Competition for Milk in the Domestic Rabbit: Survivors Benefit from Littermate Deaths

We sought evidence for postnatal resource limitation among littermates of the domestic rabbit Oryctolagus cuniculus , and asked whether deaths of indi~vidual pups benefit survivors by increasing their share of milk. Milk ingestion, growth and mortality of 10 chinchilla-breed captive litters were recorded between birth and age 21 d. That milk limits growth and survival was indicated by larger litters showing lower weight gain and higher mortality, and by a significant positive correlation between milk ingested by individual pups and weight increase. Within litters, pups with higher birth weights grew faster, and weight hierarchies became increasingly stable over the 3 weeks, suggesting that advantages accrued during gestation were progressively consolidated during lactation. After individual pups died, the total daily milk weight obtained by the litter was generally unaffected but per capita milk consumption and growth of surviving pups increased, and increases in per capita consumption were greater in smaller litters. The most successful competitors for milk apparently benefit from the deaths of their littermates by obtaining an increased share of an undiminished daily food supply. This relationship has not previously been demonstrated in any vertebrate.     

Prenatal window of susceptibility to perfluorooctane sulfonate-induced neonatal mortality in the Sprague-Dawley rat

The critical period for increased neonatal mortality induced by perfluorooctane sulfonate (PFOS) exposure was evaluated in the rat. Timed-pregnant Sprague-Dawley rats were treated by oral gavage with 25 mg/kg/d PFOS/K(+) on four consecutive days (gestation days (GD) 2-5, 6-9, 10-13, 14-17, or 17-20) or with 0, 25, or 50 mg/kg/d PFOS/K(+) on GD 19-20. Controls received vehicle (10 ml/kg 0.5% Tween-20) on these days. Maternal weight gain was reduced in treated animals during dosing, as were food and water consumption. Following a 4-day treatment, litter size at birth was unaffected while pup weight was similarly reduced in the three earliest PFOS groups. All PFOS groups experienced decreases in survival while controls remained near 100%. Neonatal survival decreased in groups dosed later during gestation, approaching 100% with dosing on GD 17-20. Most deaths occurred before postnatal day (PND) 4, with the majority in the first 24 hours. Maternal serum PFOS levels on GD 21 were higher in groups exhibiting higher mortality. Following a 2-day treatment, PFOS groups experienced significant pup mortality by PND 1. Neonatal mortality continued through PND 5, when survival was 98, 66, and 3% for the 0, 25, and 50 mg/kg groups, respectively. Pup weight was reduced in treated groups with surviving litters. Gross dissection and histological examination of lungs revealed differences in maturation between control and treated animals on PND 0. We conclude that exposure to PFOS late in gestation is sufficient to induce 100% pup mortality and that inhibition of lung maturation may be involved.     

Chronic maternal dietary iodine deficiency but not thiocyanate feeding affects maternal reproduction and postnatal performance of the rat

Iodine deficiency disorders affect reproductive performance in the afflicted populations. Environmental iodine deficiency (ID) and goitrogens are important in their aetiology. We observed earlier that chronic maternal dietary ID but not goitrogen feeding altered the blood-brain barrier nutrient transport in adult rats. Whether similar differences exist in their effects on reproduction of dams and postnatal performance of the offspring has been assessed. Inbred, female, weaning WNIN rats were rendered hypothyroid by feeding for 8-12 weeks, a low iodine test diet or a control diet with added potassium thiocyanate (KSCN) (@ 25 mg/rat/day). Following mating with control males, they continued on their respective diets till their pups were weaned. Indices of reproductive performance such as percentage of conception, mortality of dams during pregnancy and parturition, litter size, and survival of pups till weaning were affected markedly by ID but not thiocyanate feeding. Neither ID nor thiocyanate feeding from conception or parturition affected their reproductive performance. Nevertheless, postnatal weight gain of pups was less in all the three ID groups but not thiocyanate fed dams. Rehabilitation of chronically ID pregnant dams from conception or parturition did not improve their pregnancy weight gain, litter size or birth weight of pups but decreased abortion and mortality of mothers during pregnancy and parturition. Rehabilitation improved the pups' postnatal weight gain but the effect was only moderate. Based on the results of the present study it may be suggested that maternal ID but not thiocyanate feeding affects reproductive performance and postnatal performance of their offspring.     

Development of mouse testis and epididymis following intrauterine exposure to a static magnetic field

In order to test if the in utero exposure to static magnetic fields affects testis and epididymis development in mice, females were exposed to 0.5-0.7 T, generated by a permanent magnet, from day 7 of gestation to the day of birth. No significant differences were found between exposed and sham-exposed animals with respect to body weight gain of dam during the gestational period, litter size, body weight of male pups at the day of birth, and body or testis-epididymis weight gain of pups from birth to day 35. Histopathologic evaluation of testis and epididymis of pups of 1, 5, 15, and 35 days of age showed no detectable alterations due to in utero exposure to static magnetic fields.     

Ventilation in newborn rats after gestation at simulated high altitude

Pregnant rats were kept at a simulated altitude of 4,500 m (PO2 91 Torr) for the whole of gestation and returned to sea level 1 day after giving birth. During pregnancy, body weight gain and food intake were approximately 30% less than in controls at sea level. Measurements were made on the 1-day-old (HYPO) pups after a few hours at sea level. In normoxia, ventilation (VE) measured by flow plethysmography was more (+17%) and O2 consumption (VO2) measured by a manometric method was less (-19%) than in control (CONT) pups; in HYPO pups VE/VO2 was 44% greater than in CONT pups. In acute hyperoxia, VE/VO2 of HYPO and CONT pups decreased by a similar amount (15-20%), indicating some limitation in O2 availability for both groups of pups in normoxia. However, VE/VO2 of HYPO pups, even in hyperoxia, remained above (+34%) that of CONT pups. HYPO pups weighed slightly less than CONT pups, their lungs were hypoplastic, and their hearts were a larger fraction of body weight. An additional group of female rats was acclimatized (8 days) to high altitude before insemination. During pregnancy, body weight gain and food intake of these females were similar to those of pregnant rats at sea level. Measurements on the 1-day-old pups of this group were similar to those of HYPO pups. We conclude that newborn rats born after hypoxic gestation present metabolic adaptation (low VO2) and acclimatization (high VE/VO2), possibly because of hypoxemia. Maternal acclimatization before insemination substantially alters maternal growth in hypoxia but does not affect neonatal outcome.     

Developmental alternations in offspring of female rats orally intoxicated by aluminum chloride or lactate during gestation

The oral treatment of pregnant rats by aluminum chloride or lactate at various doses was applied from day 1 to day 21 of gestation to determine its influence on mortality, weight evolution, and neuromotor maturation of their pups. No effect of treatment on litter size was detected, but an increased mortality appeared during the first week: treatment by aluminum lactate was less active than was an equivalent treatment by aluminum chloride. Weight was transitorily delayed, but the reversal of this effect could be attributed to the decrease of litter size. The neuromotor maturation of surviving pups treated with the two aluminum salts showed an important impairment during the first 2 weeks of postnatal life.     

Effect of short-term hypothyroidism on reproduction in the bitch

Hypothyroidism in bitches has been reported to cause a variable interestrus interval, infertility, abortion, and stillbirth. The objective of this study was to evaluate the effect of experimentally induced hypothyroidism in bitches on fertility, pregnancy, parturition, and neonatal health. Eighteen healthy multiparous bitches were used; hypothyroidism was induced (by radioiodine administration) in nine bitches and the remaining nine served as untreated controls. After breeding, bitches were evaluated for pregnancy, fetal resorption, gestation length, litter size, duration and strength of uterine contractions (during parturition), interval between delivery of pups, viability of pups at birth, periparturient survival, and weight of pups at birth through 4 weeks of age. Bitches were bred a median of 19 weeks after induction of hypothyroidism. All bitches became pregnant and delivered term litters. There was no difference in the interestrus interval, litter size, or gestation length between hypothyroid and control bitches. Duration of uterine contractions was longer, but contraction strength was weaker in hypothyroid than control bitches; however, the interval between delivery of pups was not affected. Periparturient puppy mortality was significantly higher in litters from hypothyroid bitches. Viability scores and weight at birth were significantly lower in pups from hypothyroid bitches than controls. There was no difference between groups in pup weight gain during the first 4 weeks, in the interval from birth to the eyes opened, or to the onset of walking. Although hypothyroidism of relatively short duration did not affect fertility, it prolonged parturition and reduced pup survival in the periparturient period.     

Comparative effect of Neospora caninum infection in BALB/c mice at three different gestation periods

Neospora caninum has been recognized as a major cause of infectious bovine abortion worldwide. In the present study, the effect of N. caninum infection in mice at the 3 gestation periods (first, second, and third period) was investigated. In dams, tissue distribution of N. caninum was evaluated by nested polymerase chain reaction. In the progeny, fetal mortality, stillbirth, litter size, neonatal mortality/morbidity, vertical transmission, and parasite burden in neonatal tissues were evaluated. Pregnant BALB/c mice were infected subcutaneously with 2 x 10(6) NC-1 tachyzoites on days 0, 7, or 14 of gestation. Dams from each group were sequentially killed during gestation and postpartum (PP). Pups were killed on days 1 and 7 PP. Infection on day 0 of gestation produced a high vertical transmission rate, although no changes in fetal mortality, stillbirth, and littermate size were observed. The highest level of vertical transmission, together with an increase in fetal mortality and stillbirth and a decrease in litter size, were observed when infection was done on day 7 of gestation. Finally, infection on day 14 of gestation produced the lowest vertical transmission. Furthermore, infection at any time during gestation compromised the postnatal development of pups, because neonates from infected dams showed less body weight and a delay in the hair development.     

Maternal behavior after the administration of morphine or naloxone to pregnant female rats and the pain sensitivity and brain mu-opioid receptors in the progeny]

Morphine or naloxone injected twice a day (10 mg/kg/day) to rat females from 15 to 18 days of gestation had no effect on their litter size or body weight of pups. Time necessary for the female to bring pups into the nest from the opposite end of the cage, that is a characteristic of maternal care and negatively correlated with the mean body weight of the pup in the litter, did not change after treatment with drugs during gestation. Newborns treated with mu-opioid receptor ligands during intrauterine development had an elevated number of 3H-naloxone binding sites in the brain. However, the number of 3H-naloxone binding sites on the 9 and 16 days of life, as well as pain thresholds under electric stimulation of the tail at a month age were equal in these rats and offsprings of the intact or saline treated mothers.     

Effects of cobalt on postnatal development and late gestation in rats upon oral administration

Four groups of pregnant Wistar rats, each of which consisted of 15 animals were administered 0, 12, 14 and 48 mg/kg/day of cobalt (II) chloride from the 14th day of gestation through 21 days of lactation. The offspring were observed for mortality, body weight, body and tail length and general symptomatology after 1, 4 and 21 days of nursing. The number of litters was higher for the control group. The survival ratios were also higher for the control group. Besides, a dose-dependent delay in the growth of the living young could be observed. No significant differences in organ weights in the animals killed 21 days after birth were observed. The blood parameters analysed did not show differences between the treated and control pups. Cobalt produced toxic effects on the mothers, affecting the late gestation as well as the postnatal development of the pups.     

Effects of maternal ethanol consumption during pregnancy or lactation on intestinal absorption of folic acid in suckling rats

A fostering/crossfostering analysis of the effects of maternal ethanol exposure on jejunal and ileal folate absorption was performed. Male and female rats were randomized into two groups. In the first group, ethanol-treated rats received ad libitum 5, 10 and 15% ethanol in the drinking fluid during three successive weeks. A consumption of 20% was maintained in this group for 5 additional weeks. Ethanol-treated rats were mated. Group 2 served as the control. To study the effect of chronic alcoholism during lactation or gestation separately, at birth (2nd day postpartum) control newborns were cross-fostered to ethanol dams (EG), and the pups issued from the ethanol treated mothers were cross-fostered to control dams (CG). Thus, three experimental groups of pups were formed: (1) control pups receiving no treatment during gestation and lactation (CG); (2) pups exposed to ethanol only during gestation (GG); and (3) pups exposed to ethanol only during lactation (LG). At 21 days postpartum the jejunal and distal ileum folate absorption was determined in the offspring rats by a perfusion technique. Milk folic acid levels were determined by an immunoluminometric assay. The results showed an increase in jejunal folic acid absorption in offsprings exposed to ethanol only during the lactation period (LG). However, in pups exposed to ethanol only during the gestation period (GG), the jejunal folic acid absorption was significantly increased only at concentrations of 0.25, 0.5 and 2.5 microM. No free folic acid absorption occurred in the distal ileum of control pups (CG) at day 21 at all assayed concentrations but in offsprings exposed to ethanol only during the gestation or lactation periods absorption did take place. Pups exposed to ethanol during the gestation period (GG) showed decreased values in ileum folic acid absorption at the lowest assayed concentration (0.25 microM) compared to values obtained for pups exposed to ethanol only during lactation (LG). Milk folic acid levels were significantly decreased in the ethanol-fed dams on day 21 of lactation. These results indicate that exposure of rats to ethanol during the lactation period affects more severely postnatal development of intestinal functions than ethanol exposure only during gestation. In summary, both the exposure to ethanol itself and the decrease in folic acid intake caused alterations in the function of the intestinal mucosa in the offspring, which in turn altered absorption time and development. However, the present results do not explain how ethanol stimulated intestinal absorption of folic acid in pups exposed to ethanol during the gestation or lactation periods. Further studies are needed.     

The effect of diet and feeding level on survival and weight gain of hand-raised harbor seal pups (Phoca vitulina)

Hundreds of stranded harbor seals pups (Phoca vitulina) are brought to wildlife rescue centers every year. Typical hand-rearing diets include artificial milk-replacers and diets based on macerated fish fed via gavage, but weight gains are often low and mortality rates can be high. This study compared survival and weight gain of orphaned seal pups fed either artificial milk-replacer or fish-formula. Pups admitted to the facility in summer 2007 (n=145) and 2008 (n=98) were randomly assigned to one of two diets and fed by gavage until weaning. In 2007, pups fed milk-replacer gained more (43 ± 12 g/d) than those fed fish-formula (loss of 13 ± 6 g/d; P<0.002). In 2008, when intake was increased from 8 to 11% of body weight daily, weight gain improved for both diets but remained higher in pups fed milk-replacer (123 ± 12 g/d, vs. loss of 6 ± 8 g/day; P<0.001). Pup survival to weaning was significantly higher in 2008 than 2007 (P<0.001) and was higher for pups on milk-replacer compared with those on fish-formula (P<0.05). Survival was also correlated with body weight at admittance (P<0.001). Although neither diet achieved the weight gains recorded in mother-raised pups (400-800 g/d), the artificial milk-replacer was clearly more successful, and pups fared better in the second year of the study when intake was higher.     

Oxygen consumption and survival prediction in neonatal rats exposed to prenatal hypervitaminosis A

Fetal exposure to excess vitamin A results in a highly variable degree of lung pathology and high neonatal mortality in the Long-Evans rat. The present study evaluated O2 consumption in newborn of vitamin A-treated, vehicle-treated, and untreated pregnancies on five consecutive postnatal days beginning with the day of delivery (D0). Pregnant female rats were treated by gavage with 160,000 USP units of retinyl acetate dissolved in 0.5 ml corn oil on days 15 through 19 of gestation. Vehicle and undisturbed controls were run concurrently. All animals delivered spontaneously, and the pups were tattooed and individually tested in a closed system consisting of three chambers submerged within a thermostatically controlled water bath at 33 degrees C. Vitamin A-exposed pups, as a group, have significantly lower QO2 (ml O2 consumed/min/kg body weight) values than controls through postnatal day 2 (p less than 0.05). By days 3 and 4 of age, the mean QO2 values of surviving vitamin A-treated pups were similar to those of controls. A QO2 of 30 or greater on day 0 appears to be critical for early neonatal survival of vitamin A-exposed pups, as 87% of the pups with initial QO2 less than 30 died prior to day 4. Oxygen consumption rates in teratogen-exposed pups exhibiting low QO2 on day 0 rarely reached normal levels. In contrast, the occasional control pup with such low initial levels were well within normal limits (means +/- 1 SD) by the following day.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term effects of postovulatory aging of mouse oocytes on offspring: a two-generational study.

Aims of this study were to analyze the long-term effects of postovulatory aging of mouse oocytes on 1) reproductive traits of parental (F(0)) and first (F(1))-generation females (pregnancy rate, gestation length, litter size, perinatal death, and sex ratio of offspring) and 2) developmental and behavioral variables of F(1) and second-generation (F(2)) offspring (birth weight and weight gain during preweaning development, postnatal day of attainment of immediate righting, spontaneous motor activity, and passive and active conditioned learning ability). Hybrid (C57BL/6JIco x CBA/JIco) females were artificially inseminated at 13 h (control group) or 22 h (oocyte-aged group) after GnRH injection. Experimental (oocyte-aged group) F(0) females exhibited lower pregnancy rate, shortened gestation length, decreased litter size, higher perinatal death of their pups, and increased percentage of male offspring compared to control F(0) females. Postovulatory aging of oocytes was also associated with increased number of growth-retarded pups, delayed development of the righting reflex, and higher spontaneous motor activity and emotionality of F(1) offspring. Postovulatory aging of F(0) oocytes did not affect birth weight, weight gain during preweaning development, passive and active conditioned learning ability of F(1) offspring, or reproductive traits of F(1) females or developmental and behavior variables of F(2) offspring.     

Effect of diet with different protein content on rats during gestation: repercussion on pregnancy development and litter size. Preliminary note

Pregnant rats, Wistar strain, were treated from day 11 of gestation with synthetic diets containing different amounts of protein. The Group of rats fed a severely deficient protein diet (4% of casein, 2% of lactalbumin) showed reduced hematocrit, hemoglobin, total protein and an expressive increase of gamma globulins compared with rats treated with normal or elevated protein levels. Weight gain during pregnancy was higher for rats which received a larger amount of protein; on the contrary those that were subjected to malnutrition had no weight gain and bore prematurely with high percent of foetal mortality.     

Malnutrition in utero and lactation: relation between the weight gained by the mothers and the development of their offspring

Physiological weight changes in rat dams and their offspring as sequelae of malnutrition during pregnancy and lactation have been studied. Daily monitoring of the body weight as well as the consumption of food (malnutrition dams 14 g during pregnancy and 20 g during lactation) and drink in control and malnutrition dams was conducted. The number of pregnant dams that completed their pregnant period successfully was registered as well as the number and weight of the pups at birth and their evolution over a period of a month. The percentage of mortality of the pups during that period has been studied. The present results indicate a highly significant decrease in body weight in experimental dams, which determines a retardation in the physiological development of the pups, and yields a higher percentage of mortality in the experimental animals than in controls. It can thus be concluded that malnutrition in utero and during lactation affects the ratio between weight gain for dams and the physical development of their pups.     

Neonatal behavioral toxicity in rats following prenatal exposure to methanol

Although methanol (MEOH) may assume a significant role as a fuel, which implies wide availability, little is known of its toxicity apart from acute poisoning episodes in human adults. Even less is known about its toxicity in developing organisms. This experiment studied the early behavioral development of rats whose mothers had consumed MEOH during gestation by measuring the responses of suckling (postnatal day 1) and nest-seeking (postnatal day 10). Primigravida Long-Evans rats were divided into three groups (N = 10). Two of the groups consumed drinking solutions of 2% MEOH instead of distilled water either on gestational days 15-17 (MEOH 1) or 17-19 (MEOH 2). No maternal toxicity was apparent as measured by weight gain, gestational duration, and daily fluid intake. Daily MEOH consumption averaged 2.5 gm/kg over the 3-day period in both MEOH groups. Litter size, birth weight, and infant mortality did not differ among the three groups. Postnatal growth and date of eye opening were unaffected. MEOH pups required longer than controls to begin suckling on postnatal day 1. On postnatal day 10, they required more time to locate nesting material from their home cages. These data suggest that prenatal MEOH exposure induces behavioral abnormalities early in life that are unaccompanied by overt toxicity.     

Grey seal, Halichoerus grypus, energetics: females invest more in male offspring

Grey seal females transfer large amounts of energy to their pups during the brief lactation period. The costs of lactation have been measured using weight changes of mother and pup pairs. Large females come ashore to give birth earlier in the season and lose weight more rapidly than smaller females. The sex ratio of Grey seal pups born is skewed towards males in the early part of the breeding season. Male pups are larger at birth and gain weight more rapidly than female pups, and their mothers show a correspondingly faster rate of weight loss than mothers of female pups. The energy costs of gestation and lactation to a Grey seal mother are 31 GJ for male pups and2–8 GJ for female pups. Males are therefore 10% more costly in energy terms to raise to weaning. Because, on average, large females arrive at breeding sites before smaller animals, biased results on weight changes would be obtained from methods which do not use repeated weighings. We suggest that the high efficiencies of lactation estimated for Harp seals compared with other phocid seals could be accounted for by such a bias.     

Fertility,Gestation Outcome and Parasite Congenital Transmissibility in Mice Infected with TcI,TcII and TcVI Genotypes of Trypanosoma cruzi

This work aims to compare the effects of acute or chronic infections with the T. cruzi genotypes TcI (X10 strain), TcII (Y strain) and TcVI (Tulahuen strain) on fertility, gestation, pup growth and the possible vertical transmission of parasites in BALB/c mice. The occurrence of congenital infection was evaluated by microscopic examination of blood and/or qPCR on blood and heart in newborn pups and/or older offspring submitted to cyclophosphamide-induced immunosuppression in order to detect possible cryptic congenital infection. Altogether, the results show that: i) for the three strains tested, acute infection occurring after the embryo implantation in the uterus (parasite inoculation 4 days before mating), or close to delivery (parasite inoculation on day 13 of gestation), prevents or severely jeopardizes gestation outcome (inducing pup mortality and intra-uterine growth retardation); ii) for the three strains tested, gestation during chronic infection results in intra-uterine growth retardation, whereas re-inoculation of TcVI parasites during gestation in such chronically infected mice, in addition, strongly increases pup mortality; iii) congenital infection remains a rare consequence of infection (occurring in approximately 4% of living pups born to acutely infected dams); iv) PCR, detecting parasitic DNA and not living parasites, is not convenient to detect congenial infection close to delivery; v) transmission of parasites by breast milk is unlikely. This study should encourage further investigations using other parasite strains and genotypes to explore the role of virulence and other factors, as well as the mechanisms of such effects on gestation and on the establishment of congenital infection.     

Central blockade of oxytocin receptors during mid-late gestation reduces amplitude of slow afterhyperpolarization in supraoptic oxytocin neurons

The neurohypophysial hormone oxytocin (OT), synthesized in magnocellular paraventricular (PVN) and supraoptic (SON) nuclei, is well known for its effects in lactation. Our previous studies showed that central OT receptor (OTR) binding is increased during gestation and that blockade of central OTRs, specifically during mid-late gestation, causes a delay in OT release during suckling and reduces weight gain in pups, suggesting decreased milk delivery. In the present study, we tested whether central OTR blockade during late gestation disrupts the gestation-related plasticity in intrinsic membrane properties. Whole cell current-clamp recordings were performed in OT neurons from pregnant rats (19-22 days in gestation) that were infused with an OTR antagonist (OTA) or artificial cerebrospinal fluid (aCSF) and from virgin rats infused with aCSF into the third ventricle via an osmotic minipump beginning on days 12-14 of gestation. The amplitudes of both Ca(2+)-dependent afterhyperpolarizations (AHPs), an apamin-sensitive medium AHP (mAHP) and an apamin-insensitive slow AHP (sAHP), were significantly increased during late gestation in control pregnant animals. However, the amplitude of the sAHP from pregnant rats treated with the OTA was significantly smaller than that of pregnant control rats and similar to that of virgins. These results indicate that the diminished efficiency in lactation due to OTR blockade may be partly a result of an altered sAHP that would shape OT bursting. These findings suggest that central actions of OT during late gestation are necessary for programming the plasticity of at least some of the intrinsic membrane properties in OT neurons during lactation.