Effect of Pooling Practices and Time Postpartum of Milk Donations on the Energy, Macronutrient, and Zinc Concentrations of Resultant Donor Human Milk Pools

EGF and IgA in maternal milk, donor milk, and milk fortifiers in the neonatal intensive care unit setting

Human milk contains a variety of factors that positively contribute to neonatal health, including epidermal growth factor (EGF) and immunoglobulin A (IgA). When maternal milk cannot be the primary diet, maternal milk alternatives like donor human milk or formula can be provided. Donor human milk is increasingly provided to infants born preterm or low birth weight with the aim to supply immunological factors at similar concentrations to maternal milk. We sought to assess the concentrations of human EGF and IgA in the diet and stool of neonates between exclusive maternal milk, donor human milk, or formula-based diets. Using a prospective cohort study, we collected samples of diet and stool weekly from premature and low birth weight neonates starting at 10 days postnatal through five weeks of life while admitted to a neonatal intensive care unit (NICU). Compared to formula, there was significantly more EGF in both the milk and the stool of the infants fed human milk. Donor milk pooled from multiple donors contained similar concentrations of EGF and IgA to maternal milk, which was also significantly more than formula diets. Maternal milk supplemented with a fortifier derived from human milk contained significantly more EGF and IgA compared to unfortified maternal milk or maternal milk supplemented with fortifier derived from bovine milk. Further analysis of human milk-derived fortifiers confirmed these fortifiers contained significant concentrations of EGF and IgA, contributing to an increased concentration of those factors that bovine milk-derived fortifiers do not confer. These findings illustrate how the choice of diet for a newborn, and even how that diet is modified through fortifiers or pasteurization before ingestion, impacts the beneficial biomolecules the infant receives from feeding.

Initiation of Enteral Feeding with Mother's Own Milk or Donor Human Milk in Very Preterm Infants: Impact on Bronchopulmonary Dysplasia and Other Prematurity-Related Morbidities

Background: Bronchopulmonary dysplasia (BPD) is a major complication among preterm infants, and nutrition plays a crucial role in its prevention and management. While the nutritional superiority of human milk over preterm formula is well documented, comparisons of the protective benefits of mother's own milk (MOM) versus donor human milk (DHM) in preterm infants are lacking. We aim to investigate if and how the use of MOM or DHM at the initiation of enteral feeding influences the development of BPD and other respiratory outcomes. Methods: This study evaluated the incidence of BPD and other prematurity outcomes in a cohort of 159 very preterm infants (≤32 weeks GA) who commenced enteral feeding with either MOM or DHM. Results: Enteral feeding was initiated with MOM in 75.5% of the infants and DHM in 24.5%. The incidence of BPD was 24.8% (39 infants), and 10.4% (16 infants) developed moderate-to-severe BPD. Univariate and multivariate analyses revealed no significant differences between the MOM and DHM groups in the rates of BPD, other respiratory outcomes, or key prematurity-related morbidities. Conclusions: Despite the unique bioactive properties of MOM, these findings suggest that DHM is a valid alternative that does not significantly increase the incidence of BPD or other clinical outcomes. Further studies are required to determine the relative contributions of milk volumes and feeding practices to the observed findings.

Donor Milk Expression Habits: Can we Favor Hindmilk Banking for Extremely Preterm Infants?

Background: Extremely preterm infants often receive donor milk. Hindmilk, which is released more than 3 minutes after letdown, could be advantageous due to its elevated levels of fat and calorie density. Donor milk expression habits may influence milk composition but have not yet been investigated. This study aims to assess the practices of milk donors and the feasibility of hindmilk expression. Methods: Active milk donors in Québec were questioned using an online survey about their milk expression habits and whether hindmilk donation would be acceptable to them. Answers were analyzed using mixed methods. Results: Of 181 donors, 126 fully completed the questionnaire (70%); 57% reported expressing donated milk between breastfeeds; 15% reported simultaneously breastfeeding while expressing donated milk from the other breast; 12% reported breastfeeding their baby on each breast, then expressing donated milk (hindmilk). The majority (66%) would be willing to change their habits most or all the time to provide hindmilk for preterm infants. The main themes invoked by respondents in open-ended answers were altruism and gratitude for being able to help others. However, 15% commented on the complexity of milk expression or that adding further complexity might discourage them from donating. Conclusions: Expression practices are variable, which may lead to variability in donor milk composition. Most donors would agree to change their expression habits in favor of giving hindmilk to help the most fragile infants. More information is needed on how changing recommendations for milk expression might impact the supply and composition of donor milk.

Mother's Own Milk Versus Donor Human Milk: What's the Difference?

Mother's own milk (MOM) is known to decrease complications in preterm infants and when unavailable, it is recommended that preterm very low-birth weight infants be fed donor human milk (DHM). Due to the pasteurization, processing, and lactation stage of donors, DHM does not contain the same nutritional, immunologic, and microbial components as MOM. This review summarizes the differences between MOM and DHM, the potential effects on health outcomes, and the clinical implications of these differences. Finally, implications for research and clinical practice are discussed.

Pooling Strategies to Modify Macronutrient Content of Pasteurized Donor Human Milk

Background: Donor human milk (DHM) is the recommended feeding for preterm infants when mother's own milk is unavailable or insufficient. DHM macronutrient's variability may have significant implications on preterm growth. Different pooling strategies could be used to improve the macronutrient content, facilitating the achievement of nutritional requirements of preterm. Objective: The aim was to compare the impact of random pooling (RP) and target pooling (TP) strategies on the macronutrient content of DHM and to identify which RP practice allows the achievement of a macronutrient composition as similar as possible to that achievable with TP. Methods: The macronutrient content of 1,169 single-donor pools was analyzed, and a TP strategy combining 2,3,4, or 5 single-donor pools was adopted. On the bases of single-donor pools' analyses, a simulation of 10,000 randomly selected pools for each configuration of donor considered and for different milk volume proportions was performed. Results: Regardless of the type of strategy and milk volume, as the number of donor per pool increases, the percentage of pools with a macronutrient content equal or higher than the reference values for human milk increases. Conclusion: When a TP strategy is not feasible, a RP strategy combining at least five donors should be performed to obtain a better macronutrient content of DHM.

Serum zinc and copper levels in infants admitted to the neonatal intensive care unit

OBJECTIVES

Zinc and copper are trace elements, but their reference values during the neonatal and infant periods are not clear. We aimed to determine the trend of serum zinc levels in infants admitted to the neonatal intensive care unit and compare serum zinc and serum copper levels at admission between small-for-gestational-age (SGA) and non-SGA infants.

METHODS

From 406 patients admitted to the neonatal intensive care unit from January 2009 to September 2012, 339 patients were included in this retrospective study. Blood samples were collected on admission, and serum zinc and serum copper levels were measured. Serum zinc was tested every month until discharge.

RESULTS

Serum zinc levels of infants born at <30 wk of gestation decreased by 46% in the first month of life. All infants born at ≤34 wk of age became zinc deficient at 2 mo of age. The relationship between gestational age and serum zinc level at admission had a negative correlation (Spearman's rank correlation cofficient_s) = -0.66; P < 0.001). There was a negative correlation between serum zinc and serum copper at admission (r_s = -0.49; P < 0.001). Serum copper levels of SGA infants at admission were significantly higher than those of non-SGA infants (P < 0.001).

CONCLUSIONS

All of the infants admitted to the neonatal intensive care unit at ≤34 wk of gestation were zinc deficient by 2 mo of age, suggesting the need for enteral zinc administration. Serum copper was higher in SGA infants than in non-SGA infants on admission, but further studies are needed to determine whether excess copper affects development.

Growth after implementing a donor breast milk program in neonates <33 weeks gestational age or birthweight <1500 grams: Retrospective cohort study

BACKGROUND

Donor breast milk (DBM) feeding has been associated with less growth than formula in preterm infants. Zinc content in DBM is insufficient to support growth in preterm infants.

OBJECTIVE

To compare growth from birth to discharge, macro- and micronutrient intake and the frequency of poor growth before (Epoch-1) and after (Epoch-2) implementing a DBM program.

METHODS

Retrospective cohort study of 1069 infants born at < 33 weeks' gestational age or birthweight < 1500 g and fed using our adjustable feeding protocol with accurate serial length measurements. Growth was assessed by changes in Z-scores of weight, length and fronto-occipital circumference from birth to discharge.

RESULTS

Growth did not decrease significantly in Epoch-2. However, energy and protein intake increased by 5% and frequency of zinc and vitamin D supplementation increased by >30%.

CONCLUSIONS

DBM implementation did not significantly decrease growth from birth to discharge using our adjustable feeding protocol.

Predictors of Breast Milk Zinc Levels Among Breastfeeding Women in Palestine: a Cross-Sectional Study

Zinc is one of the most important essential micronutrients that is needed for the normal growth, development, and maintaining the health of human beings. Previous studies showed that zinc deficiency was highly prevalent among pregnant and lactating women. This cross-sectional study was conducted to determine breast milk zinc levels among breastfeeding women in Palestine and to identify the predictors of breast milk zinc levels. Breast milk samples were obtained from breastfeeding women who visited maternity and primary healthcare centers. Zinc levels were determined using inductively coupled plasma mass spectrometry. Breast milk zinc levels were determined in 390 breast milk samples. The mean breast milk zinc level in all samples was 0.15 ± 0.09 mg per 100 mL. Breast milk zinc levels declined with postpartum time from 0.22 ± 0.011 at ≤ 1 month postpartum to 0.09 ± 0.009 mg per 100 mL at > 9 months postpartum (p-value < 0.001). Multiple linear regression showed that high breast milk zinc levels were predicted by younger maternal age, postpartum time, being employed, frequent consumption of multivitamins/minerals, and practicing exclusive breastfeeding. In conclusion, the breast milk zinc levels quantified among breastfeeding women in Palestine were comparable to those previously reported among non-malnourished women elsewhere. The findings of this study are informative to pediatricians, gynecologists, nurses/midwives, breastfeeding advisors/counselors, nutritionists, and policymakers who might be interested in designing and implementing interventions to improve breast milk zinc levels.

Targeted fortification with human milk analysis: An opportunity for innovation

Human milk's variable macronutrient composition is a necessary consideration when caring for very low birthweight infants. Targeted fortification is the practice of fortifying human milk using its known composition from human milk analysis, rather than its assumed macronutrient values. Utilization of human milk analyzers to measure the protein, fat, lactose, and energy composition within human milk samples has allowed the translation of this practice into the clinical setting. This review discusses the rationale of why targeted fortification is an important practice, what barriers exist in its implementation in the clinical setting, and what research gaps remain to be addressed.

Fortified Donor Human Milk Frequently Does Not Meet Sodium Recommendations for the Preterm Infant

We measured the sodium content of donor human milk (DHM) and calculated the estimated intake at a feeding volume of 160 mL/kg/day. The mean sodium content of unfortified DHM was 102.0 mg/L (4.4 mEq). Because <1% of bovine-fortified samples met the recommended sodium content, infants born preterm who are fed predominantly DHM likely require additional sodium.

Do Maternal Factors and Milk Expression Patterns Affect the Composition of Donor Human Milk?

A primary role of Human Milk Banks (HMBs) is to provide human milk (HM) for preterm infants and to support the mothers of these infants as they establish their own milk supply. A better understanding of the variation in the energy and macronutrients contents of donor human milk (DHM) potentiates targeted nutrition for preterm babies. Therefore, the aim of this study was to assess the variability of energy and macronutrients content in DHM and to investigate the impact of maternal factors and feeding practices on the nutritional value of DHM. The study involved 49 donors registered in the HMB in the Holy Family Hospital in Warsaw, Poland. Samples from each donor were pooled within a maximum of two weeks. The composition of DHM, including energy content, protein, fat, and carbohydrate concentrations, was analyzed using the Miris Human Milk Analyzer. The analyses were performed before the pasteurization process. The mean time of milk donation to HMB was 13.2 ± 6.0 weeks. There were no significant differences in energy and macronutrients contents of DHM in the beginning and at the end of milk donation to HMB, however, HM fat concentration was positively correlated with afternoon feedings (r = 0.289, p = 0.044). The method of feeding (breastfeeding vs. feeding only expressed milk) also did not impact the nutritional value of DHM. Future research for the DHM should include a further cross-sectional observational study with the collection of detailed donor information and characteristics of milk expression and feeding practices to further evaluate the pooling processes and the effect on DHM composition.

Predicting Protein and Fat Content in Human Donor Milk Using Machine Learning

BACKGROUND

Donor milk is the standard of care for hospitalized very low birth weight (VLBW) infants when mother's milk is unavailable; however, growth of donor milk-fed infants is frequently suboptimal. Variability in nutrient composition of donated milk complicates the production of a uniform pooled product and, subsequently, the provision of adequate nutrition to promote optimal growth and development of VLBW infants. We reasoned a machine learning approach to construct batches using characteristics of the milk donation might be an effective strategy in reducing the variability in donor milk product composition.

OBJECTIVE

The objective of this study was to identify whether machine learning models can accurately predict donor milk macronutrient content. We focused on predicting fat and protein, given their well-established importance in VLBW infant growth outcomes.

METHODS

Samples of donor milk, consisting of 272 individual donations and 61 pool samples, were collected from the Rogers Hixon Ontario Human Milk Bank and analyzed for macronutrient content. Four different machine learning models were constructed using independent variable groups associated with donations, donors, and donor-pumping practices. A baseline model was established using lactation stage and infant gestational status. Predictions were made for individual donations and resultant pools.

RESULTS

Machine learning models predicted protein of individual donations and pools with a mean absolute error (MAE) of 0.16 g/dL and 0.10 g/dL, respectively. Individual donation and pooled fat predictions had an MAE of 0.91 g/dL and 0.42 g/dL, respectively. At both the individual donation and pool levels, protein predictions were significantly more accurate than baseline, whereas fat predictions were competitive with baseline.

CONCLUSIONS

Machine learning models can provide accurate predictions of macronutrient content in donor milk. The macronutrient content of pooled milk had a lower prediction error, reinforcing the value of pooling practices. Future research should examine how macronutrient content predictions can be used to facilitate milk bank pooling strategies.

Role of zinc in neonatal growth and brain growth: review and scoping review

This manuscript includes (1) a narrative review of Zinc as an essential nutrient for fetal and neonatal growth and brain growth and development and (2) a scoping review of studies assessing the effects of Zinc supplementation on survival, growth, brain growth, and neurodevelopment in neonates. Very preterm infants and small for gestational age infants are at risk for Zinc deficiency. Zinc deficiency can cause several complications including periorificial lesions, delayed wound healing, hair loss, diarrhea, immune deficiency, growth failure with stunting, and brain atrophy and dysfunction. Zinc is considered essential for oligodendrogenesis, neurogenesis, neuronal differentiation, white matter growth, and multiple biological and physiological roles in neurobiology. Data support the possibility that the critical period of Zinc delivery for brain growth in the mouse starts at 18 days of a 20-21-day pregnancy and extends during lactation and in human may start at 26 weeks of gestation and extend until at least 44 weeks of postmenstrual age. Studies are needed to better elucidate Zinc requirement in extremely low gestational age neonates to minimize morbidity, optimize growth, and brain growth, prevent periventricular leukomalacia and optimize neurodevelopment. IMPACT: Zinc is essential for growth and brain growth and development. In the USA, very preterm small for gestational age infants are at risk for Zinc deficiency. Data support the possibility that the critical period of Zinc delivery for brain growth in the mouse starts at 18 days of a 20-21-day pregnancy and extends during lactation and in human may start at 26 weeks' gestation and extend until at least 44 weeks of postmenstrual age. Several randomized trials of Zinc supplementation in neonates have shown improvement in growth when using high enough dose, for long duration in patients likely to or proven to have a Zinc deficiency. Studies are needed to better elucidate Zinc requirement in extremely low gestational age neonates to minimize morbidity, optimize growth and brain growth, prevent periventricular leukomalacia and optimize neurodevelopment.

Animal Models for In Vivo Lactation Studies: Anatomy, Physiology and Milk Compositions in the Most Used Non-Clinical Species: A Contribution from the ConcePTION Project

Simple Summary

Nowadays, the importance of breastfeeding has been very well recognized not only by the scientific world but also by public opinion. Such awareness has nonetheless put a lot of pressure on women under chronic pharmacological medication, or that simply need to alleviate common post-partum health issues, due to the lack of scientific data regarding the potential transfer to the offspring during lactation. In such a scenario, the ConcePTION project aims at creating a trusted ecosystem that can efficiently generate and disseminate reliable evidence-based information regarding the effects of medications used during pregnancy and breastfeeding to women and their healthcare providers. Due to the need for a reliable animal species to obtain scientific data, the present review summarizes the main features contributing to the lactation process in the most commonly used laboratory animal species.

Abstract

The present review aims to summarize the main features of mammary gland anatomy, and the physiology of lactation and colostrum/milk in the most commonly used animal species for regulatory toxicity. The final goal is the selection of a preferred animal species to be enrolled in studies investigating the potential transfer of drugs and exogenous molecules through milk, within the Innovative Medicines Initiative (IMI) funded project ConcePTION. Reference data regarding humans were also collected and analyzed in order to highlight critical similarities and differences with the studied species. Additional practical considerations were also taken into account, such as ethical consideration regarding the chosen species which affects the group size, financial implications and technical feasibility of lactation trials (e.g., ease of sampling, volume of sampling, husbandry requirements and scientific recognition). In conclusion, the present analysis of the literature confirms the complexity of the decisional process behind the choice of an animal model for in vivo trials. For some of the evaluated species, data were either poor or missing, highlighting the necessity to generate more physiological background studies for species that are routinely used in laboratory settings. Overall, when taking into consideration ethical factors, feasible group size, milk volume and ease of milk collection, and physiological similarities with humans, minipigs seem to represent the most appropriate choice.

Effects of milk banking procedures on nutritional and bioactive components of donor human milk

Pasteurized donor human milk is in wide use for preterm infants in neonatal intensive care units when maternal milk is unavailable. Pasteurization of donor milk is required to prevent bacterial contamination, and multiple methods are used in the non-profit and commercial milk banking industries. Pasteurization results in changes in the nutrient and bioactive components in donor milk compared to unpasteurized human milk, and these changes vary by the type of pasteurization process. Other milk bank practices including freezing of milk, pooling of milk from multiple donors and use of pre-processing macronutrient analysis also affect the nutritional composition of donor milk. This review compiles evidence regarding three common pasteurization techniques for donor milk: Holder pasteurization, vat pasteurization, and retort pasteurization and their effects on the nutritional content and bioactive factors in human milk. It also includes review of literature investigating the impact of freezing and storage, and best practices for multi-donor milk pooling.

Concentrating human milk: an innovative point-of-care device designed to increase human milk feeding options for preterm infants

OBJECTIVE

The purpose of this study was to determine whether a point-of-care osmotic device concentrates important human milk (HM) nutrients to support feeding neonates requiring high-nutrient, low-volume feedings.

STUDY DESIGN

Raw and pasteurized HM samples were concentrated to determine the effects of time and temperature on concentration. Concentrated samples were compared with matched baseline samples to measure changes in selected nutrient concentrations. Furthermore, changes in concentration of certain bioactive components of raw milk samples were measured.

RESULT

The device significantly increased the concentrations of the majority of the measured nutrient and bioactive levels (p < 0.05). Increasing temperature of HM from 4 to 37 °C increased the concentration rate >30%. In all cases, the concentration rate of pasteurized HM was greater than that of raw HM.

CONCLUSIONS

The osmotic concentration of HM is a promising option for neonatal nutrition. Further studies are needed to establish an evidence base for the practical applications of this point-of-care device.

Methods of mixing donor human milk during bottling results in fat differences between samples within a pool

The influence of milk-banking processes on nutrients in donor human milk (DHM) is largely unknown. Previous studies have measured nutrients between pools of DHM, but within-pool nutrient differences (between bottles from the same pool) have yet to be elucidated. The objective of this study was to gain a better understanding of the effect of different mixing characteristics on the distribution of fat, protein, IgA, and lysozyme in bottled, raw DHM. Pools of DHM were created in a laboratory setting according to published human milk-banking guidelines and assigned to a mixing treatment (mixing during bottling method, pooling container material, and refrigerated hold time). Four mixing protocols using glass pooling containers and a 1-h refrigerated hold time were tested: control (no mixing during bottling); manual-A (Man-A, hand swirl after pouring 3 bottles); manual-B (Man-B, hand swirl after pouring every bottle); and mechanical-G (Mech-G, continuous stirring with a magnet). As secondary objectives, we compared the effect of a glass and a plastic pooling container with mechanical mixing (mechanical-P, Mech-P), and compared refrigerated delays of 1 and 24 h before bottling with manual mixing (manual-A24, Man-A24). To control for differences in nutrient content, comparisons between treatments were made using absolute percent difference from the treatment-specific mean; and comparisons within a treatment were made using the ratio of fat content in a bottle to fat content in the first bottle of the same pool. We did not observe differences in nutrient distribution between Man-A, Man-B, and Mech-G in pools held for 1 h, but all were significantly different from the control for fat. There were no differences between glass or plastic pooling containers when mechanical mixing was used. Holding a pool in the refrigerator for 24 h before bottling created significantly greater fat distribution than holding a pool for 1 h. Outcomes were the result of controlled experiments. In summary, manual and mechanical mixing of 1,700-mL DHM pools produces similar fat and protein distributions when DHM is pooled and bottled after a 1-h hold time. When DHM is held for 24 h before bottling, more research is needed to determine the duration of initial mixing needed to reduce fat variability between bottles.

Zinc deficiency limiting head growth to discharge in extremely low gestational age infants with insufficient linear growth: a cohort study

OBJECTIVE

To assess the relationship of size for age with zinc deficiency in extremely low gestational age (GA) infants (23-28 weeks, ELGANs) who had insufficient linear growth despite optimizing other nutrients and to analyze changes in fronto-occipital circumference (FOC), weight and length with zinc supplementation.

STUDY DESIGN

Retrospective cohort study.

RESULTS

Among 302 ELGANs, a serum zinc concentration was obtained in 52 with insufficient linear growth (17%). Zinc deficiency (serum concentration <0.74 mcg/ml) was diagnosed in 8 of 24 (33%) small for GA (SGA) compared to 35 of 278 (13%) non-SGA infants (P = 0.01). Zinc supplementation for >2 weeks improved FOC growth to discharge or 50 weeks postmenstrual age in infants with Zn deficiency. However, neither linear growth nor weight gain improved with Zn supplementation.

CONCLUSION

Zinc deficiency was diagnosed in 14% ELGANs in this cohort. Zinc supplementation for >2 weeks improved FOC growth but not linear growth or weight gain.

Milk Bank Pooling Practices Impact Concentrations and Variability of Bioactive Components of Donor Human Milk

Background: Donor human milk (DHM) bank practices, such as pasteurization and pooling according to postpartum age of milk donations and number of donors included in a pool may impact the resulting concentration of bioactive components of DHM. Aims: We determined the impact of Holder pasteurization, postpartum milk age, and pool donor number (number of donors included in a pool) on resulting concentrations of total immunoglobulin A (IgA; which provides immune protection to the recipient infant) and insulin (an important hormone for gut maturation).We also documented inter-relationships between these bioactive components and macronutrients in DHM pools. Methods: Pre and post-pasteurization aliquots of 128 DHM samples were obtained from the Rocky Mountain Children's Foundation Mother's Milk Bank (a member of the Human Milk Banking Association of North America, HMBANA). Macronutrients were measured via mid-infrared spectroscopy. Total IgA was measured via customized immunoassay in skim milk and insulin was measured via chemiluminescent immunoassay. Results: Mean post-pasteurization total IgA concentration was 0.23 ± 0.10 (range: 0.04-0.65) mg/mL a 17.9% decrease due to pasteurization (n = 126). Mean post-pasteurization DHM insulin concentration was 7.0 ± 4.6 (range: 3-40) μU/mL, a decrease of 13.6% due to pasteurization (n = 128). The average DHM pool postpartum milk age was not associated with total IgA or insulin concentrations, but pool donor number was associated with bioactive components. Pools with only one donor had lower total IgA and lower insulin concentrations than pools with at least 2 donors (p < 0.05). Increasing the number of donors in a pool decreased the variability in total IgA and insulin concentrations (p < 0.04). Conclusion: Increasing the number of donors included in DHM pools may help optimize bioactive components in DHM received by premature infants. These results help inform milk banking practices to decrease compositional variability in produced DHM pools.

Fat and Protein Variability in Donor Human Milk and Associations with Milk Banking Processes

Background: The impact of milk banking processes on macronutrient variability in donor human milk (DHM) is largely unknown. Objective: To gain a better understanding of fat and protein composition in DHM and assess potential relationships with modifiable milk bank processes. Methods: Samples of raw, pooled DHM were collected from 20 milk banks (n = 300) along with the following processing attributes: if macronutrient analysis was used to select donors for pooling (target pooling; yes/no), number of donors per pool, pooling container material (glass/plastic/other), and method for mixing during bottling (manual/mechanical). Fat and protein were assessed. Homoscedasticity was assessed and magnitude of the spread was quantified. Results: Fat ranged from 1.9 to 6.1 g/dL (n = 298) and protein ranged from 0.7 to 1.4 g/dL (n = 300). Variability in fat was significantly lower in samples that had been target pooled (p = 0.04), contained more donors per pool (p < 0.001), and had been mixed mechanically (p < 0.001). Variability in protein was significantly lower in samples that contained more donors per pool (p = 0.001). In a stratified analysis, increasing the number of donors per pool only reduced nutrient variability in samples that were not target pooled. Conclusion: For milk banks that do not target pool, using a greater number of donors in a pool may reduce fat and protein variability.