Pup Mortality Research Articles

Growth and survival of New Zealand sea lions, Phocarctos hookeri: birth to 3 months

Offspring birth mass and growth rate represent important life history traits, which influence many vital population and individual characteristics, while offspring survival is a key factor in variation in female reproductive success. For a threatened population of pinnipeds, such as New Zealand sea lions, Phocarctos hookeri, (Grey, 1844, NZ sea lions), understanding individual life history parameters and population dynamics is vital for their management and conservation. This is the first study of the behaviour of females during parturition, pup birth mass and growth, and pre-weaning survival of NZ sea lions, Enderby Island, Auckland Islands during austral summer breeding seasons, 2001/2002 to 2003/2004. Pregnant females arrived ashore 2.1 ± 0.16 days prior to giving birth. After parturition, mothers suckled their pups for 8.6 ± 0.16 days before leaving on their first foraging trip. Male pups were born significantly heavier than female (males 10.6 ± 1.4 kg, females 9.7 ± 0.9 kg). Pups lost on average 48 ± 0.14 g per day mass during the early postpartum period (between birth and mothers first foraging trip). Pup mortality did not vary by pup sex, birth mass, date of birth or any maternal characteristics however it varied significantly between years due to a bacterial infection epidemic (Pup mortality at 60 days: 2001 32%; 2002 21%; 2003 12%). The absolute growth rate per day for pups was 151 g/day over all years. Pup growth rate measured as the slope of linear line fitted to pup mass by age was consistently higher for pups with heavier birth mass, male pups and during the 2002 season. High offspring mortality and slow growth rates coupled with maternal foraging behaviour at their physiological limits may reflect a threatened species which has limited ability for population growth in an environment which is at the extreme of their historical range and impacted upon by fisheries.

Local over-expression of prolactin in differentiating mouse mammary gland induces functional defects and benign lesions, but no carcinoma

Experimental, clinical, and epidemiological data support the growth-promoting role of endocrine prolactin (PRL) in mammary tumors. PRL is also produced by the breast, where it is now recognized to act as a growth/survival factor via autocrine/paracrine mechanisms. Recent transgenic (Tg) mouse models have revealed the pro-oncogenic effect of PRL over-expression in virgin mammary glands. To address the question whether PRL tumorigenicity was maintained on differentiated mammary glands, we generated mammary-specific Tg mice expressing human (h)PRL under the control of the milk whey acidic protein promoter, which directs autocrine hPRL over-expression in late gestation throughout lactation. Minimal levels of transgene expression were detected in the mammary glands of virgin animals, which at best induced partial ductal branching and lobulo-alveolar structures in older nulliparous females. As expected, expression of mammary hPRL dramatically increased at the end of first pregnancy, and from this point it never returned to baseline, although it peaked at each gestation/lactation cycle. Over-expression of hPRL that starts when the gland is already well into the differentiation process led to various morphological mammary alterations, including abnormally differentiated epithelium, atropy of the myoepithelial layer, dilated ducts, cysts, and lymphocytic infiltrates. These phenotypes tended to worsen with successive pregnancies, also reflecting cumulative damage of failure of involution. Although some older, multiparous females developed benign tumors (papillomas and metaplasias), none of the animals studied developed mammary carcinomas. In addition, we noticed that half of the Tg females exhibited lactation defects, leading to significantly increased pup mortality. This phenotype was due neither to failure of milk production nor to modification of its protein content, but rather it was correlated to lipid enrichment of the milk, which, in combination with profoundly altered morphology of the gland, led to impaired milk extrusion through the nipple. In summary, these data show that over-expression of autocrine hPRL in a differentiating mammary gland induces dramatic functional and morphological defects, but not carcinoma. This deserves further investigations on the emerging concept that autocrine PRL may have different effects on pathological development of the mammary gland depending on the differentiation state of the latter.

Peroxisome Proliferator-Activated Receptor α Activation during Pregnancy Severely Impairs Mammary Lobuloalveolar Development in Mice

To identify the potential functions of peroxisome proliferator-activated receptor alpha (PPARalpha) in skin development, transgenic mice were generated to target constitutively activated PPARalpha (VP16PPARalpha) to the stratified epithelia by use of the keratin K5 promoter. In addition to marked alterations in epidermal development, the transgenic mice had a severe defect in lactation during pregnancy resulting in 100% pup mortality. In this study, the alteration of mammary gland development in these transgenic mice was investigated. The results showed that expression of the VP16PPARalpha transgene during pregnancy resulted in impaired development of lobuloalveoli, which is associated with reduced proliferation and increased apoptosis of mammary epithelia. Mammary epithelia from transgenic mice also showed a significant reduction in the expression of beta-catenin and a down-regulation of one of its target genes, cyclin D1, which is thought to be required for lobuloalveolar development. Furthermore, upon PPARalpha ligand treatment, similar effects on lobuloalveolar development were observed in wild-type mice, but not in PPARalpha-null mice. These findings suggest that PPARalpha activation has a marked influence in mammary lobuloalveolar development.

Protection against congenital cytomegalovirus (CMV) disease, conferred by a replication-disabled, bacterial artificial chromosome (BAC)-based DNA vaccine

It is unclear if protective immunity can be conferred by a cytomegalovirus (CMV) vaccine encoding a single protein subunit, or if multiple viral genes need to be targeted. Using the guinea pig model of congenital CMV infection, these studies examined the immunogenicity and efficacy of a DNA vaccine based on the guinea pig cytomegalovirus (GPCMV) genome cloned as a non-infectious BAC plasmid, modified by transposon insertion into the homolog of the HCMV tegument protein, UL48. Following vaccination of female Hartley guinea pigs with BAC DNA, adverse GPCMV-related pregnancy outcome were assessed after establishment of pregnancy, followed by GPCMV third-trimester challenge. Animals immunized with recombinant BACmid engendered anti-GPCMV antibodies by ELISA assay. Immunogenicity of BAC plasmid DNA was augmented by inclusion of the lipid adjuvant, DOTMA/DOPE, in the vaccine regimen. Among pups born to 12 control (sham-immunized) dams challenged with GPCMV in the third trimester, mortality was 23/35 (66%). In contrast, among evaluable pregnancy outcomes in pups born to 10 BAC-immunized pregnant dams, preconception immunization resulted in reduced pup mortality, to 10/34 pups (29%; p < 0.005 versus control, Fisher's exact test). In addition, vaccinated dams had reduced viral load, compared to controls, as assessed by quantitative, real-time PCR.

Interaction of maternal protein and carbon monoxide on pup mortality in mice: implications for global infant mortality

The United States Surgeon General declared 2005 as the "Year of Healthy Child." To improve the health of all children, we need to start before pregnancy, with their mothers. Unfortunately, protein deficiency in the diets of poor pregnant mothers in developing countries is widespread. Carbon monoxide (CO) pollution is serious public health problem in developed and developing countries. A two-way factorial experimental design was used. Mice were maintained on 27%, 16%, 8%, or 4% protein diets. Dams were exposed to 0 ppm (control), 65 ppm, or 125 ppm CO in air, in environmental chambers for 6 hr/day during the first 2 weeks of pregnancy. Controls were also subjected to environmental chamber conditions. Food and water were available at all times. Animals were allowed to deliver, and data on pup mortality was recorded. Litter size was not affected by CO exposure, but was directly related to the dietary protein levels. Pup weight was inversely related to the CO exposure level, and directly related to the dietary protein levels. Pup mortality on date of birth was increased by CO exposure and was inversely related to the dietary protein levels. Pup mortality at 1 week of age was increased by CO exposure and 55% of all pups died in 125 ppm CO exposed group. Pup mortality at 1 week of age was inversely related to dietary protein levels. All pups in the 4% dietary protein and in all concentrations of CO died. All pups in the 8% protein group and in all CO concentrations died except in 125 ppm CO group. Pup mortality in the 16% dietary protein group ranged from 14.8% in 0 ppm to 36.8% in 65 ppm CO groups. Pup mortality in the 27% dietary protein group ranged from 14.3% in the 0 ppm to 41.1% in the 125 ppm CO groups. DATA suggest that protein deficiency and CO exposure enhance pup mortality. The protein and CO also interact to increase pup mortality in 16% and 27% protein groups. Carbon monoxide exposure, along with protein deficiency during gestation, may be contributing factors for high rates of infant mortality in developing countries. The results of the study also suggest that un-vented combustion for heating and cooking, ambient pollution, and biomass smoke may have a major impact on the health of children worldwide; and may explain the causes of high infant mortality in poor countries and some sections of the United States population.

Contrasting effects of heterozygosity on survival and hookworm resistance in California sea lion pups

Low genetic heterozygosity is associated with loss of fitness in many natural populations. However, it remains unclear whether the mechanism is related to general (i.e. inbreeding) or local effects, in particular from a subset of loci lying close to genes under balancing selection. Here we analyse involving heterozygosity-fitness correlations on neonatal survival of California sea lions and on susceptibility to hookworm (Uncinaria spp.) infection, the single most important cause of pup mortality. We show that regardless of differences in hookworm burden, homozygosity is a key predictor of hookworm-related lesions, with no single locus contributing disproportionately. Conversely, the subsequent occurrence of anaemia due to blood loss in infected pups is overwhelmingly associated with homozygosity at one particular locus, all other loci showing no pattern. Our results suggest contrasting genetic mechanisms underlying two pathologies related to the same pathogen. First, relatively inbred pups are less able to expel hookworms and prevent their attachment to the intestinal mucosa, possibly due to a weakened immune response. In contrast, infected pups that are homozygous for a gene near to microsatellite Hg4.2 are strongly predisposed to anaemia. As yet, this gene is unknown, but could plausibly be involved in the blood-coagulation cascade. Taken together, these results suggest that pathogenic burden alone may not be the main factor regulating pathogen-related mortality in natural populations. Our study could have important implications for the conservation of small, isolated or threatened populations, particularly when they are at a risk of facing pathogenic challenges.

Effects of Maternal Campylobacter rectus Infection on Murine Placenta, Fetal and Neonatal Survival, and Brain Development.

Maternal periodontal infection has been associated with increased risk of prematurity and low birthweight. Infection and inflammatory pathways that mediate prematurity have also been implicated in neonatal developmental impairments. The objective of this study was to determine whether maternal Campylobacter rectus infection that induces fetal growth restriction in a mouse model also compromises neonatal pup survival, growth, and neurodevelopment. Timed pregnant mice were challenged with C. rectus on gestation day 7.5. One group of animals was sacrificed on embryonic day 16.5 for placental histology and measurement of fetal brain mRNA expression of tumor necrosis factor (TNF)-α and interferon (IFN)-γ. Another group of animals was allowed to deliver to follow pup survival, growth, and brain structure at day 9. C. rectus challenge resulted in abnormal placental architecture with inflammation and a 2.8-fold increase in fetal brain expression of IFN-γ (P = 0.04). Pup birthweight was unaffected by C. rectus exposure, but lethality was 3.9-fold higher after 1 week. Ultrastructurally, the 9-day neonatal brain tissue displayed cellular and myelin alterations consistent with white matter damage. Maternal C. rectus infection induces placental inflammation and decidual hyperplasia as well as concomitant increase in fetal brain IFN-γ. Maternal infection increased pup mortality, and preliminary findings demonstrate ultrastructural changes in the hippocampal region of the neonatal brain, in a manner analogous to the effects of maternal infection on white matter damage seen in humans. Thus, the threat of maternal oral infectious exposure during pregnancy may not be limited to the duration of gestation, but may also potentially affect perinatal neurological growth and development.

Two-generation reproduction and cross-foster studies of perfluorooctanesulfonate (PFOS) in rats

Perfluorooctanesulfonate (PFOS) is a persistent acid found widely distributed in wildlife and humans. To understand the potential reproductive and developmental effects of PFOS, a two-generation reproduction study was conducted in rats. Male and female rats were dosed via oral gavage at dose levels of 0, 0.1, 0.4, 1.6, and 3.2 mg/(kg day) for 6 weeks prior to mating, during mating, and, for females, through gestation and lactation, across two generations. Due to substantial F 1 neonatal toxicity observed in the 1.6 and 3.2 mg/(kg day) groups, continuation into the second generation was limited to F 1 pups from the 0, 0.1, and 0.4 mg/(kg day) groups. No adverse effects were observed in F 0 females or their fetuses upon caesarean sectioning at gestation day 10. Statistically significant reductions in body-weight gain and feed consumption were observed in F 0 generation males and females at dose levels of 0.4 mg/(kg day) and higher, but not in F 1 adults. PFOS did not affect reproductive performance (mating, estrous cycling, and fertility); however, reproductive outcome, as demonstrated by decreased length of gestation, number of implantation sites, and increased numbers of dams with stillborn pups or with all pups dying on lactation days 1–4, was affected at 3.2 mg/(kg day) in F 0 dams. These effects were not observed in F 1 dams at the highest dose tested, 0.4 mg/(kg day). Neonatal toxicity in F 1 pups, as demonstrated by reduced survival and body-weight gain through the end of lactation, occurred at a maternal dose of 1.6 mg/(kg day) and higher while not at dose levels of 0.1 or 0.4 mg/(kg day) or in F 2 pups at the 0.1 or 0.4 mg/(kg day) dose levels tested. In addition to these adverse effects, slight yet statistically significant developmental delays occurred at 0.4 (eye opening) and 1.6 mg/(kg day) (eye opening, air righting, surface righting, and pinna unfolding) in F 1 pups. Based on these data, the NOAELs were as follows: reproductive function: F 0 ≥ 3.2 and F 1 ≥ 0.4 mg/(kg day); reproductive outcome: F 0 = 1.6 and F 1 ≥ 0.4 mg/(kg day); overall parental effects: F 0 = 0.1 and F 1 ≥ 0.4 mg/(kg day); offspring effects: F 0 = 0.4 and F 1 ≥ 0.4 mg/(kg day). To distinguish between maternal and pup influences contributing to the perinatal mortality observed in the two-generation study, a follow-up cross-foster study was performed. Results of this study indicated that in utero exposure to PFOS causally contributed to post-natal pup mortality, and that pre-natal and post-natal exposure to PFOS was additive with respect to the toxic effects observed in pups.

Use of benchmark dose and meta-analysis to determine the most sensitive endpoint for risk assessment for dimethoate

A meta-analysis of several rat toxicity studies for dimethoate was conducted to determine the most sensitive endpoint for use in risk assessment. The analysis was motivated by a recent developmental neurotoxicity (DNT) study, which identified the same no observed adverse effect level (NOAEL) for pup mortality and cholinesterase inhibition. The pup mortality NOAEL was lower than that determined in a range-finding study for the DNT and other reproduction studies, and was highly influenced by a single total litter loss in the middle dose group, which made interpretation difficult. First, a meta-analysis was conducted of four recent studies by gavage dosing with very similar designs, including the DNT. Benchmark dose (BMD) modeling was used to determine the appropriate point of departure for regulatory purposes, the lower limit of the BMD for a 5% incidence for pup mortality (BMDL 5) and the lower limit of a 10% inhibition of brain cholinesterase ( BMDL 10 ∗ ) , the asterisk denotes that the BMD is based on continuous response variable as opposed to an incidence level. For pup mortality, the BMDL 5 for post-natal days (PND) 1–4 was 0.64 mg/kg/day. For cholinesterase inhibition, the lowest BMDL 10 ∗ was 0.19 mg/kg/day for the dams at gestation day 20. These results show that the regulatory point-of-departure for cholinesterase inhibition is more than threefold lower than pup mortality. Thus, risk assessments protecting against cholinesterase inhibition are likely to also be protective of pup mortality. In addition, cholinesterase inhibition and pup mortality were evaluated in two 2-generation reproduction studies by dietary exposure. Also, cholinesterase inhibition was evaluated in a 28-day dietary study. Dietary exposure is more relevant than gavage exposures for many human risk assessment scenarios. There was no consistent pup mortality at the highest doses of the two 2-generation dietary studies (6.0 and 6.5 mg/kg/day). The average BMD 10s for brain cholinesterase inhibition for the 2-generation studies was 0.65 mg/kg/day, with a range of 0.49–0.96 mg/kg/day. This suggests that cholinesterase inhibition is at least a 10-fold more sensitive endpoint than pup mortality for dietary exposures. For the 28-day dietary study, the BMD 10 for brain cholinesterase inhibition was 1.1 mg/kg/day for males and 0.70 mg/kg/day for females. The exposure duration in the 28-day dietary study is closest to the durations in the gavage studies. Compared to the dams in the gavage studies, which had a BMDL 10 of 0.19 mg/kg/day, the animals were more than threefold more sensitive to cholinesterase inhibition by gavage compared to dietary exposure.

Critical window of male reproductive tract development in rats following gestational exposure to di‐n‐butyl phthalate

Gestational exposure to di-n-butyl phthalate (DBP), a ubiquitous environmental contaminant, has been shown to interfere with the development of the male reproductive tract by acting as an antiandrogen. This study was conducted to identify the critical days for the abnormal development of the male reproductive tract, specifically the testis and epididymis. Timed-pregnant Sprague-Dawley rats were dosed with DBP at 500 mg/kg/day on gestation day (GD) 14 and 15, 15 and 16, 16 and 17, 17 and 18, 18 and 19, or 19 and 20 (GD 0=plug day). Anogenital distance (AGD) was measured on postnatal day (PND) 1 and 13, while areloa number was recorded on PND 13 only. After weaning, males were allowed to mature to PND 90 at which time they were necropsied. Areloa number and AGD were recorded and testes, epididymides, seminal vesicles, prostate gland, kidneys, and liver weighed. Blood serum was collected and assayed for total testosterone concentration. There were no observable effects on litter size, sex ratio, serum testosterone concentration, or mortality of pups. Statistically significant permanent reductions in AGD were seen in males exposed prenatally to DBP on GD 15 and 16 or GD 18 and 19. On PND 13, areola were present in males exposed to DBP on GD 15 and 16, 16 and 17, 17 and 18, and 19 and 20. However, permanent retention occurred only in males after DBP exposure on GD 16 and 17. Exposure to DBP on only GD 17 and 18 elicited a reduction in epididymal weights; while exposure on only GD 16 and 17 caused a significant increase in the weights of the testes due to edema. In this study, epididymal and testicular malformations were most prevalent after exposure to DBP on any gestational day. Epididymal malformations, characterized by agenesis of various regions and small or flaccid testes were significantly increased in DBP-exposed males only on GD 16 and 17. These findings suggest that 2-day DBP exposure is highly detrimental to the developing reproductive tract of the male fetus and the critical window for abnormal development is GD 16-18.

Postnatal development of rat pups after maternal exposure to diethanolamine

Diethanolamine (DEA), a widely used surfactant, was administered to pregnant mice at the oral LD10 resulting in failure of pups to grow and thrive through postnatal day (PND) 3 [National Toxicology Program, 1987; York et al., Teratology 37:503-504, 1988]. The toxicity profile for DEA differs among rodent species. This study investigated DEA-induced postnatal toxicity in a second species. Timed-mated Sprague-Dawley rats were dosed (0, 50, 125, 200, 250, or 300 mg DEA/kg/day, p.o.) on gestational days (GD) 6-19. Dams and pups were monitored for body weight, feed/water intake, clinical signs, litter size, and sex ratio. At necropsy (PND 21), maternal liver and kidney weights and number of uterine implantation sites were recorded. The high-dose group was terminated early due to excessive toxicity. The estimated maternal LD10 was 218 mg/kg/day. Maternal effects included decreased body weight and relative feed intake (>or=200 mg/kg/day), transiently reduced relative water intake (125 and 250 mg/kg/day), and increased absolute kidney weight (>or=125 mg/kg/day). Postimplantation loss (PND 0) and pup mortality (PND 0-4) were increased (>or=200 and >or=125 mg/kg/day, respectively). Pup body weight was reduced (>or=200 mg/kg/day) as late as PND 21. This study demonstrates reduced postnatal growth and survival in a second species after gestational exposure to DEA, persistence of toxic effects through the end of lactation, possibly due to long elimination half-life, and maternal and developmental toxicity no-observed-adverse-effect level (NOAELs) (50 mg/kg/day) and lowest-observed-adverse-effect level (LOAELs) (125 mg/kg/day) for oral DEA exposure during embryo/fetal development in the rat.

Distribution, abundance and growth of New Zealand sea lion Phocarctos hookeri pups on Campbell Island

Nine weeks field work was completed during two trips in January/February and March/ April 2003 to investigate the distribution and abundance of New Zealand sea lion Phocarctos hookeri pups at Campbell Island. A total of 161 pups were tagged and a further 138 dead pups were found. A closed mark‐recapture model was used to estimate the total number of live pups (e.g., tagged plus untagged pups) at Campbell Island in April as 247 (SE = 28, 95% CI 198–308). Pup production at Campbell Island is estimated at 385, which comprises 13% of the total pup production for the species in the 2003 season. This is the first robust estimate of pup production for New Zealand sea lions at Campbell Island. The figure of 385 pups is considerably higher than any of the previous estimates reported from Campbell Island. The high level of pup mortality (36%) at Campbell Island for approximately the first 2 months after birth is higher than the 17% reported for the Auckland Islands for approximately the same period in 2003, but is similar to unusually high levels of mortality (20–30%) reported at the Auckland Islands in recent years. It was not possible to determine the cause of death of the 138 dead pups owing to scavenging and decomposition. Pups were found over the whole Island, with the exception of its northern end. Male pups were significantly heavier and faster growing than female pups over the same period.

The use of a cat-flap at the nest entrance to mimic natural conditions in the breeding of fattening rabbits (Oryctolagus cuniculus)

AbstractManagement systems allowing free nest access are widely used in commercial rabbit breeding, but these produce a potential conflict with the doe's behavioural goal of a closed nest entrance. Furthermore, the restricted space in commercial breeding units prevents the doe from achieving a sufficient distance between her and the nest, another highly adaptive behavioural goal. This can lead to behavioural problems and pup mortality higher than 20%, attributable to hypothermia, injuries, weakness caused by the scattering and crushing of pups, or even cannibalism. In this study we tested a type of nest entrance (a metal cat-flap) that visually closed the nest box while still allowing the doe free access during the first 15 days after parturition. The effects of a cat-flap access (group CF) and of a permanently open nest box (group O) on nest-related behaviour, general activity, and plasma corticosterone concentration of the does, and on the mortality and weight of the pups, were compared using 15 ZIKA does in each group. Over 24 h, there was no difference between the groups in the frequency of ‘nest controls’ (approaches or entries to the nest without nursing of pups). However, outside nursing hours, does in group O showed more ‘head contacts’ with the nest, whereas does in group CF performed more nose contacts and nesting activities outside the nest. Does in group O performed twice as many potentially disturbing nest contacts in this time than does in group CF and had a higher increase of corticosterone after the administration of exogenous adrenocorticotrophic hormone. Pup mortality from days 16 to 35 was significantly higher in group O, and pups born to does in group O left the nest earlier. There was no significant difference in the weaning weights of pups between the two groups. As does with a cat-flap at the nest entrance still showed repeated nest approaches, the cat-flap possibly did not block all nest stimuli from the does. Alternatively, it is possible that the repeated approaches to the next box result from its being one of very few attractive or interesting features in an otherwise barren environment. Removal of the nest box from the cage is an effective method to eliminate nest stimuli, but this increases work for the staff without improving the barren environment for the rabbits. A better way of increasing the distance between the doe and the nest, as well as presenting a number of other attractive features, is group-housing of does.

Causes of offspring mortality in the Antarctic fur seal, Arctocephalus gazella: the interaction of density dependence and ecosystem variability

Rates of pup production and causes of pup mortality, recorded in a designated study colony on Bird Island, South Georgia, from 1989 to 2003, were used to evaluate the factors influencing the growth of the population of Antarctic fur seals, Arctocephalus gazella (Peters, 1875). The mean number of pups produced per year was 680 (range 444–822) with a mean survival rate of 77.6% (range 52.6%–92.8%). Starvation, arising from reduced food availability within the mothers' foraging area, was the most frequently recorded cause of death and was positively correlated with the overall rate of pup survival, although it showed no relationship with the number of pups produced. However, traumatic injury showed a local relationship with seal density, increasing significantly with increasing numbers of seals born. This suggests that environmental processes that reduce the availability of prey to lactating mothers, rather than space limitation within colonies, are the limiting factor in the population increase of Antarctic fur seals at South Georgia. The spatial scales over which such processes operate, relative to the local-scale effects of densities of animals within colonies, have important implications for the future expansion of the population and the resultant trophodynamic interactions.

Antihypertensive effects of flutamide in rats that are exposed to a low-protein diet in utero

We investigated whether gestational age of in utero low-protein diet played a role in the subsequent development of adult hypertension and whether it is gender dependent and examined whether flutamide (a specific, nonsteroidal competitive antagonist of the androgen receptor) reduces blood pressure in rat offspring that are exposed to in utero low-protein diet (6%). Pregnant rats were fed either with 20% protein (control) or 6% protein (low-protein diet) from day 1 or day 12 of gestation. Fetoplacental weights and mortality rates of pups were assessed. Systolic blood pressure, mean arterial blood pressure, and circulatory hormone levels in offspring were determined. In addition, male and female hypertensive offspring were treated with flutamide, and their blood pressure was monitored. After delivery, pup weights were reduced, and pup mortality rates increased in the low-protein diet-day 1 group. Systolic blood pressure and mean arterial blood pressure were elevated in low-protein diet-day 1 males and females and low-protein diet-day 2 males. Significant (P < .05) reduction in blood pressure was achieved with flutamide in low-protein diet-day 1 females. Serum estradiol levels were decreased (P < .05) in low-protein diet-day 1 females; flutamide attenuated this effect. The day of in utero insult by low-protein diet is critical in the induction of adult hypertension; the severity is gender dependent. Flutamide was found to protect against hypertension only in females.

Delayed Motherhood Decreases Life Expectancy of Mouse Offspring1

This study analyzes the long-term effects of delayed motherhood on reproductive fitness and life expectancy of offspring in the mouse. Hybrid (C57BL/6JIco x CBA/JIco) first-generation (F1) females, either at the age of 10 or 51 wk, were individually housed with a randomly selected 12- to 14-wk-old hybrid male following a breeding pen system until females reached the end of their reproductive life. Reproductive fitness of second-generation (F2) females was tested from the age of 25 wk until the end of their reproductive life. In F2 males, the testing period ranged from the age of 52 wk until their natural death. Delayed motherhood of hybrid F1 female mice was associated with a decreased percentage of male F3 offspring at birth and lower life expectancy and body weight during adulthood of F2 offspring. There was, however, no evident negative effect of delayed motherhood on several reproductive fitness variables in either male or female F2 offspring. This included between-parturition interval, litter size at birth and at weaning, body weight at weaning and preweaning mortality of F3 pups, percentage of F3 litters with at least one pup cannibalized, and time at which female and male F2 offspring ceased their reproductive life. These data clearly show that delayed motherhood in the mouse is associated with negative long-term effects on offspring survival.

The influence of pup odour on the nest related behaviour of rabbit does ( Oryctolagus cuniculus)

Under natural and near-to-nature conditions, rabbit does block the entrance to their nest after nursing by burrowing before they leave. This behavioural pattern serves to protect the pups from predators and is a highly evolutionary adaptive behaviours. Under commercial husbandry conditions, the entrance to the nest box stays permanently open, potentially counteracting a doe's behavioural goal of a closed nest. Due to the non-manipulable floor and the absence of roughage or other appropriate materials, a doe will fail to achieve the feedback of a successful removal of nest stimuli, in spite of conducting the appropriate behavioural patterns. This leads to repeated nest contacts, nest visits and nest closing attempts and can increase pup mortality due to the crushing of pups and the disturbance of their energy-saving strategy of resting deep inside the insulating nest material between nursing visits. Previous studies have shown that repeated nest related behaviour is even performed when the nest entrance is closed with a sliding door and opened once a day for nursing. This may be due to the ventilation openings in the nest box, potentially emitting olfactory and acoustic stimuli. To investigate the effects of the olfactory stimulus alone, we provided the cages of 15 ZIKA does with nest boxes which contained no pups and emitted no pup odours (‘N’), and compared the does’ nest related behaviour and general activity when nest boxes were attached which also contained no pups, but potentially emitted pup odour (‘O’). Thus, each doe was both a test and control animal. In both treatments the nest entrance was closed with a sliding door and nursing allowed once a day. The frequency and duration of nest contacts were significantly higher in ‘O’ than in ‘N’. Furthermore, significantly more nesting activities were performed after and outside nursing in ‘O’. Accordingly, the number of hours without nest contacts and nesting activities was significantly lower when a nest box emitting pup odour was attached to the cage. Also, the does’ general activity tended to be higher in ‘O’.

Diet-induced obesity impairs mammary development and lactogenesis in murine mammary gland

We have developed a mouse model of diet-induced obesity that shows numerous abnormalities relating to mammary gland function. Animals ate approximately 40% more calories when offered a high-fat diet and gained weight at three times the rate of controls. They exhibited reduced conception rates, increased peripartum pup mortality, and impaired lactogenesis. The impairment of lactogenesis involved lipid accumulation in the secretory epithelial cells indicative of an absence of copius milk secretion. Expression of mRNAs for beta-casein, whey acid protein, and alpha-lactalbumin were all decreased immediately postpartum but recovered as lactation was established over 2-3 days. Expression of acetyl-CoA carboxylase (ACC)-alpha mRNA was also decreased at parturition as was the total enzyme activity, although there was a compensatory increase in the proportion in the active state. By day 10 of lactation, the proportion of ACC in the active state was also decreased in obese animals, indicative of suppression of de novo fatty acid synthesis resulting from the supply of preformed fatty acids in the diet. Although obese animals consumed more calories in the nonpregnant and early pregnant states, they showed a marked depression in fat intake around day 9 of pregnancy before food intake recovered in later pregnancy. Food intake increased dramatically in both lean and obese animals during lactation although total calories consumed were identical in both groups. Thus, despite access to high-energy diets, the obese animals mobilized even more adipose tissue during lactation than their lean counterparts. Obese animals also exhibited marked abnormalities in alveolar development of the mammary gland, which may partially explain the delay in differentiation evident during lactogenesis.

Morbillivirus neutralising antibodies in Scottish grey seals Halichoerus grypus: assessing the effects of the 1988 and 2002 PDV epizootics

Phocine distemper virus (PDV) may have killed a small number of grey seals Hali- choerus grypus in European waters in 2002, as it was thought to have done in 1988. PDV is known to affect harbour seal population and distribution patterns, but grey seal pup production trends did not correlate consistently with PDV outbreaks. Numbers of known mothers missing from study colonies do not increase in PDV years and pre-weaning pup mortality is similar to that in other years. Pup growth rates are similar in PDV and non-PDV years. Therefore, no direct evidence links PDV out- breaks to changes in grey seal reproductive parameters at the population, colony, or individual level. Investigation of exposure of grey seals to PDV used CDV virus-neutralisation tests on sera collected from breeding seals pre-1988, 1988, 2001 and 2002. No positive sera (≥titre 1:64) were detected prior to 1988. In 1988, 2001 and 2002 the prevalence was 96, 59 and 83%, respectively. In 2001, prevalence in 'old' mothers (of breeding age by 1988, ≥13 yr old) was 63% compared to 0% in 'young' mothers (born after 1989, <13 yr old). In 2002, prevalence was 88 and 93% in old and young mothers, respec- tively. Many pups were seropositive by the end of lactation (North Rona = 36%, Isle of May = 54%). Mean log10 antibody titres increased during lactation and were correlated with the mothers' titre. The high prevalence of seropositives in both adult age groups from geographically separated colonies suggests widespread exposure to a morbillivirus after 2001. This implies that PDV is highly infective and that contact was widespread before the 2002 breeding season.

Exposure to PCB 77 affects the maternal behavior of rats

Polychlorinated biphenyls are environmental contaminants known to affect neurobehavioral development in many laboratory studies using different animal models. Because of their bioaccumulation and long half-life they are a serious concern for our own species. The dioxin-like PCB congener 3,4,3′,4′-tetrachlorobiphenyl (PCB 77) has estrogenic and anti-estrogenic properties, and has been shown to affect brain chemistry and behavior of developing rats when administered during gestation. Since many developmental outcomes in mammals depend upon the type of maternal care provided by the dams, we investigated the effects of two doses of PCB 77 (2 and 4 mg/kg administered during gestational days 6–18) on the maternal behavior of the treated dams. Both doses of PCB 77 reduced the amount of nursing time in which the dams displayed the high-crouch posture over postnatal days 1–6. In addition, the high dose increased the amount of maternal licking and grooming of the litters and the amount of time the dams spent on the nest. The high dose also increased pup mortality, and both doses reduced the weight gain of the litters during the first 6 days of life. These results document effects of PCB 77 on maternal behavior and serve to raise questions about the importance of maternal contributions to the developmental effects of this and similar contaminants.