term effects of early parasite exposure

Digestive Disorders: Gastrointestinal issues affect nutrient absorption.

Inflammatory bowel disease
Malabsorption syndromes
Chronic diarrhea effects
Food sensitivity impacts
Gut flora imbalances

Developmental Issues

Various factors can impact normal growth and development:

Early Spaying/Neutering: Timing of alteration affects growth:

Impact on growth plate closure timing
Hormonal changes affecting bone density
Muscle mass development differences
Body composition changes
Long-term skeletal effects

Vaccination Timing: Proper vaccination scheduling is crucial.

Immune system development impact
Stress on growing body
Recovery periods affecting growth
Vaccination reaction considerations
Overall health impact during growth phases

Bone Development Problems: Skeletal issues affecting growth:

Hip dysplasia impact
Osteochondritis dissecans
Panosteitis during growth
Calcium metabolism issues
Bone density concerns

Muscle Mass Development: Factors affecting muscular growth:

Protein synthesis efficiency
Exercise impact on muscle development
Nutritional factors in muscle growth
Hormonal influences on muscle mass
Genetic factors in muscle development

Growth Plate Closure Timing: Critical developmental milestones:

Normal closure ranges (12-18 months)
Factors affecting closure timing
Impact of early/late closure
Growth rate variations
Final size implications

Additional Health Considerations:

Metabolic Issues:

Enzyme deficiencies
Metabolic rate abnormalities
Nutrient processing problems
Energy utilization issues
Growth rate irregularities

Immune System Health:

Autoimmune conditions
Chronic inflammation effects
Infection susceptibility
Recovery capacity
Overall immune function

Neurological Factors:

Brain development impact
Nerve signal transmission
Motor function development
Coordination issues
Growth regulation

Cardiovascular Health:

Blood flow efficiency
Oxygen delivery to tissues
Exercise tolerance
Recovery capacity
Overall fitness level

Environmental Stress Response:

Cortisol levels
Stress impact on growth
Recovery from illness
Adaptation ability
Long-term health effects

Understanding these health-related factors is crucial for:

Early detection of growth issues
Appropriate veterinary intervention
Preventive health measures
Growth monitoring strategies
Long-term health management

Nutritional Considerations

Dietary Requirements

Protein Requirements (23-30% for puppies):

High-quality protein sources essential for muscle development:
- Chicken, turkey, and fish as primary proteins
- Lamb and beef as alternative sources
- Egg protein for additional amino acids
- Plant-based proteins as supplements
- Protein digestibility considerations

Fat Content Needs (12-18%): Essential fats for growth and development:

Omega-3 fatty acids for brain development
Omega-6 fatty acids for skin and coat health
DHA requirements for cognitive function
EPA for anti-inflammatory benefits
Balanced fat ratios for optimal absorption

Essential Minerals and Vitamins: Key nutrients for proper growth:

Calcium (1.2-1.8% for puppies)
Phosphorus in proper ratios
Zinc for immune system function
Iron for blood health
Vitamins A, D, E, and K

Water Intake Importance: Proper Hydration Guidelines:

1 ounce of water per pound of body weight daily
Increased needs during growth spurts
Additional requirements during exercise
Climate-based adjustments
Monitoring hydration levels

Meal Frequency Recommendations: Age-appropriate feeding schedules:

4 meals daily (8-12 weeks)
3 meals daily (3-6 months)
2 meals daily (6+ months)
Portion size calculations
Timing between meals

Common Nutritional Mistakes

Overfeeding or Underfeeding: Impact on growth and development:

Caloric intake calculations
Growth rate monitoring
Body condition scoring
Weight tracking importance
Adjusting portions appropriately

Poor Quality Food Choices: Understanding food quality:

Reading ingredient labels
Avoiding fillers and by-products
Identifying quality protein sources
Checking for artificial preservatives
Understanding nutritional standards

Inconsistent Feeding Schedules: Effects of irregular feeding:

Metabolic impact
Digestive issues
Growth pattern disruption
Behavioral problems
Energy level fluctuations

Improper Supplementation: Common supplementation errors:

Over-supplementation risks
Calcium/phosphorus imbalances
Vitamin excess concerns
Mineral interaction issues
Unnecessary supplement use

Ignoring Age-specific Nutritional Needs: Life stage considerations:

Puppy-specific requirements
Growth phase adjustments
Activity level matching
Health condition adaptations
Senior dog transitions

Additional Nutritional Considerations:

Food Safety and Storage:

Proper storage temperatures
Freshness monitoring
Container requirements
Expiration date tracking
Contamination prevention

Transitioning Foods:

Gradual food changes
Monitoring digestive response
Mixing ratios
Timing considerations
Health observation

Special Dietary Needs:

Food sensitivities
Allergies management
Medical condition diets
Weight management
Performance requirements

Feeding Environment:

Quiet feeding location
Clean feeding areas
Appropriate bowls
Feeding height
Stress-free environment

Monitoring and Adjustment:

Regular weight checks
Growth rate tracking
Body condition scoring
Energy level assessment
Health indicator monitoring

Key Guidelines for Optimal Nutrition:

Quality Control:

Choose AAFCO-approved foods
Verify ingredient quality
Check manufacturing standards
Research brand reputation
Review recall history

Portion Control:

Use measuring tools
Follow feeding guidelines
Adjust for activity level
Monitor body condition
Consider treat calories

Schedule Management:

Consistent feeding times
Appropriate meal spacing
Exercise timing
Rest periods
Treat timing

Health Integration:

Veterinary consultation
Growth monitoring
Health assessment
Dietary adjustments
Supplement evaluation

Documentation:

Food intake tracking
Weight monitoring
Growth progression
Health observations
Dietary changes

Exercise and Physical Development

Appropriate Exercise Levels

Age-appropriate Activity Levels: Exercise requirements by age:

8-12 weeks: 15-20 minutes, 2-3 times daily
- Short play sessions
- Basic socialization activities
- Gentle exploration time
- Supervised yard play
- Brief training exercises
3-6 months: 20-30 minutes, 2-3 times daily
- Structured play sessions
- Basic obedience training
- Controlled walking
- Interactive games
- Mental stimulation activities
6-12 months: 30-45 minutes, 2-3 times daily
- Longer walks
- Increased play intensity
- Advanced training
- Controlled running
- Agility introductions

Strength Training Considerations: Natural strength development activities:

Controlled tug-of-war games
Appropriate chew toys for jaw strength
Low-impact climbing activities
Balance exercises
Body weight resistance activities

Cardio Exercise Requirements: Cardiovascular development guidelines:

Progressive intensity increases
Heart rate monitoring
Endurance building activities
Recovery period observation
Weather-appropriate scheduling

Rest and Recovery Importance: Essential recovery guidelines:

Sleep requirements (18-20 hours for puppies)
Post-exercise cooling down
Quiet time between activities
Growth phase rest periods
Signs of exercise fatigue

Joint Health Protection: Preventive measures:

Low-impact exercise selection
Proper surface choices
Avoiding repetitive movements
Monitoring for strain signs
Joint supplement considerations

Impact on Growth

Muscle Mass Building: Proper muscle development through:

Progressive resistance activities
Balanced muscle group exercise
Natural movement patterns
Growth phase-appropriate activities
Recovery time for muscle development

Bone Density Improvement: Factors affecting bone strength:

Weight-bearing exercise benefits
Impact level considerations
Exercise duration effects
Growth plate protection
Calcium utilization during activity

Metabolic Rate Regulation: Exercise impact on metabolism:

Activity level effects
Energy expenditure balance
Growth phase considerations
Nutrient utilization
Recovery period metabolism

Growth Plate Protection: Safety considerations:

Exercise timing during growth
Impact level monitoring
Surface type selection
Duration limitations
Recovery period importance

Overall Body Composition: Development factors:

Muscle-to-fat ratio
Skeletal development support
Tissue development balance
Growth pattern influence
Long-term composition effects

Additional Exercise Considerations:

Environmental Factors:

Temperature considerations
Surface types
Space requirements
Safety measures
Weather adaptations

Exercise Types:

Structured activities
- Leashed walks
- Training sessions
- Controlled play
- Swimming
- Basic agility
Free play activities
- Yard exploration
- Social play
- Toy interaction
- Chase games
- Natural movement

Exercise Safety:

Warning signs of overexertion:
- Excessive panting
- Reluctance to move
- Limping
- Lethargy
- Behavioral changes

Mental Stimulation:

Training exercises
Problem-solving activities
Socialization opportunities
Environmental enrichment
Interactive play

Growth Phase Monitoring:

Regular vet check-ups
Growth rate tracking
Exercise adjustment needs
Development milestone monitoring
Health indicator observation

Key Guidelines for Exercise Management:

Progressive Development:

Gradual intensity increases
Skill building sequence
Endurance development
Strength progression
Coordination improvement

Safety Protocols:

Warm-up activities
Cool-down periods
Surface assessment
Weather considerations
Equipment safety

Exercise Scheduling:

Daily routine planning
Rest period allocation
Activity variety
Energy level matching
Growth phase consideration

Monitoring Systems:

Exercise tracking
Recovery observation
Development progress
Health indicators
Behavior patterns

When to Be Concerned

Red Flags

Significant Size Difference from Breed Standards: Key indicators of concerning size variations:

More than 20% below breed standard weight
Height significantly under expected range
Disproportionate body measurements
Unusual growth rate patterns
Comparative size to littermates

Specific measurement concerns:

Adult male under 35 lbs (APBT standard)
Adult female under 30 lbs (APBT standard)
Height more than 2 inches below standard
Severely delayed growth milestones
Abnormal body proportions

Stunted Growth Patterns: Identifying problematic growth:

Extended periods without weight gain
Minimal height increases during growth phases
Uneven or asymmetrical development
Delayed physical maturity signs
Growth plate abnormalities

Growth rate concerns:

Less than 2-3 lbs gain per week (young puppies)
Plateau in growth before maturity
Irregular growth spurts
Failure to meet developmental milestones
Comparative growth charts deviation

Visible Health Issues: Physical symptoms to monitor:

Coat quality changes
- Dull or brittle fur
- Excessive shedding
- Bald patches
- Skin problems
- Poor coat texture
Structural concerns
- Bow-legged appearance
- Joint swelling
- Limping or gait issues
- Spine irregularities
- Muscle wastage

Behavioural Changes: Concerning behavioural indicators:

Lethargy or decreased activity
Excessive sleeping beyond normal puppy needs
Reduced play drive
Social withdrawal
Exercise intolerance

Activity-related concerns:

Reluctance to move or exercise
Difficulty getting up after rest
Pain signs during movement
Decreased stamina
Unusual posturing

Appetite Fluctuations: Eating pattern concerns:

Complete loss of appetite
Excessive hunger
Difficulty maintaining weight
Unusual food preferences
Digestive issues

Professional Assessment

Growth rates are abnormal. When to seek immediate veterinary attention:

No weight gain for 2+ weeks
Rapid unexplained weight loss
Dramatic growth spurts
Severely delayed growth
Asymmetrical development

Physical development is delayed. Development concerns requiring assessment:

Delayed teething
Poor muscle development
Bone growth abnormalities
Joint development issues
Organ maturation concerns

Health Symptoms Appear: Critical health indicators:

Chronic diarrhea or vomiting
Respiratory issues
Skin conditions
Joint swelling
Neurological symptoms

Feeding Issues Persist: Ongoing nutritional concerns

Consistent food refusal
Difficulty swallowing
Excessive water consumption
Frequent regurgitation
Unusual eating behaviors

Behavioural Concerns Arise: Behavioural changes requiring attention:

Aggression development
Excessive fearfulness
Chronic anxiety
Depression symptoms
Cognitive issues

Additional Assessment Considerations:

Testing and Diagnostics:

Blood work panels
Growth hormone testing
Thyroid function assessment
X-rays for bone development
Genetic testing when indicated

Documentation Needs:

Growth charts
Feeding records
Behavior logs
Exercise journals
Health incident tracking

Follow-up Care:

Regular monitoring schedules
Treatment plan adherence
Progress evaluation
Adjustment protocols
Long-term management

Prevention Strategies:

Nutritional optimization
Exercise modification
Environmental adjustments
Health maintenance
Stress reduction

Support Systems:

Veterinary team coordination
Specialist referrals
Behavioral support
Nutritional guidance
Owner education

FAQ Section

Can Pitbulls stay small?

Usually medium-sized dogs, Pitbulls weigh between thirty and 70 pounds. By intentionally mating smaller individuals, some breeders do nevertheless provide “mini” or “pocket” Pitbulls. Although these dogs have the Pitbull qualities, it’s crucial to guarantee moral breeding methods to prevent problems with health. Essential are training and good care.

Why is my pitbull not getting bigger?

Possible causes for your Pitbull’s stunted growth include hereditary factors, poor nutrition, or health problems. Make sure they visit the vet frequently and consume a healthy diet. The genetic makeup of some Pitbulls makes them smaller than average. Get your pet checked out by a vet if you’re worried about any health issues.

Why is my pit bull so skinny?

A skinny Pitbull could be underweight from bad food, parasites, stress, or an underlying illness. Make sure they are getting consistent veterinarian visits and a healthy diet. Illnesses, including intestinal worms, can influence weight. See your veterinarian for a comprehensive check and customised guidance if diet changes and deworming prove insufficient.

At what age is a pitbull fully grown?

Usually reaching full physical development between 18 months and two years of age, pitbulls They keep building muscle and completing their adult frame during this time. Genes, food, and general health can all affect growth rates. Frequent veterinarian visits guarantee they are developing at a reasonable rate.

What is the smallest type of pitbull?

Often called the “Pocket Pitbull” or “Miniature Pitbull, the tiniest kind of Pitbull is Combining the Patterdale Terrier with the American Pitbull Terrier. These dogs usually stand around 12–16 inches tall and weigh between 30 and 60 pounds. Their diminutive stature notwithstanding, they have the usual Pitbull traits.

How big is a 1 year old pitbull?

Depending on genes and diet, a one-year-old Pitbull usually stands 18 to 21 inches tall and weighs between 35 and 60 pounds. Though they may still be developing muscular mass and filling out, by this age they are almost fully physically mature. Frequent veterinarian visits guarantee they are keeping a balanced weight and growing properly.

Conclusion

A smaller Pitbull does not always point to any issues with your cherished animal. Many of the elements that affect a dog’s growth are quite natural and healthy, as we have seen throughout this page. Regardless of their size, the most crucial things are making sure your Pitbull has regular veterinary care, enough exercise, and an appropriate diet. Every dog is different; hence, size shouldn’t be a big issue as long as your pet is healthy, active, and content. Emphasise giving your dog the finest treatment and appreciating its unique traits.

Additional Resources

American Kennel Club (AKC) Breed Standards: www.akc.org/dog-breeds/
United Kennel Club (UKC) Breed Information: www.ukcdogs.com/breed-standards
American Veterinary Medical Association (AVMA): www.avma.org/resources/pet-owners/petcare
PetMD Dog Nutrition Center: www.petmd.com/dog/nutrition
Association of American Feed Control Officials (AAFCO): www.aafco.org/