Suckling Patterns Research Articles

SmartLact8: A Bio-Inspired Robotic Breast Pump for Customized and Comfort Milk Expression.

According to the 2018 National Immunization Survey conducted by the Center for Disease Control and Prevention (CDC), 83.9% of the breastfeeding mothers in the United States have used a breast pump at least once. However, the majority of existing products use a vacuum-only mechanism to extract milk. This causes common breast injuries such as nipple soreness, breast-tissue damage, and lactation complications after pumping. The objective of this work was to develop a bio-inspired breast pump prototype, named as SmartLac8, that can mimic infant suckling patterns. The input vacuum pressure pattern and compression forces are inspired from term infants' natural oral suckling dynamics captured in prior clinical experiments. Open-loop input-output data are used to perform system identification for two different pumping stages that facilitates controller design for closed-loop stability and control. A physical breast pump prototype with soft pneumatic actuators and custom piezoelectric sensors was successfully developed, calibrated, and tested in dry lab experiments. Compression and vacuum pressure dynamics were successfully coordinated to mimic the infant's feeding mechanism. Experimental data on sucking frequency and pressure on the breast phantom were consistent with clinical findings.

Suckling Behaviour of Beef Calves during the First Five Days Postpartum

Observations of 17 heifer-calf pairs were collected over the first 5 days postpartum (p.p.) to study nursing and maternal behaviour of beef cattle. Cattle were managed in a 6 ha paddock and heifer–calf interactions were determined from both regular visual observations and video recordings. Of 17 potential calves, one was stillborn and 3 died in the first 5 days p.p. associated with dystocia and congenital malformation. Four further potential neonatal calf mortality risks were identified, which included poor calving site selection (n = 1), calf misadventure (n = 1), heifer-calf separation (n = 3) and mismothering (n = 3), with each resulting in distress, physical exhaustion of the calf and impaired nursing. There was marked variation between heifers in the expression of optimal maternal behaviours, with only 39% classified as ‘good’ mothers. Dam terminated nursing bouts were 27% shorter in duration than calf terminated nursing bouts; 29% of heifers terminated nursing bouts at least 50% of the time. Only 68% of observed suckling interactions were considered effective. On average, the nursing behaviour lasted 7.0 min, with sucking making up 54% of the total nursing time, the sucking rate was 2.0 sucks/s, and the calves performed 7.5 teat-switches, 2.4 butts and 0.9 teat-strips per min of nursing. In 67% of nursing interactions, the calves sucked on all four teats. By three days p.p., all calves developed a clear, consistent suckling pattern. Prior to this, the calves had shorter nursing bouts, spent less time nursing and manipulating the udder, paused more, switched teats and butted less, and had a slower sucking rate. The behaviour of some calves (i.e., low teat fidelity and high levels of milk stimulation behaviours) suggested that their dam milk availability was low. This study has quantified early post-partum nursing behaviour of neonatal beef calves and highlighted dam and calf behaviours that may adversely affect milk intake and, therefore, impact calf survival.

In Vitro Flow Visualization in a Lactating Human Breast Model.

Human milk extraction from the breast is affected by the infant's oral activities. Natural suckling by the infant includes both intraoral vacuum and peripheral oral compression during breastfeeding. However, the contribution of each of these motions to milk extraction at the outlet and at the duct bifurcations is unclear. In this work, we investigated the flow field in a lactating breast model considering bifurcated milk ducts and multiphase breast-infant interactions. A bio-inspired breastfeeding simulator device was utilized to mimic an infant's oral feeding mechanism during breastfeeding and extract the human milk-mimicking Fluid from the transparent and elastic lactating breast phantom during experiments. Using a particle image velocimetry system, we found that the oscillatory flow under vacuum pressure provides a higher velocity field at the outlet compared to that when an infant applies both vacuum and oral compression pressures. Additionally, the intraoral vacuum coordinated with the oral peripheral compression causes stronger vorticities and secondary flows at the adjunction of the bifurcated ducts than the vacuum-only case. Vacuum-only extraction yields an increase in flow velocity at the outlet and could be one of the reasons for nipple pain, whereas infant's oral activities on the breast generated more vortices in the milk duct adjunctions and might cause milk duct clogs. This phenomenon is rationalized based on the validation of a previous in vivo clinical study of milk production compared between commercial pumps and infant suckling. The fact that milk consumption of vacuum-only extraction is less than that of vacuum plus oral compression further explains the effectiveness of applying a natural suckling pattern in human lactation.

Early skin contact combined with mother\u2019s breastfeeding to shorten the process of premature infants \u2264 30 weeks of gestation to achieve full oral feeding: the study protocol of a randomized controlled trial

BackgroundMost hospitalized preterm infants experience difficulties in transitioning from tube feeding to full oral feeding. Interventions to promote full oral feeding in preterm infants in the neonatal intensive care unit (NICU) are limited to pacifier use or bottle-feeding exercises. Skin contact has been shown to be beneficial to start and maintain lactation and provide preterm infants with the opportunity to suck on the mother’s breast, which may promote further development of the preterm infant’s suckling patterns. The objective of this study is to compare and evaluate the effects of skin contact combined with breastfeeding (suck on the mother’s empty breast) as compared to the routine pacifier suckling training model in achieving full oral feeding for infants whose gestational age are ≤ 30 weeks.MethodsThis is a single-center, randomized controlled clinical trial conducted in the NICU and designed according to the SPIRIT Statement. The subjects included in the study are premature infants born between April 2020 and July 2021 with a gestational age of ≤30 weeks, birth weight of <1500 g, admission age of <72 h, and absence of congenital malformations. Those with oxygenation indices of >40 and those born to mothers with poor verbal communication skills will be excluded. A sample of 148 infants is needed. The infants will be randomized to the intervention (skin contact combined with mother’s breastfeeding model) or control group (routine pacifier sucking training model). The primary outcome is the time required to achieve full oral feeding. The secondary outcomes are the breastfeeding abilities of preterm infants as assessed by the Preterm Infant Breastfeeding Behavior Scale (PIBBS), breastfeeding rates at 3 and 6 months corrected gestational age, complication rates, duration of oxygen requirement, days of hospital stay, and satisfaction of parents.DiscussionThis paper describes the first single-center, open-label, randomized clinical trial on this topic and will provide crucial information to support the implementation of skin contact combined with the breastfeeding model in the NICU setting.Trial registrationClinicalTrials.gov NCT 04283682. Registered on 8 February 2020.

The effect of milk quantity and feeding frequency on calf growth and behaviour

Context Calves left with their dam to suckle will consume ~7–12 L/day; however, the amount of milk provided to dairy young calves removed from their dams may often be as low as 4 L/day, or 10% of their bodyweight. Aims This study compared once and twice daily feeding, as well as feeding levels of 10 and 20% of bodyweight and studied the effect on behaviour and metabolic indicators indicative of hunger. Methods Forty-six male dairy calves were allocated to one of three treatments from 3 to 8 days of age: (i) 10% of bodyweight offered daily as one meal (1 × 10%, n = 16); (ii) 10% of bodyweight offered daily over two meals (2 × 5%, n = 15); or (iii) 20% of bodyweight offered over two meals (2 × 10%, n = 15). Behaviour during and after feeding was observed by video, and blood samples taken on selected days were analysed for glucose, nonesterified fatty acids (NEFA), cortisol and packed-cell volume. Key results Milk intake on Days 3 and 4 was lower in those calves fed once daily compared with calves fed twice daily. Calves fed at 20% bodyweight had higher milk intake compared with calves fed at 10% bodyweight on all days other than Day 3 and growth was higher in those calves. Non-nutritive sucking was mainly associated with feeding times and it was highest in calves fed 10% bodyweight over two meals, with a suckling pattern that suggested that feeding at 10% bodyweight satisfied feeding motivation less than feeding at 20% bodyweight. Play behaviour was reduced in calves fed once daily, suggesting hunger and reduced welfare. There were significant effects on physiological indicators of metabolic state. NEFA concentrations were significantly higher in calves fed once daily and calves fed 10% of bodyweight at certain time points, indicating a lower energy balance. Conclusions Feeding twice daily offers benefits to calves up to Day 4 of life whereas feeding 20% of bodyweight was beneficial after Day 4 to increase satisfaction of feeding motivation and nutrition for growth. Although metabolic variables were within normal physiological range for all treatments, the effects on feed intake, growth and non-nutrient sucking suggest marked effects on hunger when calves are fed the lower milk allowance. Implications The fairly common practice of feeding dairy calves 10% of bodyweight, in one or two daily meals may leave calves hungry, and an increase in milk allowance should be considered.

Comment on David Haig's 'Troubled sleep': Implications for functions of infant sleep

Comment on David Haig's 'Troubled sleep': Implications for functions of infant sleep

Formation of teat order and estimation of piglets’ distribution along the mammary complex using mid-domain effect (MDE) model

Domestic piglets (Sus scrofa domesticus) establish relatively stable teat order after the first week postpartum. Formation of teat order is normally accompanied by intense competition between littermates. In this period, piglets’ behaviour and their distribution along the mammary complex is subject to various external influences. In the present study, time-dependent changes of suckling pattern in domestic piglets and the potential factors affecting piglets’ suckling distribution along the mammary complex were investigated. Eleven sows with their litters (110 piglets) were included in the analysis. Throughout the lactation period there were 27 observations per litter. In addition to milk intake and piglet body weight we focused on the impact of geometric constraints (physical limitation of the mammary complex), which has previously been disregarded in studies of piglet suckling behaviour but could play a crucial role, especially at the beginning of the lactation period. Changes in piglets’ distribution were analysed for correlation with changes in milk intake and body weight during lactation. The impact of geometric constraints was estimated using mid-domain effect (MDE) models. Analysis of the first two-weeks of lactation revealed that teat order stability increased after the first week, reaching a transition maximum by the second week (58%), when the effect of geometric constraints was still significant (r2=0.679; p<0.05). Longer periods of lactation led to consistent suckling order, which was no longer affected by geometric constraints (p≥0.05). Alteration of piglet distribution was not associated with the quantity of milk they consumed (r2=0.612; p>0.05). Variation in milk intake was explained by piglet body weight (r2=0.701; p<0.05). Results indicate that the physical limitation of the mammary complex was the only factor that directly affected piglets’ distribution, which was thereby subject to the MDE. The MDE model enabled precise estimation of the piglets’ behaviour on the mammary complex and provides novel information towards understanding of the suckling process.

The Pattern of Nipple Use Before Weaning Among Littermates of the Domestic Dog

AbstractSuckling provides a well‐defined and functionally significant context in which to study mammalian sibling competition and the possible consequences of this for long‐term differences in individual behavior, physiology, and life histories. There have, however, been surprisingly few studies of suckling behavior, even in species as accessible as the domestic dog. In a first approach, we filmed the suckling behavior of 10 litters (47 puppies) of various dog breeds in their owners' homes during the first postnatal month before the start of weaning. The pattern of nipple use was very similar across litters but very different to that of the better‐studied pig or cat. Puppies showed only weak preference for particular (central) nipple rows, they often switched nipples during nursing sessions and showed no evidence of teat consistency in which each littermate uses primarily one or two particular nipples. They also showed very little agonistic behavior that could be interpreted as contesting access to nipples. The present findings provide a reminder of the diversity of suckling patterns among altricial mammals and of the need for more comparative information to better understand the reasons for and functional significance of such differences.

Feeding skill milestones of preterm infants born with extremely low birth weight (ELBW)

AimTo compare the feeding development of preterm infants with that of full-term infants. ParticipantsNineteen preterm infants with extremely low birth weight, and 11 healthy full-term infants. MethodsIntensive follow-up study. Feeding situations were analyzed by NOMAS (Neonatal Oral Motor Assessment Scale) and by an oral motor patterns checklist based on video recorded sessions. ResultsMost of the preterm infants showed a disorganized sucking pattern and most of the full-term infants a normal sucking pattern, as long as suckling was present. However, the early suckling pattern did not predict the schedule of later feeding development. Preterm infants seemed to learn the various feeding skills at the same corrected ages as full-term infants, with the exception of munching, which they learned earlier than the full-term infants. However, the age range for gaining these skills was wider for the preterm infants. Preterm infants also seemed to have feeding problems more often than full-term infants when qualitative features of feeding were considered. Feeding was prolonged and messy, and the preterm infants were sensitive to different qualities of food. ConclusionFeeding development of preterm and full-term infants is similar except for suckling, when only oral motor skills are concerned. When the qualitative characteristics of feeding are taken into account, the preterm infants suffer from feeding problems that create a risk for early interaction and communication.

Sex differences in the mother–neonate relationship in wild baboons: social, experiential and hormonal correlates

In mammals, maternal care is essential for offspring survival, yet individual differences in this care can dramatically affect offspring growth and development. Few studies have, however, investigated the sources, magnitude and consequences of naturally occurring interindividual variation in maternal care during the neonatal period. In this study, we examine several hormonal and nonhormonal predictors of naturally occurring variation in the mothereneonate relationship during the first 8 weeks of infancy in 34 wild baboon (Papio cynocephalus) mothereinfant dyads in Amboseli, Kenya. We use data on physical contact and suckling patterns to assess the quality of the mothereneonate relationship and to evaluate the extent to which variation in this relationship is predictable from perinatal ovarian steroids (i.e. faecal oestrogen and progesterone metabolites), previous infant care experience, maternal dominance rank and offspring sex. We found that newborn infants of more experienced mothers initiated higher rates of changes in mothereinfant contact than newborns of less experienced mothers. However, at each level of maternal experience, newborn males initiated higher rates of changes in mothereinfant contact than newborn females. Moreover, we found evidence suggesting that variation in suckling activity among daughters (but not sons) was predictable from maternal dominance rank and faecal oestrogen (fE) concentrations before birth. To our knowledge, our study provides the first evidence of (1) the influence of cumulative maternal experience on the mothereinfant relationship and (2) the emergence of sex differences in the mothereinfant relationship during the neonatal period in wild primates. Our results suggest that the well-documented sex differences in life history, behaviour and ecology in primates (and other social mammals) may originate very early in life. 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. For vertebrates, mammalian newborns are unusually dependent on their mothers for nourishment, transport, protection and support (Clutton-Brock 1991). Although offspring eventually transition from complete reliance on their mothers to nutritional, locomotor and social independence, the timing of these events can vary widely across individuals of the same species (Clutton-Brock 1991). Despite the critical importance of the neonatal period in the life of each individual, few studies have investigated the sources, magnitude and consequences of interindividual variation in the mothereoffspring relationship during the neonatal period in wild mammals (Altmann 1980; Bales et al. 2002). In this study, we

Distribution of Slow Muscle Fiber of Muscle Spindle in Postnatal Rat Masseter Muscle

We investigated the properties of the muscle spindle in the masseter muscle at an immunohistochemical level in rats fed for 6 weeks. Slow myosin heavy chain (MyHC) isoforms were measured and intrafusal fibers in the muscle spindle were studied to determine the relationship between the superficial and deep regions of rat masseter muscle after alternated feeding pattern. However, muscle spindles were found in both regions, mainly in the deep region of the posterior superficial region of masseter muscle. The total number of the slow fiber in the intrafusal fiber and number of muscle spindle in the deep region were high from 5 to 8 weeks old in spite of various dimensions of data such as diameter and the compositions of the intrafusal fiber. The relationship of the protein expression of slow MyHC in the two regions at 5 weeks old reversed five weeks later (10 weeks old). This period is an important stage because the mastication system in masseter muscle with muscle spindle may be changed during the alternated feeding pattern of suckling to mastication. The changes may be a marker of the feeding system and of the control by the tension receptor of muscle spindle in this stage of masseter muscle after postnatal development.

Milk intake and development in a newborn captive African elephant (Loxodonta africana)

In August 2003 the San Diego Zoo's Wild Animal Park (WAP) and the Lowry Park Zoo, under the auspices of the AZA's Elephant SSP and a USFWS permit, imported 3.8 African elephants (Loxodonta africana) from the Kingdom of Swaziland. When they were captured, transrectal ultrasound examinations revealed that one nulliparous cow was approximately 10 months pregnant. At the time of their arrival (August 2003), all of the animals were estimated to be approximately 13 years old and were thought to be nulliparous. Based on the ultrasound examination results and the average African elephant gestation period, parturition was predicted to be 20 February 2004. In this report, we provide the first detailed data about nursing activity around the clock and newborn calf development, describe maternal and neonatal nighttime activity budgets, and explore maternal weight changes during suckling and lactation. The newborn calf suckled significantly more at night than during the day, but suckled for only about 2 hr per 24-hr period. Regression analysis revealed that through the first 3 months of life the calf gained 0.385 kg/day while it suckled on a regular basis. We compare our findings with published information on wild elephants, and conclude that although the growth rate is reduced compared to hand-reared elephant calves, the suckling patterns are almost identical to those reported for wild calves. Zoo Biol 0:1–7, 2005. © 2005 Wiley-Liss, Inc.

Influence of milking and restricted suckling regimes on milk production and calf growth in temperate and tropical environments

AbstractTwo experiments were carried out to investigate the effect of restricted suckling and milking regimes on milk yield, milk composition and calf growth. Experiment 1 was carried out in temperate conditions in the United Kingdom and experiment 2 under tropical conditions in Mexico. In experiment 1 a Latin rectangle (change-over) design with 3-week periods was used with eight Holstein Friesian cows suckling their Simmental-sired calves. Saleable milk yield (SMY), sucked milk (CSM), milk composition and calf performance were studied. The treatments were: once a day milking (a.m.) with suckling immediately after (1χAM); once a day milking (a.m.) with suckling p.m. (1χPM); twice daily milking with suckling after a.m. milking (2χAM); twice daily milking with suckling after each milking (2χ2χ). The cows were offered maize silage ad libitum and 4·3 kg dry matter (DM) per day of rapeseed meal plus minerals and vitamins. The calves had ad libitum access to concentrates (165 g crude protein (CP) per kg DM) and wheat straw. In experiment 2, 11 B. indicus χ B. taurus cows, suckling their Brahman-sired calves were used in an experiment with the same treatments and experimental design. Cows were offered star grass (Cynodon nlemfuensis) hay ad libitum and 4.0 kg DM per day of concentrate (117 g CP per kg DM). The calves had ad libitum access to concentrate (151 g CP/kg DM), star grass hay and Ramon leaves. For 1χAM, 1χPM, 2χAM and 2χ2χ respectively in experiment 1, the total milk yields (TMY = SMY + CSM) were 17.9, 18.0, 16.7 and 19.5 kg/day (s.e.d. 1.11) and SMY represented 0.70, 0.45, 0.77 and 0.53 of TMY. Corresponding results for experiment 2 were 6.0, 6.2, 7.0 and 7.1 kg/day (s.e.d. 0.32) and 0.69, 0.45, 0.78 and 0.61. Effects of treatment on milk yield and composition were consistent with the feedback inhibitor of lactation theory. It was concluded that different milking and restricted suckling patterns can be used to manipulate saleable milk production and calf growth. Holstein Friesian dairy cattle in a restricted suckling system without the calf presence at milking, behaved similarly to zebu-crossbred cows by reducing milk let down at milking.

Continuously recorded suckling behaviour and its effect on lactational amenorrhoea.

The hypothesis that the month-specific rate of return to ovarian cyclicity after childbirth is causally related to suckling pattern was tested for a population of New Mexican women recruited within the service area of New Mexico Highlands University and for a nationwide USA subpopulation of women recruited through membership of the Couple to Couple League (CCL). Survival analysis for time-dependent covariates was used, and significant predictors of the first postpartum menses were found. Important differences were detected in the suckling pattern for the two groups and a 5:2 differential was found in their respective rates of menstrual cycle recovery. Although the two groups were comparable perinatally, daily and time-windowed breast-feeding performance fell off at twice the rate for the New Mexico population when contrasted with the CCL sample. For both populations, the introduction of solid feeds was a strong and significant predictor of returning menstrual cyclicity, independent of suckling pattern.

Neurobiology of mother–infant interactions: experience and central nervous system plasticity across development and generations

The optimal coordination between the new mammalian mother and her young involves a sequence of behaviors on the part of each that ensures that the young will be adequately cared for and show healthy physical, emotional, and social development. This coordination is accomplished by each member of the relationship having the appropriate sensitivities and responses to cues that characterize the other. Among many mammalian species, new mothers are attracted to their infants’ odors and some recognize them based on their odors; they also respond to their infants’ vocalizations, thermal properties, and touch qualities. Together these cues ensure that the mother will nurse and protect the offspring and provide them with the appropriate physical and stimulus environment in which to develop. The young, in turn, orient to the mother and show a suckling pattern that reflects a sensitivity to the mothers odor, touch, and temperature characteristics. This article explores the sensory, endocrine, and neural mechanisms that underlie this early mother–young relationship, from the perspective of, first, the mother and, then, the young, noting the parallels between them. It emphasizes the importance of learning and plasticity in the formation and maintenance of the mother–young relationship and mediation of these experience effects by the brain and its neurochemistry. Finally, it discusses ways in which the infants’ early experiences with their mothers (or the absence of these experiences) may come to influence how they respond to their own infants when they grow up, providing a psychobiological mechanism for the inter-generational transmission of parenting styles and responsiveness.

Primigravidity, body weight, and costs of rearing first offspring in rhesus macaques.

Body size is associated with menarche and ovarian function, but the relationship to first conception is rarely examined. We conducted a longitudinal investigation of rhesus macaques, Macaca mulatta, to determine the effect of differences in body weight on both the age at first conception and survivorship of first progeny. Young females who became pregnant weighed significantly more than peers who remained barren, with weight changes for females who successfully raised offspring no different than those for females who did not produce offspring. Infant mortality among primiparae was not significantly greater than that among multiparae, although nearly twice as high. First-born males tended to have lower survivorship than first-born female offspring. We suggest that reproductive costs encountered by primiparous females are more likely to be modulated by immature neuroendocrine function than by inexperience, small body size, or infant suckling patterns. We conclude that body size influences probability of first conception, socioendocrine factors mediate the likelihood of infant survival, and primiparous production of male progeny seems to exert a greater reproductive cost than does production of female progeny.

Effect of familiarity with the environment on the behaviour and performance response of sows and piglets to grouping during lactation

To determine whether the disruption in suckling patterns and cross-suckling which are observed in multisuckling systems could be reduced by modifying pen design to permit prior familiarity of animals with the environment, 32 Large White×Landrace sows and litters were allocated between two treatments, each with four replicate groups of four sows and litters. On Day 7 after farrowing, T1 sows and litters were moved from individual farrowing crates to a modified multisuckling pen, where each sow and her piglets were enclosed in an individual pen, whilst T2 sows and litters remained in the farrowing house. Grouping occurred on Day 14; in T1 the gate behind each individual pen was opened to allow the animals voluntary access to a communal area. T2 animals were moved directly from the farrowing house and grouped in an unfamiliar multisuckling pen of the same size with conventional open layout and a single large creep area for the piglets. Overall mortality rate in the two systems was not significantly different, but more piglets tended to be crushed in each treatment in the week following first transfer to the experimental pens ( P<0.10). Frequency of suckling attempts (1.47 vs. 0.95 per hour, S.E.D. 0.05, P<0.01) and proportion of suckling attempts which resulted in milk letdown (0.60 vs. 0.40, S.E.D. 0.07, P=0.06) were lower for T2 than T1 on the day of grouping. The proportion of piglets cross-suckling per litter after grouping was greater in T2 (0.58 vs. 0.22, S.E.D. 3.14, P<0.01). Piglets in T1 spent a greater proportion of time close to their own mother (e.g. 0.45 vs. 0.12, S.E.D. 0.082, P<0.05 on Day 14). Piglet growth rate was significantly reduced in T1 between Day 7 and 14 (211 vs. 260 g/day, S.E.D. 15.3, P<0.01) but only slightly better than T2 after grouping (221 vs. 213 g/day, S.E.D. 7.2, for Days 14–28). After weaning, performance did not differ significantly between piglets from the two systems. Familiarity with the new environment before grouping, and/or greater structural complexity within the pen, therefore reduced the disruption in suckling behaviour after grouping and reduced the incidence of cross-suckling, but did not yield performance benefits.

Exogenous Oxytocin Attenuates Suckling-Induced Prolactin Release but Not Maternal or Infant Behavior in Lactating Rats

The influence of exogenous oxytocin (OT) on maternal and infant behavior over 60 min of suckling, which followed 6 h of isolation, was investigated on Day 12 of lactation in rats. Mothers administered 1 IU of OT or saline through an indwelling atrial catheter and their litters indicated a similar nursing and suckling pattern, which was estimated by the crouching time of the mothers and the number of stretch reactions performed by the litters during a suckling period. To assess the alteration of the suckling intensity by OT administration, the plasma prolactin (PRL) level was determined by an Nb 2 lymphoma cell bioassay. In the control group, the plasma PRL level increased and reached a peak at 45 min after the onset of suckling in 60% of the animals. The suckling-induced PRL release was completely inhibited and/or markedly delayed by OT administration. The difference in body weight of the litters before and after a suckling period was estimated as an index of the amount of milk suckled by the litters. There was no difference in the amount of milk between the control and OT-treated groups during a 60-min suckling period. However, it was significantly greater in the OT-treated group during the first 20 min of the suckling period. These results indicate that a dose of OT is a factor in the attenuation of the intensity of suckling done by the pups, whereas the nursing and suckling behavior is not influenced by OT administration.

Effects of Under- and Overnutrition on Lactation in Laboratory Rats ,

To study the effects of maternal nutritional status on lactational performance, the diets of laboratory rats were manipulated with food restriction or increases in fat concentration. Compared with rats fed control diets ad libitum, conception rate, milk production and litter growth decreased and milk fat concentration increased in both chronically food restricted and obese animals. Chronically food restricted rats mobilized body fat and reduced their energy expenditure for maintenance and activity. Differences in suckling pattern between control and food-restricted rats affected hormone concentrations important for successful lactation. Obese rats experienced greater difficulty than controls in delivering their pups and more of their pups died in the first days of life. Milk production among obese rats may be constrained by poor appetite and the high heat production that characterizes lactation in litter-bearing species. There are many parallels as well as important differences between results obtained from these models and findings in nursing women. Nevertheless, these models provide useful information about the possible mechanisms by which maternal nutritional status affects lactational performance. J. Nutr. 128: 390S’393S, 1998.

In-depth study of breastfeeding structure: New data from Mali.

A number of variables, including ethnic affiliation, time of day, infant and maternal ages, and infant dietary supplementation, are used to compare their effects on breastfeeding structure of two groups of rural Malian women. The agro-fishing Bozo and the transhumant pastoralist Fulbe live in the Inner Niger Delta of Mali. On-demand breastfeeding is practiced by these groups. Lactation continues throughout the infant's second year of life and often into the third. Comparisons are made with data from other traditional societies to highlight differences in breastfeeding structure and its determinants. Ethnic affiliation does not have any significant effect on nursing variables, and the suckling patterns of the Fulbe and Bozo women are comparable in this study. Suckling activity does not vary according to time of day, although individual women exhibit different temporal patterns of nursing behavior. Infant age is significantly and negatively correlated to session duration. As infants get older and their diets are supplemented with food other than breastmilk, their appetites decrease and, consequently, they suckle less. However, there is much individual variation in this relationship, and it is argued that the decrease in suckling due to supplementation may be offset by an increase in suckling due to infants demanding the breast for physical affection. Maternal age, in contrast, is not correlated with any nursing variable in this study. This indicates that there is no decrease in physiological capacity to provide milk and that access to surrogate caretakers is either not correlated with maternal age, or is not a strategy employed by these women. Am. J. Hum. Biol. 10:179-190, 1998. © 1998 Wiley-Liss, Inc.