Pup Mortality Research Articles

Interruption of parturition in rats by morphine: a result of inhibition of oxytocin secretion.

Oxytocin secretion is inhibited by opioids, and oxytocin is important in parturition. The effects on parturition of morphine, a relatively selective mu-opioid receptor agonist, were studied in the rat. Morphine or vehicle with or without the opiate antagonist naloxone were administered immediately after the birth of the second pup and the subsequent course of parturition was recorded in a total of 80 rats. Both s.c. morphine (10 mg/kg) and intracerebroventricular (i.c.v.) morphine (18 micrograms through a previously implanted cannula) interrupted parturition, delaying the birth of the sixth pup after treatment to 187.3 +/- 35.9 (S.E.M.) min and 195.4 +/- 19.5 min respectively, compared with 46.4 +/- 3.7 and 66.1 +/- 17.5 min after vehicle alone. The dose of morphine given i.c.v. had no effect when given s.c. Naloxone given concurrently prevented the effects of morphine. Eventually the rate of parturition in the morphine-treated groups recovered. Perinatal pup mortality rate was not increased when morphine was given to the mothers, but it did inhibit the expression of normal intrapartum maternal behaviour. Pup mortality was increased 48 h post partum by morphine given during parturition, and it reduced the proportion of rats with normal maternal behaviour 24 h post partum. Morphine did not affect spontaneous or oxytocin-stimulated contractile activity of the parturient uterus in vitro. The concentration of oxytocin in trunk blood plasma was decreased 40 min after i.c.v. morphine (24.3 +/- 3.9 vs 39.3 +/- 6.5 pmol/l in controls), as was vasopressin (7.2 +/- 1.5 vs 19.7 +/- 4.5 pmol/l in controls). Intravenous infusion of oxytocin (2-5 mU/min for 144.3 +/- 8.2 min; total infused 448.5 +/- 61.9 mU) after i.c.v. morphine re-started parturition; all pups were born to these rats (mean time to pup 6, 110.3 +/- 12.7 min) before the i.v. vehicle-infused rats given i.c.v. morphine re-started (mean time to pup 6, 406.3 +/- 125.2 min). It is concluded that morphine given during parturition acts centrally through opioid receptors to inhibit oxytocin secretion, and impairs the expression of maternal behaviour. Reversal of the effects of morphine on parturition by i.v. oxytocin demonstrates the important role of oxytocin in fetus ejection and expulsion.

Prenatal or postnatal exposure to bis(tri- n-butyltin)oxide in the rat: Postnatal evaluation of teratology and behavior

The results of a series of screening tests to determine the potential teratogenicity and neurotoxicity of developmental exposure to TBTO in rats are presented in this paper. For prenatal exposure, pregnant Long Evans rats were intubated with 0–16 mg/kg/day bis(tri- n-butyltin)oxide TBTO from Days 6 to 20 of gestation (GD 6–20). For postnatal exposure, rat pups were intubated with 0–60 mg/kg TBTO on Postnatal Day 5 (PND 5). Following prenatal exposure, dams were allowed to litter and pups were evaluated using a postnatal teratology screen. Postnatal evaluation for both exposures included motor activity (PND 13–64), the accustic startle response (PND 22–78), growth, and brain weight. The maximally tolerated dose (MTD) in pregnant rats was 5 mg/kg/day, which is one-third the MTD in nonpregnant rats. There were decreased numbers of live births, and decreased growth and viability at dosages ≥10 mg/kg/day. Cleft palate was found in 3% of the 12 mg/kg/day group. There was mortality following postnatal exposure to 60 mg/kg and all prenatal dosages ≥10 mg/kg/day. Preweaning body weight was significantly decreased for all postnatal dosages, and all prenatal dosages >2.5 mg/kg/day. Body weight reductions persisted to the postweaning period only in the high dose groups (10 mg/kg/day and 60 mg/kg). Behavioral evaluation demonstrated transient alterations in motor activity development (prenatal exposure only) and the acoustic startle response (postnatal exposure only). Persistent behavioral effects were observed only at dosages that produced overt maternal toxicity and/or postnatal mortality. The demonstration of the teratogenic and neurotoxic potential of TBTO in rats is confounded by associated maternal toxicity and/or pup mortality.

Effects of ivermectin on reproduction and neonatal toxicity in rats

In this study we describe the effects of ivermectin (MK-0933) on the reproduction and neonatal toxicity of several generations of rats. Ivermectin was administered orally at dose levels of 0.05, 0.1, 0.2, 0.4, 1.2 or 3.6 mg/kg body weight/day. An increase in postnatal pup mortality up to approximately day 10 post-partum and a decrease in pup weights in the surviving offspring compared with those of the control groups indicated that ivermectin was toxic to neonatal rats at doses as low as 0.4 mg/kg body weight/day. Cross-fostering of the rats indicated that the neonatal toxicity was related not to in utero exposure but to postnatal exposure through maternal milk. Subsequent studies with tritiated ivermectin administered orally to rats showed that levels of radioactivity in maternal milk were 3–4-fold higher than those in the plasma, which resulted in significantly higher levels of ivermectin in the brain and plasma of nursing offspring. The period of enhanced neonatal sensitivity (up to approximately day 10 post-partum) correlates with increases in the plasma—brain ratios of total radioactivity in offspring from approximately 1 on day 4 post-partum to approximately 3 on day 10 post-partum. This is consistent with the postnatal formation of the blood—brain barrier in this species. In other mammalian species, including humans, sheep and rabbits, the blood—brain barrier is formed pre-natally. Therefore, the neonatal toxicity of ivermectin in rats is probably the result of a combination of excessive exposure through maternal milk and the increased permeability of the blood—brain barrier during the early postnatal period in this species.

Effects of environment on grey seal (Halichoerus grypus) pup mortality. Studies on the Isle of May

Breeding sites, including beach environment and topography, play a significant role in the causes of death of grey seal (Halichoerus grypus) pups, in particular the incidence of starvation, peritonitis/navel ill, other infectious diseases and injuries as a result of adult‐pup interactions. The bacteria involved are opportunistic invaders. A wide and differing sex ratio in dead pups was found on different beaches and this has not been satisfactorily explained.

Copper-carbohydrate interaction in maternal, fetal and neonate rat

The present study was undertaken to determine whether the same type of interaction between dietary fructose and copper that affects young growing male rats also affects the fetus and the neonate. Female rats were fed copper-deficient (0.6 μg Cu/g) or adequate (6.0 μg/g) diets containing 62% carbohydrate as fructose or starch either for 8 weeks prior to conception, and during mating, gestation and lactation, or just during gestation. Fetuses were killed at days 14, 18 or 21 of gestation and newborn pups were killed at days 0, 10, or 21 postpartum. Regardless of the duration of dietary copper deprivation, feeding the fructose diet deficient in copper during pregnancy resulted in either fetal resorption or mortality of all newborn pups during the first few hours postpartum. In contrast, copper-deficient rats fed the starch-containing diets delivered live pups. However, 40% of their pups died during the first 2 days postpartum and occurred only when dams had been fed the deficient diet for 12–13 weeks. When fed the deficient diet for a total of 3 weeks only, during pregnancy, all copper-deficient rats fed starch delivered live pups and no mortality occurred during the lactation period. Feeding the copper-adequate fructose diet during lactation resulted in a lower hepatic copper concentration of suckling pups compared with starch feeding. Female pups had higher levels of copper and iron than male pups. The data show that fetal resorption and mortality of the neonate pup was dependent on the type of dietary carbohydrate fed to copper-deficient animals during pregnancy.

Long-term effects of lactational zinc deficiency on bone mineral composition in rats fed a commercially modified Luecke diet

The purpose of this study was threefold: 1. to determine the long-term effects of interactions between lactational zinc deficiency and gender on bone mineral composition in repleted rat offspring, 2. to determine the nutritional efficacy of the second of two commercially designed, modified Luecke diets (ML2) during the gestational and lactational stress, and 3. determine the ultratrace element contents of Ralston Rodent Laboratory Chow #5001. The ML2 basal diet, based on dextrose, sprayed egg white, and corn oil contained 0.420 micrograms Zn/g, was supplemented with Zn (as zinc acetate) at 0 (diet 0ML2) or 30 (diet 30ML2) micrograms/g, and was mixed and pelleted commercially. All rat dams were fed the 30ML2 diet ad libitum during gestation. Beginning at parturition, the dams were fed either the 1. 0ML2, 2. 30ML2 (food restricted), or 3. 30ML2 (ad libitum) diets. All pups were fed the 30ML2 diet ad libitum from 23 to 40 d of age. From d 40 to 150, all pups were fed Ralston Rodent Laboratory Chow. The 30ML2 diet was found to be nutritionally efficacious; litter size and pup growth were normal and pup mortality was only 1.2%. Pups (ZD) with access to the 0ML2 diet until 23 d of age and nursed by dams fed the 0ML2 diet, when compared to pups (PF) fed restricted amounts of the 30ML2 diet, exhibited increased mortality and decreased concentrations of tibial zinc but no change in growth. Inadequate zinc nutriture during infancy, despite postlactational zinc repletion, induced imbalances in adult bone mineral metabolism. Thus, at 150 d of age, the ZD pups exhibited increased levels of bone P and Mg and decreased concentrations of K as compared to the PF pups.

Effects of perinatal ivermectin exposure on behavioral development of rats

The antiparasitic agent ivermectin was administered to pregnant rats from days 6 to 20 of gestation and 2 to 20 of lactation at 1, 2 or 4 mg/kg/day. Reproductive performance and behavior of offspring in the preweaning period were observed. Ivermectin had no effect on reproductive performance and dams' growth. The highest dose induced 100% pup mortality. Later on, ivermectin at 4 mg/kg was administered only during gestation. At that dose, the drug induced 22% mortality and affected temporarily cliff avoidance, locomotion, negative geotaxis and swimming development. At 2 mg/kg, the drug induced offspring mortality (31%), retarded growth and delayed eye opening, cliff avoidance and surface righting reflex, negative geotaxis, locomotion and swimming development. Ivermectin at 1 mg/kg had no effect on mortality and growth but cliff avoidance and locomotion were retarded. Data suggest that newborn rats were highly susceptible to the neurotoxic action of ivermectin. Whether its effects were prenatal or by acute intoxication via mother's milk are discussed.

Role of dam and pups in the absence of nursing in CPB-B rats (rattus norvegicus)

In rats of the CPB-B strain, the female shows normal parturition behaviour and normal capacity of milk secretion, but the young - all born alive - die within few days of birth. Here, we report that this postnatal mortality is eliminated when CPB-B neonates are crossfostered to mothers of the Wu:Cpb strain; conversely, Wu:Cpb neonates (which are successfully reared by dams of their own strain) die within few days of birth when crossfostered to newly parturient CPB-B rats. It is suggested that pup mortality in CPB-B rats is due to inadequate maternal care resulting, supposedly, from susceptibility of the mother to disturbing environmental stimuli.

V. Human Predation on The Dingo

The scalp bonus certificates of 18 614 dingoes destroyed on the mid-north coast of NSW between 1958 and 1983 were examined. Annual scalp returns were highest in 1961 (1546), fell to 256 by 1974 then rose to 475 by 1983. The decline was associated more with a reduction in the area from which dingoes were taken rather than a reduced offtake from the overall area. Half the dingoes were taken by trapping and 37% were shot, although shooting, which was more opportunistic than trapping, became relatively more common during the period. The sex ratio of the dingoes killed was strongly biased towards males but there was evidence that this reflected the sex ratio in the dingo population. We suggest that the bias arose from higher natural mortality of female pups associated with their smaller size.The number of hunters declined during the study. On average, each operated for 2.3 years (range 1-22) and killed 6.4 dingoes (range 1-231). A small group of hunters made a significant contribution to the total scalp take over time and there was some evidence of harvesting amongst this group. Two-thirds of the scalps were taken by property owners or their relatives and only 22% by hunters with no obvious association with the land on which they hunted. Because of this and the lack of any relationship between the cash value of the bonus and scalp returns, the value of the bonus system as an incentive to control dingoes is questionable.

Effects of gamma-linolenic acid supplementation on pregnant rats fed a zinc-deficient diet.

The effects of dietary gamma-linolenic acid supplementation in the form of evening primrose oil were examined in pregnant zinc-deficient rats and subsequently in their newborn pups. This supplementation was beneficial, since it reduced pup mortality, increased mean litter size and maintained appetite throughout two thirds of the gestation period. Consequently, gamma-linolenic acid seems to correct some of the biological effects of zinc deficiency. It is suggested that evening primrose oil could be used in cases of zinc deficiency caused by metabolic disturbances.

The effects of energy intake during pregnancy in doe rabbits on pup birth weight, milk output and maternal body composition change in the ensuing lactation

SUMMARYA study was made in rabbits on the effects of energy intake during pregnanoy on pup birth weight and survival, and on doe body composition and milk output in the ensuing lactation. In addition the experiment examined the effects of varying crudeprotein intakes during lactation on the rate of fat loss of does and the resultant energetic efficiency of milk production.Forty-seven multiparous cross-bred does were used. They were offered one of two diets in pregnancy, either diet HE (14·8 MJ digestible energy (DE)/kg D.M.) to appetite or diet LE (12·9 MJ DE/kg D.M.) at maintenance levels. After parturition seven does on each treatment were slaughtered and their body composition analysed (control groups). In lactation the remaining does were evenly allocated to receive either diet LE (195 g crude protein (CP)/kg D.M.) or diet HP (240 g CP/kg D.M.) to appetite. Litter sizes were standardized to six pups and litter growth rates were used as an indirect estimate of milk production. Does were then killed, at random, on day 9 or day 18 of lactation to give an estimate of changes in body composition as lactation progressed.Does offered diet HE during pregnancy had higher carcass fat levels at parturition than their counterparts offered diet LE (496 cf. 370 g/kg carcass D.M. respectively). Litter size was unaffected by dietary treatment during pregnancy but litter weights at birth were significantly greater in HE does (442 cf. 398 g respectively). Pup mortality at birth, however, was also much higher in these animals (28 cf. 9% respectively). Voluntary food intake in early lactation (day 1—9) was depressed by feeding diet HE during pregnanoy. Milk composition was affected by pregnancy diet, with does offered diet HE producing milk containing significantly higher fat levels (HE 123 g fat/kg milk cf. LE 105 g fat/kg milk).Doe carcass composition changes revealed that fat was usually mobilized in early lactation and gained as lactation progressed independent of dietary treatment. The protein content of the fat-free dry matter appeared to be relatively unaffected by the dietary treatments imposed. The data were used to derive an estimate of the partial efficiency of dietary energy utilization (fc) for milk output and maternal tissue gain. The line of best fit was described by the equation ER = 0·65 (±0·17) MEI-1–25, where ER = milk energy output + carcass energy change and MEI = metabolizable energy intake in MJ.

Effects of chronic ingestion of caffeine on mammary growth and reproduction in mice

Normal mammary gland growth and reproduction were examined in C3H/HeMei mice given caffeine as drinking water (500 mg/1 tap water) after weaning on day 20 of age. Caffeine ingestion had little effects on any of the day of vaginal opening, body growth, pattern of estrous cycles, mammary gland growth and reproduction except for the rearing rate on day 12 of lactation. Five out of 12 mothers given caffeine lost all pups before day 12 and resulted in 51 % of the rearing rate on that day, while that of the control was 91 %. The rate did not change thereafter in either group. The results indicate that the chronic heavy ingestion of caffeine would induce the high mortality of pups during early stage of lactation.

Sex ratio shifts within litters of meadow voles (Microtus pennsylvanicus)

Changes in the sex ratio of juvenile recruits into a population of meadow voles (Microtus pennsylvanicus) were correlated with shifts in the weight and mortality of pups within the population. The biased recruitment of female juveniles in the spring was reflected in differential allocation of energy within the litters, as measured by female pups being heavier than male pups (n=245). In the fall, the shift in recruitment to male juveniles was reflected within litters by male pups being heavier than female pups (n=139). Nestling mortality showed a similar gender bias. Skewed sex ratios were most evident within the litters of larger mothers, indicating the gender bias was not trigered by energy limitations. We postulate that gender differences in social spacing and behavior result in spring/fall fluctuations in the reproductive success of offspring, based on their gender.

Reproductive, immunologic, and cytogenetic effects of dietary 3,3',4,4'-tetrachloroazoxybenzene exposure to mice.

The effects of chronic dietary exposure to 3,3′,4,4′-tetrachloroazoxybenzene (TCAOB) on the reproductive efficiency of female Swiss-Webster mice were measured. The immunocompetence of their offspring was assayed at weaning. No indications of toxicosis were seen in the adult females with the exception of a reduction in the thymus weight of the animals consuming 10 ppm TCAOB. Pup mortality to weaning and the percentage of females whelping were not affected by 0.1 ppm, 1 ppm, or 10 ppm of TCAOB in the diet. There was, however, a significant reduction in the number of pups (at birth and at weaning) per female whelping at 10 ppm TCAOB in the diet. The thymus weight and plaque-forming-cell response of the pups were also significantly reduced below control levels. The lymphocyte blastogenic response to Concanavalin-A and lipopolysaccharide, and total peripheral blood leukocyte count, were not affected by the concentrations of TCAOB tested. Dietary treatment of female mice with relatively high concentrations of this chemical resulted in reduced reproductivity capacity, but only moderate immuno-suppression of their offspring exposed duringin utero and early postnatal development.

Mortality of northern fur seal pups in relation to growth and birth weights.

Mortality of northern fur seal pups in relation to growth and birth weights.

ラット胎性期に暴露した自律神経作用薬の子の行動発達に及ぼす影響

The drugs used were methamphetamine, reserpine, norepinephrine, epinephrine, propranolol, chlorpromazine, haloperidol, pilocarpine and atropine. Each drug except for reserpine (days 7-13 and 14-19 of gestation) was administered subcutaneously to dams from day 7 to 19 of gestation. The body weight gain of dams receiving reserpine (days 7-13) and haloperidol was inhibited during the gestation period. Two out of 9 dams receiving methamphetamine died on day 21 of gestation period; However, no effect was observed in dams given other drugs. The body weight gain of pups was inhibited in methamphetamine and haloperidol treated groups. The mortality of pups was comparable in all groups. The behavioral development of the righting reflex, cliff drop avoidance and negative geotaxis of pups given reserpine (days 7-13), norepinephrine, chlorpromazine and haloperidol was significantly retarded in comparison with that of control pups. The spontaneous motor activity of pups measured by Animex was increased in reserpine (days 7-13) and epinephrine treated groups and decreased in the chlorpromazine treated group on day 28 postpartum, but comparable in all groups on day 56 postpartum. The conditioned avoidance responses using the shuttle box revealed deficits of avoidance learning of pups in the reserpine (days 7-13), norepinephrine and atropine treated groups. These findings suggest that the prenatal exposure to drugs acting on the autonomic nervous system may produce adverse effects on the behavioral development of pups; However, the adverse effects were more apparent by postnatal exposure than by prenatal exposure.

The current status of the grey seal Halichoerus grypus in Cornwall, England

A survey of previously identified grey seal Halichoerus grypus breeding sites around the coast of Cornwall, England, was carried out during the 1982 pupping season. Adverse weather restricted survey operations and also probably resulted in a high, though not necessarily exceptional, pup mortality. There is no evidence of a change in status or distribution of the grey seal in Cornwall since the last survey in 1973, although observations suggest that the timing of the breeding season is earlier than previously calculated. Local information indicates that up to 40 pups are born each year, an estimate that would be refined by regular surveys of all the pupping sites throughout the breeding season, from early September to mid-October.

Behavioural effects of prenatal exposure to carbon disulphide and to aromatol in rats.

The neurotoxic effects of prenatal organosolvent inhalation were studied in rats, because of the expectation that a developing organism may be more sensitive than the adult to the induction of functional deficits. The aim was to determine whether prenatal exposure to the new organosolvent mixture, Aromatol, and the well known neurotoxic carbon disulphide, would impair reflex ontogeny or produce neurobehavioural dysfunctions in the offspring. Development of gait, motor coordination, and activity, avoidance learning and swimming were tested in the offspring of CFY rat mothers, exposed to CS2 inhalation (0, less than 10, 700 and 2000 mg/m3) and to Aromatol (0, 600, 1000 and 2000 mg/m3) on days 7-15 gestation. Prenatal CS2 inhalation induced dose related perinatal mortality of pups. Eye opening and the auditory startle were retarded. There were immature gait, motor incoordination, diminished open field activity and altered behavioural patterns on day 21 and 36 but they were nearly age-appropriate on day 90. As signs of disturbed learning ability, there were diminished performance and lengthened latency of the conditioned avoidance response, related to the concentrations administered. Contrary to expectations, prenatal Aromatol inhalation had no effect on maturation of gait, behaviour patterns, or learning ability.

Effects of mother-litter separation and reunion on maternal aggression and pup mortality in lactating hamsters

This study examined the effects of a 24 hr mother-litter separation on maternal aggression and pup mortality in hamsters. There were four lactating groups tested for aggression in their home cages on days 5 and 15 postpartum: a group that was separated from their litters for 24 hr, a group that was not separated from their litters and two 24 hr separation groups in which the litters were returned 30 and 120 min prior to the aggression test. Nonreceptive, estrous cycling animals were used as controls (tested twice, 10 days apart) and as intruders. Measures of aggression recorded during the 10 min tests included the number of attacks, fights, chases and intruder retreats. Pup mortality was examined in the 4 lactating groups and in two additional non-tested groups, one of which was separated from their litters for 24 hr. Lactating hamsters initiated significantly higher levels of aggression than control animals. Mother-litter separation (24 hr) significantly decreased levels of aggression and these levels were restored when litters were replaced 30 and 120 min prior to aggression tests. There were few differences in levels of aggression between days 5 and 15 of lactation. Pup mortality was significantly greater between days 5–6 and 15–16 of lactation among those groups that were separated from their litters compared to those groups that were not separated. Significantly higher mortality levels were found between days 7 and 15 of lactation among the 2 groups in which pups were returned prior to the aggression test compared to all other groups.

The effects of reducing the remating interval after parturition on the reproductive performance of the commercial doe rabbit

ABSTRACTFour groups of does (16 per group) were remated either 1, 7, 14 or 21 days after parturition over a 1-year production cycle. Doe mortality rate was independent of treatment and overall was 0·27. The remating interval after parturition had no effect on conception rate, which was high on all treatments (0·86 to 0·93). The high overall conception rate resulted in more litters being born as the parturition to remating interval decreased. Expressed on a common 365-day experimental period the number of litters per doe was 8·9, 8·5, 7·8 and 6·7 (average s.e. of difference 0·33) for treatments 1, 7, 14 and 21 respectively. Litter size was not significantly affected by treatment and consequently the number of pups born per doe per year increased as remating interval decreased: 75·0, 73·4, 67·4 and 591 respectively. Pup mortality rate at birth and subsequently was high (0·42) on all treatments and the number of pups weaned per doe per year for treatments 1, 7, 14 and 21 was 48·3, 43·5, 40·0 and 33·3 respectively. Pup birth weight, 21-day litter weight and weaning (25-day) weight were all unaffected by treatment, as was doe body-weight change.