Breast-feeding and post-partum amenorrhoea in Indonesia

The association between breast-feeding patterns and resumption of menses post-partum was examined in a prospective study in Indonesia. In order to examine these relationships directly in a longitudinal study, it was first necessary to distinguish among women who experienced infant mortality before menses resumed, women who weaned before menses resumed, and women who had return to menses while breast-feeding. Information on suckling patterns and menstrual status was collected by recall for 444 women at monthly visits for 2 years. Three main breast-feeding variables, minutes per episode, number of episodes per day, number of episodes per night, and other breast-feeding variables were derived for each woman, to give the average nursing pattern up to menses or the end of the study, which-ever came first. While high levels of nursing for each of these three main variables were found to be significantly related to delay in return of menses post-partum, the interactions between more minutes per episode, and more frequent day- and night-time feeds, were found to be the most important factors in the delay in onset of post-partum menstruation in those women whose menses resumed while still nursing or who remained amenorrhoeic and nursing at the end of the study.     

Nursing practices and lactation amenorrhoea

The purpose of this study is to test the hypothesis that nursing behavior is an independent underlying factor of importance in duration of amenorrhea. Multivariate analysis is applied to information on frequency and duration of nursing practices, maternal age, and nutritional status assessed by weight for height in a sample of 32 middle-class American women with a wide range of nursing behavior. The mothers were followed for 2 years postpartum, data being collected during 8 home visits by interview and by nursing records kept by the mothers. Amenorrhea lasted 1.3 to 27.1 months in the sample as a whole. Those women who nursed frequently (8/day) during exclusive breastfeeding remained amenorrheic longer than infrequent nursers, introduced supplements later, and did not resume menses as promptly thereafter. They continued an hour or more of night nursing during supplemented nursing. Duration of exclusive nursing and night nursing after supplementation were the major influences on duration of amenorrhea. This strong association favors the hypothesis that the underlying factor is nursing behavior. Mother's age, weight-for-height, and nursing frequency before supplementation showed no significant effect. Those women who introduced supplements late and maintained at least an hour of night nursing had a prolonged period of amenorrhea. The median for this group was 6-10 months longer than that for those who started supplements early and/or reduced subsequent night nursing to less than an hour. The recommendation that women must suckle their babies at least 5 times a day with a total suckling duration of more than 65 minutes per day is not sufficient. The findings reported here suggest that if women nurse exclusively for the 1st half year, maintaining night nursing after introducing supplements is important. If they supplement earlier, then they will lose the contraceptive protection of lactation, irrespective of how they nurse.     

A biobehavioral model for breastfeeding effects on return to menses postpartum in Javanese women

Abstract

This paper examines the effects of nursing behavior on the duration of lactation amenorrhea in 382 rural Indonesian women who experienced resumption of menses while breastfeeding or were breastfeeding and amenorrheic at the end of a two‐year prospective study. Three primary breastfeeding variables (number of night‐time nursing bouts, number of day‐time nursing bouts, and minutes per bout) were used to develop a behavioral model for breastfeeding. Four breastfeeding patterns were identified for these women. These were designated as: (1) low intensity, (2) medium‐low intensity, (3) medium‐high intensity, and (4) high intensity breastfeeding behavior. Menses resumed at medians of 11.2,16.0,17.6, and 20.8 months, respectively, for these groups. The relationships among the breastfeeding variables in the behavioral model and return to menses were developed and tested by life table and proportional hazards models. Ten per cent of the high intensity breastfeeding group (6 women) delayed menses between 33 and 52 weeks, while 90 per cent (56 women) postponed return of menses for over one year.     

The effect of initiation of child supplementation on resumption of post-partum menstruation

The effects of initiation of solid and liquid supplementation on resumption of post-partum menstruation are examined, using data from a 2-year prospective study of birth interval dynamics from central Java, Indonesia. The sample analysed consisted of 444 women who experienced resumption of menses while breast-feeding, women who were breast-feeding and amenorrhoeic at the end of the study, or women who resumed menstruation or were censored after infant mortality and weaning which preceded the resumption of menses. Multivariate hazard model analysis was used to assess the significance of supplementation, various breast-feeding covariates, and age and parity of the dependent variable. Because the timing of supplementation varies, the supplementation variables were introduced into the analysis as time-varying covariates. For the mothers in the sample, solid and liquid supplementation was initiated at medians of 2.1 and 8.0 months respectively. The former had a significant effect on resumption of menses, while the latter was only marginally significant. Earlier supplementation meant shorter durations of amenorrhoea for the majority of women. However, the effect was not consistent across all categories of women. For the small group of mothers who were low intensity breast-feeders (less than or equal to 6 minutes per nursing episode) or as low frequency day-time breast-feeders (less than or equal to 6 nursing episodes per day-time), earlier supplementation had no additional effect on their rate of resumption of menses post-partum.     

Nursing behaviour and its relation to duration of post-partum amenorrhoea in an Andean community

Nu?oa is a high altitude rural Peruvian community characterized by socioeconomic stratification and differential access to the market economy. Nursing practices and the effects of nursing are also stratified; this translates into a risk of menses at 12 months post-partum nearly seven times greater in wealthier than in poorer women. Most nursing occurs in the morning, among those who practice on-demand breast-feeding. Nursing episodes are clustered into sessions; the amount of breast-feeding is regulated by varying the number of episodes per session rather than by changing the duration of suckling episodes or the frequency of sessions per hour. Thus, resumption of ovulation is not dependent on the variable spacing of nursing episodes or sessions. The components of nursing activity most likely to be responsible for variation in the duration of post-partum amenorrhoea in these nursing women are mean session duration and mean number of episodes per session. The mean duration of morning nursing sessions is negatively associated with infant's age, reflecting the greater reliance of younger children on breast-milk. The mean duration of afternoon nursing sessions is positively associated with mother's age, independent of infant's age, possibly reflecting maternal age-related variation in milk production capabilities. Baby minding by older daughters may also help to explain variation in afternoon nursing.     

Postpartum lactational amenorrhoea as a means of family planning in the Sudan: a study of 500 cases

The lactational histories of 500 Sudanese women were studied retrospectively to examine postpartum lactational amenorrhea as a method of family planning. Particular attention was given to the factors affecting postpartum lactational amenorrhea, including supplementary feeding and the use of modern contraceptive methods. Breast-feeding was overwhelmingly practised (90%) among this sample, which was roughly representative of the Sudanese population as a whole. The prevalence of amenorrhea among this group of lactating women was quite high (73%). Duration of lactational amenorrhea ranged from 2 to 36 months with a median of 12 months. Introduction of supplementary feeding had little effect on lactational amenorrhea up to the 9th month of breastfeeding. Beyond the 12th month of breastfeeding, lactational amenorrhea was significantly prolonged by postponing the introduction of supplementary feeding until the 4th month or later. Ovulation, and hence conception, during lactational amenorrhea was unpredictable. It occurred as early as the 3rd or as late as the 36th month postpartum. Conceptions interrupting lactational amenorrhea soon after delivery (3-9 months) were more frequent among primiparous women. The failure rate of lactational amenorrhea as a contraceptive was 8.4%. Though extremely high compared to that of the pill, lactational amenorrhea was more useful as a fertility control mechanism because, in this study, a high proportion of women initiated pill use, but soon discontinued it because of side effects. Modern contraceptive practice was not prevalent. Amenorrheic mothers accepted the pill after the 6th month postpartum (41%, compared to lactating mothers whose menses had returned who started much earlier. 49% of the women studied relied completely on the protection of lactational amenorrhea. 57% of all lactating women who used the combined pill reported a reduction in milk production. Knowledge of modern contraception was poor and incorrect in many cases, leading to several policy implications, including usage of sterilization.     

Evolutionary perspectives on mother-infant sleep proximity and breastfeeding in a laboratory setting

Human maternal and infant biology likely coevolved in a context of close physical contact and some approximation of frequent, "infant-initiated" breastfeeding. Still, mothers and infants commonly sleep apart from one another in many western societies, indicating a possible "mismatch" between cultural norms and infant biology. Here we present data from a 3-night laboratory-based study that examines differences in mother-infant sleep physiology and behavior when mothers and infants sleep together on the same surface (bedsharing) and apart in separate rooms (solitary). We analyze breastfeeding frequency and interval data from the first laboratory night (FN) for 52 complementary breastfeeding mothers and infants (26 total mother-infant pairs), of which 12 pairs were routine bedsharers (RB) and 14 were routine solitary sleepers (RS). RB infants were 12.0 ± 2.7 (SD) weeks old; RS infants were 13.0 ± 2.4 weeks old. On the FN, RB mother-infant pairs (while bedsharing) engaged in a greater number of feeds per night compared to RS (while sleeping alone) (P < 0.001). RB also showed lower intervals (min) between feeds relative to RS (P < 0.05). When we evaluated data from all three laboratory nights (n = 36), post hoc, RB breastfed significantly more often (P < 0.01) and showed a trend towards lower intervals between feeds (P < 0.10). Given the widely known risks associated with little or no breastfeeding, the demonstrated mutually regulatory relationship between bedsharing and breastfeeding should be considered in future studies evaluating determinants of breastfeeding outcomes.     

Variability of breast sucking, associated milk transfer and the duration of lactational amenorrhoea.

Quantitative relationships between physical parameters of sucking, milk transfer and the duration of amenorrhoea were examined in normal mother-baby pairs under exclusive breastfeeding. Sucking pressures were recorded twice on the second and once on the fifth month after birth, during complete breastfeeding episodes, by means of a catheter attached to the nipple and connected to a pressure transducer, the signals of which were analysed by computer. Babies were weighed before and after each sucking episode to estimate milk transfer. In the first nursing episode after noon, 2-month-old babies sucked from 140 to > 800 times during 4-15 min from the first breast, obtaining from 20 to > 100 g milk. The physical parameters of sucking and milk transfer exhibited high inter-individual but low intra-individual variabilities. There were significant differences in the physical parameters of sucking and milk transfer efficiency between first and second breast and between the second and fifth months after birth. Milk transfer efficiency was inversely correlated with time occupied by non-sucking pauses > or = 1.5 s, and was directly correlated with mean intersuck intervals in the first breast and with duration of the sucking episode, number of sucks, mean pressure and area under the pressure curve in the second breast. There was no correlation between the physical parameters of sucking and duration of lactational amenorrhoea (n = 62). However, significantly more mothers had amenorrhoea lasting > 180 days among those whose babies spent a longer proportion of the nursing episode in non-sucking pauses > or = 1.5 s. This finding indicates that sensory stimulation of the nipple produced during a nursing episode by stimuli other than sucking itself may have an important role in sustaining lactational amenorrhoea. It is concluded that nursing episodes have a complex structure that allows the development of a breastfeeding phenotype in each mother-baby pair, exhibiting important inter-individual variability. The present analysis does not support the contention that this source of variability accounts for the variability in the duration of lactational amenorrhoea.     

A comparison of the effects of suckling or transient dopamine antagonism on thyrotropin-releasing hormone and suckling induced prolactin release in lactating rats

Prolactin (PRL) release was studied in mid-lactational female rats by comparing the stimulatory influence of suckling to a drug protocol that mimics the effect of suckling on the anterior pituitary (AP). Animals that nursed pups for 15 minutes and were allowed to suckle again 60 minutes later for 10 minutes, released PRL effectively during both nursing episodes; however, in animals that received the dopamine (DA) agonist 2-Br-alpha-ergocryptine maleate (CB-154, 0.5 mg/rat i.v.) at the end of the first nursing period did not show an increase in plasma PRL to a second suckling stimulation by the pups. When thyrotropin releasing hormone (TRH) was substituted for the second suckling period in CB-154 treated rats, a slight increase in plasma PRL occurred 5 minutes after the injection. In a third study we transiently blocked the action of DA at the AP by injecting the DA antagonist domperidone (0.01 mg/rat i.v.), followed 5 minutes later by the administration of CB-154. One hour later animals were either allowed to suckle pups for 10 minutes or were injected with TRH. Treatment with TRH resulted in an 11 fold increase in plasma PRL but suckling was completely ineffective in inducing PRL release. These data suggest that the lack of PRL release to suckling in CB-154 treated rats was due to inhibitory effects of CB-154 on neural mechanisms which link nursing to PRL release. In addition, the data show that pharmacologic DA antagonism affects TRH releasable PRL more than does suckling. This may be due to a reduction, by suckling, of the pool of PRL that is available to be released by TRH administration.     

Postpartum amenorrhoea in Ethiopia: The role of weaning,child death,and socioeconomic factors

Abstract

Using data from the 1990 National Family and Fertility Survey (NFFS) and employing discrete‐time hazards models, we examine the effect of weaning, child death, and socioeconomic factors on postpartum amenorrhoea in Ethiopia. The results show that 91 in every 100 mothers breastfed their child for at least 6 months. The median duration of breastfeeding stands at 18 months, and amenorrhoea lasts for a median duration of 12 months. Significant variations in breastfeeding and amenorrhoea duration are also observed among the different categories of breastfeeding women. The median duration of breastfeeding for lactating women is 24 months, 6 months for those who weaned, and 2 months for those whose child died. The median duration of postpartum amenorrhoea is 14 months for breastfeeding women, 12 months for those who weaned, and 6 months for those whose child died. Discrete‐time hazard models reveal that child death has the strongest effect on the resumption of menses. Net of other factors, the risk of returning to menses increased 3 times for mothers whose child died. The effect of child death, however, decreases over time. Weaning also has a significant positive effect; and, like child death, its effect diminishes as time passes. The study further shows significant differences in the risk of returning to postpartum menses by socioeconomic characteristics of the women, even though they are breastfeeding.     

Litter Size Determines Circadian Periodicity of Nursing in Rabbits

Nursing in rabbits occurs inside the nest with circadian periodicity. To determine the contribution of suckling stimulation in regulating such periodicity, we varied the size of the litters provided (1, 2, 4, or 6–8 pups). Nursing does, kept under a 14:10 (L:D) photoperiod, were continuously videotaped from parturition into lactation day 15. Although parturitions occurred throughout the day, a significant negative linear correlation (p?<?0.0001; r?=??0.68) was evident between time of delivery and time of nursing on lactation day 1, regardless of newborn number: longer intervals between these two events were seen in does delivering in the early morning than in those that gave birth late in the day. In rabbits suckling 6–8 pups, a Rayleigh analysis revealed that the population vector best describing their nursing pattern (across lactation days 1–15) had a phase angle?=?58° (corresponding to solar time 0352?h and rho?=?0.78; p?<?0.001). In contrast, the nursing pattern of does nursing litters smaller than 6 pups did not show circadian periodicity; rather, mothers showed multiple entrances into the nest box throughout the day. Cluster analysis revealed that the main equilibrium point of intervals between suckling bouts shifted from 24?h (6–8 pups) to 6?h (4 and 2 pups) and to as low as 4?h with 1 pup. In the groups nursing 2, 4, or 6–8 pups, most nursing episodes were followed by food and water intake. Those mothers also showed self-grooming of the ventrum and nipples after nursing. The incidence of these behaviors was lower in does nursing 1 pup. In conclusion, nursing in rabbits spontaneously occurs with circadian periodicity, but it is largely modulated by a threshold of suckling stimulation. (Author correspondence: gabygmm@gmail.com)     

Observations of maternal-infant interactions in a captive herd of sable antelope (Hippotragus niger)

The New York Zoological Society's captive-breeding program on St Catherine's Island, Georgia, includes a herd of sable antelope (Hippotragus niger). Two aspects of mother-infant interactions, nursing and hiding, are described herein. Three younger calves, up to 6 d of age, and three older calves, 8 to 50 d of age, were the subjects of focal-animal and continuous observations and instantaneous time-point samples. Two of the younger calves were born to multiparous cows. One cow was primiparous. Between the three calves, quantitative differences in nursing episodes were found in the mean duration (1.7–3.6 min), mean number per d (1.0–8.6 episodes), and mean total time per d (2.6–14.6 min). Despite these differences, all calves thrived. The multiparous cows exhibited a pattern described in captive and wild ungulates: approaching their calves prior to nursing before the calves emitted any response; and nursing their calves early and late in the day. The cows also exhibited nursing-time synchrony. Three instances of calves suckling younger calves' mothers are also described. Two new interpretations of the function of hiding behavior are offered: (1) If older calves exploit the inexperience of newborn calves by nursing from their mothers, then younger calves may benefit by hiding out of the view of other herd members. Hiding behavior may result from intercalf competition; and (2) if newborns vacillate between arousal-increasing and arousal-reducing activities, then “hider” species may hide to attain arousal-reduction.     

The role of bacteria in lactational mastitis and some considerations of the use of antibiotic treatment

Background

The proportion of mothers in Japan who breastfeed exclusively has been low since the 1970s. The purpose of this study was to examine the association between the time of first breastfeed after birth and the proportion of mothers fully breastfeeding up to four months postpartum.

Methods

A survey was conducted using a self-administered questionnaire. The participants were 318 mothers who participated in a physical examination of their four month old infants in Nagasaki City, Japan in 2003.

Results

The time of first breastfeeding up to 120 minutes was significantly associated with the proportion of mothers fully breastfeeding during their stay in the clinic/hospital (p = 0.006), at one month (p = 0.004) and at four months after birth (p = 0.003). There was no significant difference in the proportion of full breastfeeding in mothers who first breastfed between the period of less 30 minutes after birth and that of between 31 and 120 minutes after birth. Logistic regression analysis indicated that the proportion of mothers who continued full breastfeeding at four months was significantly higher in those who breastfed their baby within 120 minutes compared with more than 120 minutes (OR 2.5, p = 0.01), but was not significantly different in those who breastfed within 30 minutes compared with more than 30 minutes (OR 1.8, p = 0.06). Early breastfeeding was affected by caesarean section, premature delivery and severe bleeding during delivery.

Conclusion

Commencement of early breastfeeding was associated with the proportion of mothers who fully breastfed their infants up to four months. Early breastfeeding, especially within two hours, is recommended for child and maternal health.     

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.     

Effect of supplementary food on suckling patterns and ovarian activity during lactation.

Patterns of infant feeding, basal prolactin concentrations, and ovarian activity were studied longitudinally in 27 breast-feeding mothers from delivery until first ovulation. Suckling frequency (6.1 feeds/day) and suckling duration (122 mins/day) reached peak values four weeks post partum and remained relatively constant until the introduction of supplementary food at a mean of 16 weeks post partum. There were subsequently sharp declines in both the frequency and duration of suckling, both of which correlated closely with basal prolactin concentrations. None of the 27 mothers ovulated during unsupplemented breast-feeding, but within 16 weeks of introducing supplements ovarian follicular development had returned in 20 and ovulation in 14 mothers. The mothers who ovulated within 16 weeks of giving supplements had reduced frequency and duration of suckling more quickly and weaned more abruptly than those who continued to suppress ovulation. These data suggest that the introduction of supplementary food may exert an important and hitherto unrecognised effect on the timing of first ovulation by reducing the frequency and duration of suckling episodes.     

A qualitative study investigating the barriers to returning to work for breastfeeding mothers in Ireland

Background

The World Health Organization (WHO) recommends that mothers exclusively breastfeed for the first 6 months of an infant’s life. In Ireland, currently paid maternity leave is 26 weeks and the expectant mother is required by law to finish work 2 weeks before her expected delivery date. Mothers wishing to exclusively breastfeed for 6 months or longer find themselves having to take holiday leave or unpaid leave from work in order to meet the WHO’s guidelines. The aim of this study is to explore women’s experiences of breastfeeding after their return to work in Ireland.

Methods

This study was carried out utilizing a qualitative design. Initially 25 women who returned to the workforce while continuing to breastfeed were contacted, 16 women returned consent forms and were subsequently contacted to take part in an interview. Interviews were recorded and transcribed verbatim and thematic analysis was employed to establish recurring patterns and themes throughout the interviews.

Results

Women noted that cultural attitudes in Ireland coupled with inadequate or inconsistent advice from health professionals posed the biggest challenge they had to overcome in order to achieve to 6 months exclusive breastfeeding. The findings of this study illustrate that mothers with the desire to continue to breastfeed after their return to work did so with some difficulty. Many did not disclose to their employers that they were breastfeeding and did not make enquiries about being facilitated to continue to breastfeed after their return to the workplace. The perceived lack of support from their employers as well as embarrassment about their breastfeeding status meant many women concealed that they were breastfeeding after their return to the workplace.

Conclusion

While it has been suggested that WHO guidelines for exclusive breastfeeding for 6 months may be unattainable for many women due to work commitments, a different problem exists in Ireland. Mothers struggle to overcome cultural and societal obstacles coupled with inadequate support from health professionals. Encouraging and facilitating women to continue to breastfeed after they return to work will help to normalise breastfeeding within Irish culture and promote continued breastfeeding as a viable option for working mothers.

     

Distribution of postpartum amenorrhea in rural Bangladeshi women

Previous studies of postpartum amenorrhea (PPA) demonstrated distinct subgroups of women with short and long durations of amenorrhea. This phenomenon was attributed to cases where breastfeeding is absent because of pregnancy loss or infant death, or confusion of postpartum bleeding with resumption of menses. We explored these ideas using data from an 11-month prospective study in Bangladesh in which 858 women provided twice-weekly interviews and urine specimens for up to 9 months; 300 women were observed while experiencing PPA. The resulting exact, interval-censored, or right-censored durations were used to estimate parameters of two-component mixture models. A mixture of two Weibull distributions provided the best fit to the observations. The long-duration subgroup made up 84% (+/- 4% SE) of the population, with a mean duration of 457 (+/- 31) days. The short-duration subgroup had a mean duration of 94 (+/- 17) days. Three covariates were associated with the duration of PPA: women whose husbands had high-wage employment had a greater probability of falling in the short-duration subgroup; women in the long-duration subgroup whose husbands seasonally migrated had shorter periods of PPA within the subgroup; and mothers in the short-duration subgroup who gave birth during the monsoon season experienced a shortened duration of PPA within the subgroup. We conclude that the bimodal distribution of PPA reflects biological or behavioral heterogeneity rather than shortcomings of data collection.     

Reasons given by mothers for discontinuing breastfeeding in Iran

Background

We have previously shown that in Iran, only 28% of infants were exclusively breastfed at six months, despite a high prevalence of breastfeeding at two years of age. The primary aim of this study was to investigate the reasons women discontinued exclusive breastfeeding.

Method

This retrospective study was based on questionnaires and interviews with 63,071 mothers of infants up to 24?months of age, divided into two populations: infants younger than six months and six months or older. The data were collected in 2005?C2006 from all 30 provinces of Iran.

Results

Only 5.3% of infants less than six months of age stopped breastfeeding (mean age of 3.2?months); more commonly in urban than rural areas. The most frequently cited reasons mothers gave for discontinuing exclusive breastfeeding were physicians?? recommendation (54%) and insufficient breast milk (self-perceived or true, 28%). Breastfeeding was common after six months of age: only 11% of infants discontinued breastfeeding, at a mean of 13.8?months. The most common reason for discontinuation at this age was insufficient breast milk (self-perceived or true, 45%). Maternal illness or medication (10%), infant illness (6%), and return to work (3%) were uncommon causes. Use of a pacifier was correlated with breastfeeding discontinuation. Maternal age and education was not associated with duration of breastfeeding. Multivariate analysis showed that using a pacifier and formula or other bottle feeding increased the risk of early cessation of breastfeeding.

Conclusions

Physicians and other health professionals have an important role to play in encouraging and supporting mothers to maintain breastfeeding.     

A case of adoption and allonursing in captive plains zebra (Equus burchellii)

Although allonursing (allowing non-filial offspring to suckle) can be a costly behaviour, it has been reported for many mammals including ungulate species. However, such behaviour is very rare in equids. This is the first report on adoption and allonursing in captive plains zebra (Equus burchellii), recorded in the Dv?r Králové Zoo, Czech Republic. We observed a case of adoption of an orphaned foal by a lactating mare, who then regularly nursed two foals (filial and non-filial). The allonursing mare rejected more suckling attempts, terminated suckling bouts more often, and had a shorter suckling bout duration than other mares. When nursing both foals at the same time, the suckling bout lasted for less time than when nursing a single foal, regardless of whether it was filial or non-filial. The allonursing mare apparently did not discriminate between the filial and non-filial foal.     

Major role of suckling stimulation for inhibition of estrous behaviors in lactating rabbits: acute and chronic effects

Lactation in rabbits induces anestrus: sexual receptivity and scent-marking (chinning) are reduced despite the brevity of suckling (one daily nursing bout, lasting around 3 min). The mechanisms underlying this effect are unknown but, as chinning, lordosis, and ambulation in an open field are immediately inhibited by the peripheral stimulation received during mating we hypothesized that, across lactation, suckling stimulation would provoke a similar effect. To test this possibility we provided litters of 1, 3, 5, or 10 pups across lactation days 1-15 and quantified chinning and ambulation frequencies, the lordosis quotient, and milk output. Baseline chinning frequency, determined before the daily nursing bout, was low across lactation days 1-15 in does nursing 3, 5 or 10 pups but it increased steadily across days 1-10 in rabbits suckling one pup. Yet, a single young was sufficient to abolish chinning for about 1h, after which this behavior rose again. Suckling litters of all sizes reduced (but did not abolish) ambulation frequency, both chronically (baseline levels declined across days 1-5) and acutely. Sexual receptivity was significantly reduced on lactation day 15 only in does that had nursed 10 pups. Large litter size promoted a larger milk output and a normal duration of nursing episodes. Results support a major role of suckling stimulation for the suppression of estrous behaviors and ambulation through as yet unidentified mechanisms.