Participants will receive stage 1 formulas up to 180 days of age and then switch to stage 2 formulas though 365 days of age.

Exclusively breastfed for the first 4 months and continue with supplement food without any marketed infant formula.

Motor Scale of Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) is used to evaluate the infant motor skills at 365 days of age.

1. Unabbreviated scale title：Bayley-III Scales of Infant Development Tables and Graphs Report-- Motor Scale
2. Bayley-III contains two scoring systems of composite scores and percentile ranks. The normal range for composite scores is between 40-160 with mean at 100 and 0-99 for the percentile ranks.
3. Higher scores mean a better outcome.

Social-emotional Scale of Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) is used to evaluate the infant social-emotional capabilities at 365 days of age.

1. Unabbreviated scale title：Bayley-III Scales of Infant Development Tables and Graphs Report-- Social-emotional Scale.
2. Bayley-III contains two scoring systems of composite scores and percentile ranks. The normal range for composite scores is between 40-160 with mean at 100 and 0-99 for the percentile ranks.
3. Higher scores mean a better outcome.

Adaptive behavior Scale of Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) is used as the infant adaptive behavior assessment tool at 365 days of age.

1. Unabbreviated scale title：Bayley-III Scales of Infant Development Tables and Graphs Report-- Adaptive behavior scale
2. Bayley-III contains two scoring systems of composite scores and percentile ranks. The normal range for composite scores is between 40-160 with mean at 100 and 0-99 for the percentile ranks.
3. Higher scores mean a better outcome.

Ages and Stages Questionnaires (ASQ) is administered at 120, 180, and 275 days of age.

ASQ is a developmental screening system comprised of age-specific questionnaires which measure 5 domains of infant development.

1. Unabbreviated scale title： Ages and Stages Questionnaires；
2. the minimum~maximum value：0~60 points；
3. Higher scores mean a better outcome.

MacArthur-Bates Communicative Development Inventory (CDI) tests is administered at 365 days of age.

It is a parent-report measure that has been validated against actual child language diaries.

1. Unabbreviated scale title：MacArthur-Bates Communicative Development Inventory evaluation form
2. the minimum~maximum percentile：5%-99%；
3. The higher the percentile, the better；

Carey Toddler Temperament Scale (TTS) tests is administered at 365 days of age. TTS is a 97-item questionnaire which measures the nine categories of temperament: activity level, regularity, adaptability, approach-withdrawal, intensity, mood, persistence, sensory threshold and distractibility.

1. Unabbreviated scale title：Carey Toddler Temperament Scale

2. Normal score range of TTS for 1 to 3 year old infants:

   Activity: 12.4 ~ 19.6 Fitness: 6.5 ~ 11.9 Emotional nature: 8.9 ~ 14.1 Regularity: 8 ~ 13 intensity: 11.5 ~ 18.1 Degree of distraction: 8 ~ 12.4 Below or above the normal range are temperament bias.

3. Temperament is innate and there is no difference between good and bad. infants with different temperament need different care.

Single object attention and free play tasks is used to measure the infant's attention capabilities. The tasks assess overall fixation (attention) and looking away (inattention) in regards to novel and familiar objects.

Achieve body weight (grams) of infants and toddlers at each study visit

Achieve body length (cm) of infants and toddlers at each study visit

Achieve head circumference (cm) of infants and toddlers at each study visit

The parent/caregiver need to record the amount of study formula consumed as well as any other infant formula or milk consumed since the last study visit

The parent/caregiver will also be asked to recall the number of bowel movements and the stool consistency seen most often over the 24-hour period. Pictures will be provided to the participant's parent or caregiver for use as a guide in rating the stool consistency.

Questionnaire: What stool consistency was seen most often in your baby's bowel movements over the past 24 hours?(Use pictures provided for reference) (0) No bowel movement;

1. Hard- dry, hard pellets;
2. Formed- definite shape, not dry;
3. Soft-no definite shape, pasty;
4. Unformed or seedy- no shape, some water or small lumps ;
5. Waterly- no shape, mainly water

For option 0~5, 0 and 1 represent poor stool Characteristics , 2-5 represent fine stool Characteristics.

Tolerance information concerning how fussy and gassy the infant has been and if the infant has been more fussy and/or gassy than normal need to be recalled and recorded by parent/caregiver for the 24-hour period prior to the study visit.

Questionnaire:

1. Over the past 24 hours, how fussy has your baby been? (0) Not at all fussy; (1)Slightly fussy; (2) Moderately fussy; (3) Very fussy; (4) Extremely fussy;
2. Over the past 24 hours, ____ was your baby? (0) Less fussy than normal ; (1) About the same level of fussiness as always; (2) More fussy than normal
3. Over the past 24 hours, how much gas has your baby had? (0) Not at all ; (1) Slightly amount of gas; (2) Moderate amount of gas; (3) Excessive amount of gas
4. Over the past 24 hours, did your baby have : (0) Less gas than normal; (1) About the same amount of gas as normal ; (2) More gas than normal

For Question 1 ~ 4, the lower the score, the better.

Number and percentages of infants in each group experiencing any medically-confirmed adverse events and any serious adverse events.

1. A medically-confirmed adverse event is defined as any unfavorable and unintended sign (including an abnormal laboratory finding that is considered clinically relevant by the Health Care Provider), including eyes, ear, nose and throat and the whole body manifestations, respiratory manifestations, dermatologic manifestations, Musculoskeletal manifestations, Metabolism and nutrition manifestations,etc.

2. An adverse event is considered serious if it meets one or more of the following criteria:

   • results in death
   • is life-threatening
   • requires inpatient hospitalization or prolongation of existing hospitalization
   • results in persistent or significant disability/incapacity, or
   • is a congenital anomaly/birth defect

Fecal microbiome analysis of samples collected at enrollment and at 120 days of age

Percentage(%) of infants in each group using any oral antibiotic treatments.

Percentage(%) of infants in each group using intramuscular antibiotic treatments.

Percentage(%) of infants in each group using intravenous (IV) antibiotic treatments.