The influence of reproductive experience on milk energy output and lactation performance in the grey seal (Halichoerus grypus)

Although evidence from domestic and laboratory species suggests that reproductive experience plays a critical role in the development of aspects of lactation performance, whether reproductive experience may have a significant influence on milk energy transfer to neonates in wild populations has not been directly investigated. We compared maternal energy expenditures and pup growth and energy deposition over the course of lactation between primiparous and fully-grown, multiparous grey seal (Halichoerus grypus) females to test whether reproductive experience has a significant influence on lactation performance. Although there was no difference between primiparous females in milk composition and, thus, milk energy content at either early or peak lactation primiparous females had a significantly lower daily milk energy output than multiparous females indicating a reduced physiological capacity for milk secretion. Primiparous females appeared to effectively compensate for lower rates of milk production through an increased nursing effort and, thus, achieved the same relative rate of milk energy transfer to pups as multiparous females. There was no difference between primiparous and multiparous females in the proportion of initial body energy stores mobilised to support the costs of lactation. Although primiparous females allocated a greater proportion of energy stores to maternal maintenance versus milk production than multiparous females, the difference was not sufficient to result in significant differences in the efficiency of energy transfer to pups. Thus, despite a lower physiological capacity for milk production, primiparous females weaned pups of the same relative size and condition as multiparous females without expending proportionally more energy. Although reproductive experience does not significantly affect the overall lactation performance of grey seals, our results suggest that increases in mammary gland capacity with reproductive experience may play a significant role in the age-related increases in neonatal growth rates and weaning masses observed in other free-ranging mammals.     

Alloparenting in Steller sea lions (<Emphasis Type="Italic">Eumetopias jubatus</Emphasis>): correlations with misdirected care and other observations

Alloparental care is rarely observed in Steller sea lions (Eumetopias jubatus) where maternal care is extended to a single pup for up to 1 year or more. However, we observed 28 allonursing events and one case of adoption at a small breeding rookery in the western Gulf of Alaska between the years 2001 and 2005. Multiparous and primiparous females were observed nursing nonfilial individuals with equal frequency, but primiparous females spent significantly more time nursing nonfilial individuals. Multiparous females allowed allonursing only while sleeping and unaware while most primiparous females were aware that they were allonursing. These results are consistent with the misdirected-care hypothesis suggesting that primiparous (presumably younger) females nurse nonfilial pups due to inexperience, whereas multiparous (presumably older) females are victims of milk stealing during times of inattentiveness. Nonfilial pups were aggressively tossed most often during the pupping season and only by multiparous females, while allonursing events occurred more frequently after the pupping season. Starveling pups were not cared for by any female, but two were attended by a single bull during separate autumn seasons.     

Parity-associated reductions in behavioral sensitivity to opiates

Behavioral and physiological responses differ between primiparous and multiparous female rodents. Specifically, multiparous females respond with the full repertoire of maternal behaviors much more rapidly and with greater intensity than their primiparous counterparts. Since opiates inhibit the expression of maternal behavior in postpartum rats and can be reversed by means of the opiate antagonist naloxone, we investigated whether multiparous females would be resistant to the inhibitory effects of opiates on maternal behavior, relative to primiparous females. In Experiment 1 we evaluated the effects of a range of doses of morphine sulfate (MS; 0.625, 1.25, 2.5, 5.0, and 10.0 mg/kg or saline) on maternal behavior in primiparous females on Days 5-6 of lactation. The 5.0 and 10.0 mg/kg doses effectively disrupted maternal behavior, whereas the lower doses were ineffective or only marginally disruptive. In Experiment 2, age-matched female rats were timed-mated and tested for maternal behavior from Day 5 to 13 of lactation, after daily injections of the 5.0 mg/kg dose of MS. On Day 5 of lactation, this morphine treatment eliminated full maternal behavior in 87% of the primiparous animals, but only 37% of the multiparous animals were affected. By Day 10 of lactation, 100% of the multiparous females displayed full maternal behavior after MS treatment, whereas only 69% of primiparous females were responsive. In Experiment 3, analgesic responses were measured both in rats experiencing their initial or second pregnancy, and in postpartum, lactating rats after MS (5.0 mg/kg) administration. Using a tail-flick apparatus to measure analgesia, we found multigravid females to be significantly less analgesic prepartum than primigravid females, suggesting less sensitivity to endogenous opioids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differences in fertility and suckling patterns between primiparous and multiparous rhesus mothers (Macaca mulatta)

Primiparous females gave birth around the same time as multiparous nonlactating females, and earlier than did multiparous lactating females. No differences in birth sex ratio were found between primiparous and multiparous females. During the breeding season following birth, primiparous mothers returned to oestrus later than did multiparous mothers, and while few primiparous mothers conceived successfully during that season, most multiparous mothers did. Primiparous females suckled their infants more frequently than did multiparous females at all ages; infants of primiparous females also made more nipple contacts per bout, and had shorter sucking bouts. When mothers came into oestrus, suckling frequency drastically increased for primiparous females, but not for multiparous females, magnifying the differences between the two groups. After the first oestrus, suckling frequency declined for all mothers, but multiparous mothers had consistently lower suckling frequencies than did primiparous mothers. The high suckling frequency, and numerous nipple contacts per bout, found among primiparous mothers are likely to be related to the low reproductive chances that these females faced during the breeding season. Multiparous mothers seemed to compensate for their low suckling frequency by lengthening the suckling bouts, and this suckling pattern did not hinder their reproduction. It is argued that primiparous mothers might have to suckle their infants more frequently because they can only produce milk at slow rates, being in this way forced into a reproductively inhibiting suckling pattern. However, the delay in subsequent reproduction could be ultimately advantageous for primiparous mothers if it enhanced infant survival, and allowed the mothers to regain physical condition before reproducing again.     

Do Laboratory Mouse Females that Lose Their Litters Behave Differently around Parturition?

Efficiency in laboratory mouse breeding is hampered by poor reproductive performance, including the loss of entire litters shortly after birth. However, the underlying mechanisms are not yet fully understood and establishing the cause of death in laboratory mouse pups can be complicated. Newborn mouse pups are generally hidden in nests, dead pups are often eaten by the female, and the widespread practice of leaving periparturient females undisturbed complicates inspection, which may delay the discovery of pup loss. In order to efficiently prevent problems with litter loss, it is important to find key factors for survival. We investigated differences in periparturient behavior between female laboratory mice whose pups survived until weaning and females whose entire litters were lost. Video recordings of 82 primiparous females of the C57BL/6 strain or knockouts with C57BL/6 background were used. The mice were observed from 24 h before until 24 h after parturition and female behaviors coded using a pre-established ethogram. The relationship between behavior and survival was analyzed using logistic models, where litter survival was regressed on the proportion of 30-s observations with at least one occurrence of the behavior. We found that females with surviving litters performed more nest building behavior during the last 24 h before parturition (p = 0.004) and spent less time outside the nest during the entire observation period (p = 0.001). Increased litter survival was also associated with more passive maternal behaviors and the female ignoring still pups less. Females that lost their litters performed more parturition-related behaviors, suggesting prolonged labor. The results indicate that maternal behavior plays a significant role in laboratory mouse pup survival. Complications at parturition also contribute to litter mortality.     

Mass changes of grey seal Halichoerus grypus pups on Sable Island: differential maternal investment reconsidered

Theory predicts that where variance in reproductive success differs between sexes, as in many sexually dimorphic species, mothers should invest more in male than in female offspring. In pinnipeds, parental investment is the sole responsibility of the mother. Both size at birth and subsequent mass gain during lactation are measures of that investment. We studied mass gain of grey seal pups, a sexually dimorphic species, during lactation and mass loss during the first 13 days of the postweaning fast using longitudinal data obtained on Sable Island, Canada. A mixed-effects repeated measures model was used to account for the serial correlation in these longitudinal data. We found no significant difference in the birth mass of male (16.6 ± 0.45 kg) and female (15.6 ±0.74 kg) pups. Rate of mass gain by males (3.0 ± 0.13 kg/d) and females (2.7 ± 0.12 kg/d) also did not differ significantly during the lactation period. Grey seal pups on Sable Island tended to be larger at birth and gain mass more rapidly (70%–100%) during lactation than those in the United Kingdom. Mass loss of weaned pups was curvilinear over time. Over the first 10 days of the fast, pups lost 22% of their weaning mass. In both males and females, large pups lost mass more slowly than small ones during the postweaning fast. Based on our results and a review of previous studies, we found little evidence of differential maternal investment in male and female grey seal pups.     

Maternal behaviour and early behavioural ontogeny of grey seals (Halichoerus grypus) on the Isle of May, UK

Female grey seals allocated more resources to individual sons than to individual daughters. Mothers of male pups spent significantly larger proportions of their time defending and feeding their young than did mothers of female pups. The amount of time females spent ashore and the proportion of time spent in various behavioural states was influenced by the habitat of the birth site and the age of the pup.
Grey seal neonates spent the majority of their time prone and immobile, perhaps to allow maximum energy retention (maximum mass gain) and to facilitate mothers relocating their pups. The proportion of time pups spent in the various behavioural states was influenced by the whelping habitat. Pups became increasingly active with age. Males were significantly more aggressive than females and, at one site they performed nosing behaviour with their mothers significantly more often than did female neonates.     

Reproductive experience and opioid regulation of luteinizing hormone release in female rats

The objective of the present study was to determine whether reproductive experience that produces shifts in opioid regulation of prolactin secretion and behavioural functions also alters opioid regulation of LH during the oestrous cycle or lactation. In Expt 1 the effect of naloxone administration (i.v.) on LH was compared between age-matched, nulliparous and primiparous, catheterized female rats on dioestrus II. In Expt 2, the effects of multiple reproductive experiences on opiate control of LH were investigated using cyclic, nulliparous and multiparous (three litters) rats. In both experiments, no differences in naloxone-stimulated LH release were found between groups even though multiple reproductive experiences resulted in the prolongation of oestrous cyclicity. In Expt 3, day 8 lactating primiparous rats were administered 2, 5, 10 or 25 mg naloxone kg-1 i.v. The three lowest naloxone doses, but not the 25 mg kg-1 dose, significantly increased LH concentrations. The possible effects of prior reproductive experience on opioid control of LH during lactation were then investigated. Naloxone at 0.5 mg kg-1, but not at 2 mg kg-1 or 10 mg kg-1, stimulated a significantly greater rise in LH in multiparous (two litters) than in primiparous females. Overall, these data indicate that while modest differences were found in naloxone-induced LH responses between multiparous and primiparous animals during lactation, reproductive experience did not significantly alter opioid regulation of LH during subsequent oestrous cycles at the naloxone doses examined. Hence, the effects of reproductive experience on opioid regulation of LH are less pronounced than those previously found for opioid regulation of prolactin and behaviour.     

Reproductive performance in grey seals: age-related improvement and senescence in a capital breeder

1. Three hypotheses have been advanced to account for age-related improvement in performance: the selection hypothesis predicts improved due to the loss of lower quality phenotypes, the constraint hypothesis predicts individuals improve function, and the restraint hypothesis predicts younger individuals forego or reduce effort because of mortality risks. A decline in age-related performance (i.e. senescence) is predicted by mutation accumulation, antagonistic pleiotropy and disposable soma (wear and tear) hypotheses. 2. Using five measures of performance - birth rate, maternal and pup birth mass, pup weaning mass, weaning success and lactation length - we tested these hypotheses concerning age-related change in reproduction in 279 female grey seals (Halichoerus grypus), ages 4-42 years, over a 23-year period between 1983 and 2005 on Sable Island, Nova Scotia. These females produced 2071 pups. 3. Although body mass of primiparous females increased with age (4-7 years) birth mass of their pups did not, but pup weaning mass did. Second- and third-parity females of the same age as primiparous females gave birth to and weaned heavier pups. However, parity and age were dropped from models when maternal body mass was included. 4. The proportion of females giving birth varied significantly with maternal age, increasing in young females and then declining late in life. Weaning success rate also increased rapidly to about 8 years and subsequently declined in females > 32 years. 5. Generalized additive models indicated nonlinear changes in 3 day body mass (i.e. approximately birth mass) and weaning mass of pups as a function of maternal age, after accounting statistically for the effects of maternal body mass. Mixed-effects, repeated-measures models fitted to longitudinal data further supported the conclusion that pup birth mass and weaning mass vary nonlinearly with maternal age and indicated nonlinear changes in lactation duration. 6. We found some support for the constraint hypothesis, but our findings were not consistent with the selection hypothesis or the restraint hypothesis as the basis for improvement in reproductive performance. 7. Senescence was evident in multiple female and offspring traits, indicating the degeneration in function of several physiological systems as predicted by the disposable soma hypothesis.     

A comparison of primiparous and multiparous mother-infant dyads inMacaca mulatta

The relationships of 42 rhesus monkey mother-infant dyads were examined to investigate the effects of the mothers' parity. Primiparous mothers were found to be younger, more excitable and less confident than the multiparous mothers. They also received more aggression from other adult females living in their social group and were more anxious about their infants, approaching and leaving them more frequently. The primiparous mothers protected their daughters more than the multiparous mothers and their daughters correspondingly spent more time in the ventro-ventral position and more time on the nipple. Their sons however spent less time in contact with their mothers than did the sons of the multiparous mothers. Although the primiparous mothers protected their daughters more than their sons, for the multiparous mothers the converse was true and sons received more maternal protection. It is suggested that the greater protectiveness of the multiparous mothers towards male infants may be a consequence of the interest siblings have in males, whereas the greater protectiveness of primiparous mothers to daughters may stem from their greater vulnerability to attacks from adult females. The importance of mother-mediated sibling influences may explain the lack of strong parity differences in previous studies.     

Inter-sexual differences in Antarctic fur seal pup growth rates: evidence of environmental regulation?

We investigated the variation of Antarctic fur seal (Arctocephalus gazella) pup growth rates in response to sex, breeding season and duration of both maternal foraging trip and attendance bouts. Data were collected during five consecutive rearing seasons at Cape Shirreff, the most important breeding colony in the South Shetland Islands, Antarctica. Our results showed significant interannual and sexual variations in pup growth rates. Male pups grew significantly faster than female pups during 2000, 2001, 2002 and 2004 seasons, whilst during 2003 no difference was found. The interannual variation in pup growth rates was correlated with the interannual fluctuation in maternal foraging trip and attendance bouts. There was a significant effect of pup sex and maternal foraging trip duration on pup growth rates, which varied between years having foraging trip duration a major effect during 2003, when females spent more time at sea and interestingly on that year there were no sexual differences in pup growth rates. The effect of attendance bout on pup growth rates was not significant. Diet analysis showed that Antarctic krill (Euphausia superba) was the most frequent prey item during the study period. Analysis of krill size distribution showed a significant difference in krill length, during 2003, when A. gazella preyed upon the smallest sizes of krill. In this study, sex was the most important factor on pup growth rates, but when prey availability seemed more limited, there are longer foraging trips and shorter attendance bouts the sex factor became less significant.     

Comparison of the "nursing" and other parental behaviors of nulliparous and lactating female rats

Virgin female rats display maternal behaviors after continuous exposure to pups (sensitization) that are in some respects similar to those of postpartum females. We herein provide a detailed comparison of the "nursing" and other parental behaviors of maternally sensitized virgin females and postpartum lactating dams. Ovariectomized and intact virgin females were exposed to pups until displaying maternal behavior. On the females' fourth day of maternal responsiveness, the pups were removed for 3 h and then returned, and subject-litter interactions were observed for 45 min. Behavior of maternal virgins was compared with that of lactating dams observed on day 4 postpartum interacting with either suckling pups or pups unable to suckle due to perioral anesthesia. Ovariectomy had no effect on behavior of virgins. Retrieval and licking of pups were deficient in virgins compared with lactating dams. Suckled dams showed prolonged kyphosis (upright crouched nursing), whereas nonsuckled dams displayed little kyphosis but rather were often in a hunched position over pups. Some aspects of quiescent "nursing" behaviors of virgins were surprisingly similar to those of suckled dams, including the latency to and duration of quiescence. Nonsuckling pup stimulation elicited more kyphosis in virgins than in lactating dams, which was still much less than in suckled dams. Virgins also "nursed" pups in hunched and prone postures. Differences between sensitized and postpartum females in their maternal behaviors likely reflect differences in motivation as well as sensory inputs they receive from pups. In particular, sensory regulation of "nursing" behaviors is influenced by reproductive state because nonsuckling pups elicit different postural responses in sensitized and lactating mothers.     

Kin Recognition and Maternal Care under Restricted Feeding in House Mice (Mus domesticus)

This study tests the hypothesis that female house mice (F1 generation of wild caught Mus domesticus) should preferentially invest in own offspring if confronted with young of different degrees of relatedness. The maternal behaviour of females with litters of 4 own and 4 unrelated alien young (cross-fostered at day 1 of lactation) was analysed during a lactation period of 22 days both under ad libitum and under restricted feeding (food was restricted by 20%). Cross-fostering and restricted feeding had no effect on the amount of time spent nursing until weaning. Under both feeding conditions the females did not differ in their maternal behaviour towards own and alien young: there were no significant differences either in the amount of time spent nursing own versus alien pups or in the time spent licking own versus alien young. Weight gain of own and alien = wild littermates did not differ significantly in mixed litters and was similar both under ad libitum and under restricted feeding. Such indiscriminate behaviour might be adaptive if female house mice prefer to communally nest with a relative and thus improve their inclusive fitness by investing in own and related offspring in a communal nest. Under moderate restricted feeding females could not wean the entire litter but reduced litter size by cannibalizing on average 2.7 pups (75% of the pups were killed when they were 4–8 days old). Females with cross-fostered litters killed as many own as alien young. This suggests that females cannot discriminate between own and unrelated young if cross-fostering takes place at day 1 of lactation. Besides testing kin recognition abilities, the experiments also allow analysis of the weaning strategy of females under food shortage. Under restricted feeding, body weight of the females was significantly lower during middle lactation than under ad libitum feeding. Weaning weight of young in reduced litters under food restriction (9–10 g) did not differ significantly from weaning weight of young in litters of 7–10 young, but was lower than that of young in similar sized litters (litter size 6), under ad libitum feeding. The maternal behaviour of cannibalizing some young under food shortage can be interpreted as a weaning strategy which results in the largest number of offspring that can be raised to a minimal weaning weight of 9–10 g. Such a weaning strategy might represent a favourable trade-off between number and size of young produced.     

Maternal investment and reproductive success in Chinese water deer

Among cervids, maternal investment, estimated as the amount of resources and care allocated to the offspring, was expected to be related to species body size. Therefore, maternal investment in a herd of captive Chinese water deer Hydropotes inermis, a relatively small species of cervid, was investigated over 3 years. Except during the lactation period, reproductive females spent about 2-fold more time resting than feeding. During lactation, the amount of time spent feeding increased highly (25.3 min/h during lactation vs 17.3 min/h during the gestation period). Females spent less than 30% of time in communal behaviours with offspring. They did not reject alien fawns during this care period. Frequency and duration of suckling events decreased exponentially from the second week onwards. More than 10% of suckling bouts were non-filial. Prenatal investment leads to a mean litter mass (about 12% of maternal mass) higher than in most cervid species. Postnatal investment in fawns represents a daily mass gain of ca. 85 g/d during the first 2 weeks, without any sexual difference. Female production, timing and synchrony of births and survival of fawns characterized reproductive success. Seventy percent of mature females gave birth, with a mean of 1.9 offspring per female. The sex ratio was even. Births were synchronous, 80% of births occurring in 25 days. In this herd, 0.74 fawn per female was successfully weaned and 0.56 fawn per female survived through their first year. Based on these results we conclude that reproductive strategy of Chinese water deer was efficient and characterized by mother-offspring relationships typical of hiders and high levels of pre- and postnatal investments. This strategy seems typical of small species of cervids without marked sexual dimorphism.[Current Zoology 55(2):102-110,2009].     

Nursing parameters in captive killer whales (Orcinus orca)

We examined nursing behaviors for a population of captive‐born killer whales (four females, three males) at SeaWorld parks from birth until 90 days of age. Nursing parameters examined included cumulatives of suckles per day, bouts per day, and suckle duration (seconds) per day. Daily cumulatives of all nursing parameters peaked within the first 2 days after birth then decreased through time. For the ages from birth until 42 days, data were converted using log_e‐log_e transformations to allow linear regression modeling. Since these parameters were characterized by autocorrelation, bootstrapping was used to obtain parameter estimates for comparisons between sexes and cow parity. Both males and females, as well as calves born to primiparous and multiparous cows, exhibited similar nursing patterns. However, there were statistically significant differences (α < 0.05) between the regression equations among most of the nursing parameters examined. Cumulative frequencies and amounts from birth through 42 days of age for all nursing parameters were examined. Means were statistically similar (α > 0.05) between genders (means[sd] for males and females, respectively; suckles 3,772.7[412.4] and 3,276.3[1,226.5]; bouts 1,238.3[189.0] and 1,103.3[96.4]; suckle duration [seconds] 28,990.7[5,861.9] and 29,233.0[5,255.0]) and cow parity (means[sd] for primiparous and multiparous, respectively; suckles 4,459.0[606.7] and 3,101.0[753.8]; bouts 1,240.0[243.3] and 1,129.6[116.2]; suckle duration [seconds] 32,415.0[5,212.8] and 27,814.8[4854.5]). Equal amounts of nursing occurred from both left and right mammary glands for the 42‐day time period (means[sd] [seconds] for left and right, respectively; 13,800.4[2,787.0] and 15,328.7[2,471.0]; P = 0.30). Zoo Biol 18:373–384, 1999. © 1999 Wiley‐Liss, Inc.     

Preventing physical interactions between parturient ewes and their neonate differentially impairs the development of maternal responsiveness and selectivity depending on maternal experience

The present study investigated whether deprivation of nursing or of any physical interaction with the lamb impairs the onset of maternal responsiveness and the establishment of selectivity in primiparous and multiparous ewes. Just after parturition, ewes could interact freely with their lamb, or could only lick their lamb but not nurse them, or could neither lick nor nurse them for the first 4 h. At 4 h, mothers were successively observed for 3 min with an alien lamb and then with their own lamb. Only 5/14 primiparous mothers accepted their own lamb following deprivation of all physical contact whereas all multiparous mothers did so (19/19). Also, deprivation of all physical contact resulted in a significantly higher proportion of multiparous mothers accepting an alien lamb (6/18) than following deprivation of nursing only (0/19) indicating an impairment in selectivity. Finally, there was no indication that preventing only nursing led to a deficit either in maternal responsiveness or selectivity, neither in primiparous nor in multiparous ewes. These findings underline the importance of perception of olfactory cues from amniotic fluids through licking and/or physical contact and interacting with the lamb for the development of maternal responsiveness and selectivity.     

Energetics of age-specific reproductive effort in female Harp seals, Phoca groenlandica

The theory of reproductive effort is commonly viewed in the perspective of the cost of offspring to the parent. This interpretation predicts that older females make a greater reproductive effort than younger females, for whom the cost of lost future offspring is less. The benefit early-born offspring represent in future generations is greater than that of late-born offspring in most natural populations, so, alternatively, young females should make a greater reproductive effort. These hypotheses were investigated in nursing Harp seals by examining age-specific reproductive effort in terms of energetic maternal investment.
Younger Harp seal females lost weight at the same rate as did older females. Moreover. since younger, growing females tended to start lactation with less blubber than older females. weight loss during 10 days (d) of lactation represented a greater proportion of stored energy for young females. A successfully weaned pup, therefore, constituted a greater reproductive effort for them than for older females, consistent with benefit–oriented predictions from theory.
A model is presented to outline the components of an annual energy budget for female Harp seals in the context of reproductive effort. This model indicates that young females may devote a greater proportion of their annual net energy to reproduction and take a greater risk of lost future reproduction. It also identifies areas of inadequacy of existing data on pinniped energy budgets.     

Brain serotonin determines maternal behavior and offspring survival

Maternal care is an indispensable component of offspring survival and development in all mammals and necessary for reproductive success. Although brain areas regulating maternal behaviors are innervated by serotonergic afferents, very little is known about the role of this neurotransmitter in these behaviors. To evaluate the contribution of serotonin to maternal care, we used mice with a null mutation in the gene for tryptophan hydroxylase‐2 (TPH2), which results in a genetic depletion of brain serotonin, and tested them in a wide range of maternal behavior paradigms. We found that litters born to and reared by TPH2^?/? mothers showed decreased survival, lower weaning weights and increased cannibalization. In addition, TPH2^?/? mothers performed poorly in pup retrieval, huddling, nest construction and high‐arched back nursing. Aggression in TPH2^?/? dams was not triggered by lactation and was steadily high. Survival and weaning weight deficits of TPH2^?/? pups were rescued by cross‐fostering and in litters of mixed genotype (TPH2^?/? and TPH2^?/+). However, the maternal behaviors of TPH2^?/? dams did not improve when rearing either TPH2^+/+ pups or mixed‐genotype litters. In addition, TPH2^?/? pups significantly worsened the behavior of TPH2^+/+ dams with respect to cannibalism, weaning weight and latency to attack. Olfactory and auditory functions of TPH2^?/? females or anxiety‐like behaviors did not account for these maternal alterations as they were equal to their TPH2^+/+ counterparts. These findings illustrate a profound influence of brain serotonin on virtually all elements of maternal behavior and establish that TPH2^?/? pups can engender maladaptive mothering in dams of both genotypes.     

Energetics of lactation in harp seals (Phoca groenlandica) from the gulf of St. Lawrence,Canada

 This study reports the findings of an integrated, comprehensive analysis of lactation energetics in harp seals conducted using longitudinal measurements of mass, body composition and milk composition from mother-pup pairs in conjunction with water flux measurements in pups. The nursing period of harp seals is a short, intense and relatively efficient period of energy transfer from mothers to pups. The average daily milk intake for pups was 3.65±0.24 kg which is equivalent to 79.5 MJ of energy. Eighty-one per cent of the energy received in the milk was metabolisable and 66% of the energy was stored by the pups as body tissue. The field metabolic rate of pups was 3.9±0.4 time basal metabolic rate. The pups were growing at a rate of 2.2 kg per day during the nursing period. The distribution of this mass gain varied in terms of tissue composition, depending on the age of the pups, but over the whole nursing period approximately half of the tissue was stored as fat. Harp seal mothers lost an average of 3.1 kg per day during lactation which was composed of 37% water, 50% fat, 11% protein and 2% ash. Mothers spent half of their time during the lactation period actively diving and only one-third of their time on the surface of the ice. Milk compositional changes followed the normal phocid pattern with increasing fat content and decreasing water content as lactation progressed. The mean mass transfer efficiency was 73%. However, this value cannot be used without qualification because female harp seals in this study fed to varying degrees, consuming an estimated 0–4.8 kg of fish per day. Feeding does not appear to be required in order to achieve the energy requirements for lactation, given the energy stores possessed by females, and some females do fast through the entire period so feeding may be considered opportunistic in nature. Accepted: 25 April 1996     

Lucerne silage in high yielding dairy cows: effect of parity and analysis of reasons in mixed-parity group housing using random regression test-day models

A study with high-yielding dairy cows was re-analysed in order to test the suitability of lucerne silage separately for primi- and multiparous cows as an alternative to grass silage in maize-based total mixed rations (TMR). Lactation curves were fitted using random regression test-day models for energy corrected milk (ECM) and dry matter intake (DMI) as well as for number and duration of feeder visits (NFV and DFV, respectively). Existing models for ECM and DMI were extended by animal-specific random effects, which were formulated in their dependency on days in milk. For NFV and DFV random regression models were applied for the very first time. The chosen approach of statistical analysis permitted comparisons of the lactation curves as well as of least square means for sub-periods to answer nutritional questions. Whilst primiparous cows had generally lower DMI and ECM as compared to multiparous cows, only in primiparous cows a negative effect of lucerne TMR on ECM was observed, especially in early lactation. Nutritional factors should be rejected because of very similar ECM between the various TMR in multiparous cows. Traits of feeding behaviour indicated that particle size could contribute to the decreased ECM. Even more impact on the lower ECM should be addressed to domination behaviour of multiparous cows. The resulting restlessness of primiparous cows caused a reduced intake per minute spent at the feeder. Further studies should focus on optimising the proportion and chopping length of lucerne in the diet and to improve flock management to maximise feed intake of primiparous cows. Generally, statistical analysis of lactation data became a very complex issue. It seems inevitable that nutritionists and statisticians team up to address this problem.