Influence of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers: does otolith growth cease at low temperatures?

The influences of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers were investigated using individuals reared at 5, 10, 15, 20, 25 and 30° C and in fed or unfed conditions at salinity 32 after their otoliths were marked with alizarin complexone (ALC). To eliminate the difficulty of observing the edges of otoliths with optical (OM) or scanning electron (SEM) microscopes, three to 10 individuals were sampled from each tank at 10, 20 and 30 days during the experiment and reared for an additional 10 days at 25° C after their otoliths were marked a second time. Otolith growth and the number of increments were measured using both OM and SEM. Most A. japonica commenced feeding after 10 days at 20–30° C or after 20 days at 15° C, but no feeding occurred at 5 and 10° C. No otolith growth occurred at 5 and 10° C except in two individuals with minimal increment deposition at 10° C. Otolith growth was proportional to water temperature within 15–25° C and not different between 25 and 30° C. At 15, 25 and 30° C, the mean otolith growth rate in fed conditions was higher than in unfed conditions. The number of increments per day was significantly different among water temperatures (0·00–0·01 day⁻¹ at 5 and 10° C, 0·43–0·48 day⁻¹ at 15° C and 0·94–1·07 day⁻¹ at 20–30° C). These results indicated that otolith growth in A. japonica glass eels and elvers was affected by temperature and ceased at ≤10° C under experimental conditions. Hence, future studies analysing the otoliths of wild-caught A. japonica glass eels and elvers need to carefully consider the water temperatures potentially experienced by the juveniles in the wild.     

Effect of salinity and temperature on the growth of yearling Arctic cisco (Coregonus autumnalis) of the Alaskan Beaufort Sea

The growth of 1-year-old Arctic cisco ( Coregonus autumnalis ) was monitored under laboratory conditions for fish acclimated to one of two temperatures (5 and 10° C) and one of five salinities (6, 12, 18,24, 30‰). Fish were maintained for 43 days at rations of 3% wet body weight per day at 5° C and 5% wet body weight per day at 10° C, with rations adjusted for weight gain every 7–12 days. Fish increased 9–11% in length and 55–71% in weight at 5° C, and 23–27% in length and 141–161% in weight at 10° C. Length and weight increased linearly over 43 days. There was a statistically significant effect of temperature on growth but no statistically significant effect of salinity. Higher growth rates at 10° C were partially attributable to significantly greater gross conversion efficiency at the higher temperature. Over the course of the experiment, the condition (weight per unit length) of all fish increased by 3·2 to 63·6% at 5° C and by 5·6 to 46·0% at 10° C. There was no discernible effect of salinity on condition at either temperature. These results demonstrate that, with salinity acclimation and high food ration, 1-year-old Arctic cisco can grow at equivalent rates across salinities ranging from 6 to 30‰. The ecological implications of the results are discussed.     

Influence of level of nutrition during late pregnancy on reproductive productivity of red deer (2) Adult hinds gestating wapitixred deer crossbred calves

The present study aimed to relate feed intake of red deer hinds in the later stages of gestating wapitixred deer crossbred foetuses on dam body condition, gestation length, birth weight and calf growth. Multiparous hinds (N=18) conceiving at known dates to either wapiti (n=12) or red deer (n=6) sires were housed in individual pens from days 150-220 of pregnancy, during which time they were offered either ad libitum access to pelletised rations (n=6 crossbred-bearing hinds [HH] and n=6 red deer-bearing hinds [RH]) or a restricted offer (n=6 crossbred-bearing hinds [HL]) set at 70% of the average ad libitum intake of HH hind in the previous week. Hinds were returned to pasture at day 220 and calving was closely monitored. Liveweights, body condition score (BCS), and lactation score (LS) of hinds were recorded weekly from day 130 of pregnancy until calves were weaned at 12 weeks of age. Calves were tagged and weighed at birth, and subsequently weighed at 7 and 12 weeks of age. HH and RH hinds exhibited similar patterns and levels of MEI/kg0.75, which peaked at 7.8 MJME/kg0.75 at day 220. HL hinds peaked at approximately 5 MJME/kg0.75 and showed significantly lower rates of liveweight gain during pregnancy. Interestingly, both crossbred-bearing groups initiated mammary development in advance of the RH hinds. While there were significant effects of foetal genotype on mean gestation length (239 days versus 234 days for crossbred versus red deer) and mean birth weight (14.5 kg versus 10 kg), the nutritional contrast for gestation length of crossbred-bearing hinds (i.e. HH versus HL) was not significant but approached significance for birth weight (14.5 kg versus 11.9 kg; P=0.06). Regression analysis revealed weak relationships between changes in hind liveweight and gestation length (P>0.05) but a significant relationship with birth weight (P<0.05). However, change in hind BCS was significantly related to both gestation length and birth weight. Crossbred calves reared by HH hinds were 30% heavier at 7 and 12 weeks of age than the red deer calves. However, those reared by HL hinds were significantly lighter than their genotype contemporaries and only marginally heavier than the red deer calves. These results generally contrast with the previous studies on red deer hinds gestating red deer foetuses [Asher, G.W., Mulley, R.C., O'Neill, K.T., Scott, I.C., Jopson, N.B., Littlejohn, R. 2004. Influence of level of nutrition during late pregnancy on reproductive productivity of red deer, (1) Adult and primiparous hinds gestating red deer calves. Anim. Reprod. Sci., in press] and indicate that the genetically determined higher growth requirements of crossbred foetuses may override any mechanism of compensatory control of gestation length at the expense of calf birth weight. Furthermore, there were marked carryover effects of late gestational feeding on crossbred calf growth and their dam's BCS that highlight the high nutritional demands of lactation.     

Effect of maternal malnutrition on surface activity of fetal lungs in rats.

The effects of maternal malnutrition on fetal lung growth and surface forces were studied in albino rats. Pregnant albino rats were subjected to one of the following diets: rat chow ad lib. (controls), partial food deprivation (intake one-half that of the controls), complete food deprivation for 4 days (on gestation day 3-7, 9-13, or 17-21), low protein (8%), and fat free. The fetal lungs were studied on the 21st day of gestation (delivered by cesarean section) or at birth (gestation day 22). Fetuses and neonates after maternal food deprivation (FD) on the 17-21 day of pregnancy, and after a low-protein (LP) diet during pregnancy, had significantly smaller body weight and lung wet or dry weight/body weight ratio (hypocellular lungs). The minimum surface tension (gamma min) of fetal lung extracts was significantly increased with FD and LP. This was associated with a reduction of about 35% in lung lecithin content, expressed per lung DNA. The earlier in pregnancy the rat was subjected to 4-day food deprivation the less the effect on the fetus. At birth the gamma min and the lung lecithin content reached control values. This recovery occurred after birth (at age 4-10 h) and prior to first feeding. However, the lungs remained small and hypocellular. The results indicate that the nutritional status of the pregnant rat influences the surface activity and the growth of the fetal lung.     

A reproductive study of Weiser-Maples guinea pigs]

The Weiser-Maples (WE) guinea pig strain was introduced by Backshire Co., Ltd. (USA) in 1977. We have been breeding WE strain guinea pigs for skin melanization research. The WE guinea pig colony produced 1271 pups in 417 litters from May 1978 through December 1983. Breeding date are shown below. The mean litter size was 3.05, the stillborn rate was 15.2%, the weaning rate for live-born pups was 93.5% and the sex ratio was 1.01. The average age at first vaginal membrane rupture was 31.4 days at which time body weight was 290.5g. The mean length of the first 7 estrous cycles was about 17 days, with no cyclical variation in length. The mean duration of gestation was 67.9 days. Duration of pregnancy varied with litter size. There was an inverse relationship between litter size and duration of pregnancy. Most of the pups were delivered alive in mid-pregnancy with a parturition range of 56 to 76 days. The probability of pup death depends on gestational length: the lowest incidence of mortality was seen in litters born at 70 days. The mortalities were related to litter size but not to parity. There was an inverse relationship between birth weight and litter size. In WE guinea pigs, the mean weight for a litter of 1 was 120 g; for a litter of 5, the mean body weight was 58g. Male body weights were slightly heavier than female at birth and at weaning age. The mean body weights are shown below, date of birth: female 88.3g, male 93.3g, weaning age (2 weeks): female 181.1g, male 198.8g and 30 weeks: female 758.7g, male 1018.0g. These date for WE guinea pigs are comparable to those of other strains.     

Relationships between fetal biometry, maternal factors and birth weight of purebred domestic cat kittens

The goal of this study was to evaluate the relation between kittens' birth weights and biometrical factors from the kittens and the mother during pregnancy. Knowing fetal birth weight could help in detecting abnormalities before parturition. A Caesarean-section or a postnatal management plan could be scheduled. Consequently, the neonatal mortality rate should be decreased. We used ultrasonographic measurements of femur length (FL) or fetal biparietal diameter (BPD), pregnancies, and maternal factors to obtain a model of prediction. For this purpose, linear mixed-effects models were used because of random effects (several fetuses for one queen and a few paired measurements) and fixed effects (litter size, pregnancy rank, weight, wither height, and age of the queen). This study was performed in 24 purebred queens with normal pregnancies and normal body conditions. Queens were scanned in the second half of pregnancy, using a micro-convex probe. They gave birth to 140 healthy kittens whose mean birth weight was 104 g (ranged 65 to 165 g). No correlation between the birth weight and the age of the queen, as a maternal factor alone, was observed. But the birth weight was found to be inversely proportional to the pregnancy rank and the litter size. Moreover, birth weight increased when the weight and wither height of queen increased. BPD and FL increased linearly during pregnancy so a model was used to estimate mean birth weight. Using this model, we found a correlation between mean birth weights and an association of parameters: maternal factors (wither height and age), and litter size.     

Relationships between fetal biometry,maternal factors and birth weight of purebred domestic cat kittens

The goal of this study was to evaluate the relation between kittens' birth weights and biometrical factors from the kittens and the mother during pregnancy. Knowing fetal birth weight could help in detecting abnormalities before parturition. A Caesarean-section or a postnatal management plan could be scheduled. Consequently, the neonatal mortality rate should be decreased. We used ultrasonographic measurements of femur length (FL) or fetal biparietal diameter (BPD), pregnancies, and maternal factors to obtain a model of prediction. For this purpose, linear mixed-effects models were used because of random effects (several fetuses for one queen and a few paired measurements) and fixed effects (litter size, pregnancy rank, weight, wither height, and age of the queen). This study was performed in 24 purebred queens with normal pregnancies and normal body conditions. Queens were scanned in the second half of pregnancy, using a micro-convex probe. They gave birth to 140 healthy kittens whose mean birth weight was 104 g (ranged 65 to 165 g). No correlation between the birth weight and the age of the queen, as a maternal factor alone, was observed. But the birth weight was found to be inversely proportional to the pregnancy rank and the litter size. Moreover, birth weight increased when the weight and wither height of queen increased. BPD and FL increased linearly during pregnancy so a model was used to estimate mean birth weight. Using this model, we found a correlation between mean birth weights and an association of parameters: maternal factors (wither height and age), and litter size.     

Association between postnatal catch-up growth and obesity in childhood: prospective cohort study

ObjectiveTo identify predictors of postnatal catch-up growth from birth to two years and its relation to size and obesity at five years.DesignRegional prospective cohort study.SettingAvon longitudinal study of pregnancy and childhood, United Kingdom.Subjects848 full term singletons from a 10% random sample of the Avon longitudinal study of pregnancy and childhood.ResultsSize at birth was representative of the national reference. Overall, 30.7% (260 of 848) of infants showed a gain in SD score for weight greater than 0.67 SD scores between zero and two years, indicating clinically significant catch-up growth. These children had lower weight, length, and ponderal index at birth than other children, and were more often from primiparous pregnancies. They also had taller fathers than other children, and their mothers had lower birth weights and were more likely to smoke during pregnancy. Children who showed catch-up growth between zero and two years were heavier, taller, and fatter (body mass index, percentage body fat, and waist circumference) at five years than other children.ConclusionsIn this contemporary well nourished cohort, catch-up growth was predicted by factors relating to intrauterine restraint of fetal growth. Children who showed catch-up growth between zero and two years were fatter and had more central fat distribution at five years than other children. Mechanisms that signal and regulate early catch-up growth in the postnatal period may influence associations between small size at birth and risks for disease in adulthood.     

人工饲养条件下东方田鼠指名亚种繁殖特性及其幼仔的生长发育

在实验室饲养条件下, 对东方田鼠指名亚种繁殖特性和幼仔生长发育进行了初步观察。该鼠全年均可繁殖, 平均每胎产仔3.8 ±1.5 只, 妊娠期20～21 d , 繁殖间隔期39.3 ±26.4 d , 雌雄比为1.48。幼鼠3 日龄耳壳完全直立, 4 日龄开始长下门齿, 5 日龄长上门齿, 7～8 日龄睁眼, 20 日龄可断奶, 55 日龄左右性成熟。3 种生长模型(Logistic 方程、Gompertz 方程和Von Bertalanffy 方程) 对体重、体长、尾和后足的生长过程的拟合优度均很高,择优选用Von Bertalanffy 方程对体重、体长和尾长进行描述, 选用Logistic 方程对后足长的生长过程进行描述。将该鼠的生长发育过程划分为4 个阶段, 乳鼠阶段: 初生至10 日龄; 幼鼠阶段: 11 日龄至20 日龄; 亚成年阶段: 21至55 日龄; 成年阶段: 56 日龄以后。对指名亚种和长江亚种生长、繁殖特性异同亦作了初步分析。     

Genetic-statistical analysis of growth in selected and unselected mouse lines

The growth of males sampled from two mouse lines long-term selected for over 86 generations on body weight (DU6) or on protein amount (DU6P) was analysed from birth till 120 days of age and compared to the growth of an unselected control line (DUKs). Animals from the selected lines are already approximately 40 to 50% heavier at birth than the controls. This divergence increases to about 210 to 240% at the 120 day of age. With birth weights of 2.2 and 2.4 g and weights of 78 and 89 g at the 120 day these selection lines are the heaviest known mouse lines.

The fit of three modified non-linear growth functions (Gompertz function, Logistic function, Richards function) was compared and the effect of three different data inputs elucidated. The modification was undertaken to use parameters having a direct biological meaning, for example: A: theoretical final body weight, B: maximum weight gain, C: age at maximum weight gain, D (only Richards function): determines the position of the inflection point in relation to the final weight. All three models fit the observed data very well (r² = 0.949–0.998), with a slight advantage for the Richards function. There were no substantial effects of the data input (averages, single values, fitting a curve for every animal with subsequent averaging the parameters).

The high growth of the selected mice is connected with very substantial changes in the final weight and in the maximum weight gain, whereas the changes of the age at the point of inflection were, although partially significant, relatively small and dependent on the model used.     

Postnatal growth pattern of F1 hybrids of a cross between two strains of large and small musk shrews, Suncus murinus

In our previous comparison of the postnatal growth of two laboratory strains of the musk shrew (Suncus murinus), the large shrews originating in Bangladesh (BAN strain) and the small shrews from Nagasaki, Japan (NAG strain), we found that differences in the 120-day adult body weight of the two strains (BAN: males 135.3g and females 82.0g; NAG: 52.9 and 34.2g, respectively) reflect both an approximately 2.5 times longer linear growth phase and an approximately 1.5 times higher growth rate during this phase in the BAN strain. We examined the postnatal growth (from 5 to 120 days after birth) of the F1 hybrids of a cross between the two strains and compared our findings with the above-mentioned growth data for the parent strains. A growth equation composed of linear and monomolecular functions was fitted to the growth data for the shrews. The growth trajectories of both sexes of the F1 hybrids were situated roughly midway between those of the two parent strains throughout the entire growth process. The adult body weight of the F1 shrews at 120 days of age averaged 86.0g in the males and 51.7g in the females. The growth phase lasted approximately 60 days in the males and approximately 40 days in the females of both the F1 shrews and the parent strains. The duration of the linear growth phase of the F1 hybrids (29.8 days in the males and 19.0 days in the females), however, was approximately intermediate between the parent strains (BAN: males 33.4 days and females 26.1 days; NAG: 18.8 and 13.9 days, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of host stage and temperature on selected developmental parameters of the solitary endoparasitoid Meteorus gyrator (Thun.) (Hym., Braconidae)

Abstract:  The development of the solitary endoparasitoid Meteorus gyrator was compared in the six larval stages of its host, the tomato moth Lacanobia oleracea , and at five constant temperatures. The host instar at the time of parasitism had a marked effect on the larval developmental period of the parasitoid, such that larvae derived from eggs oviposited in first instar hosts took approximately 18 days to egress, whilst those derived from eggs oviposited in sixth instar hosts took <10 days. The weight of cocoons was greatest when oviposition was into final instar hosts, where female cocoons averaged 12.8 mg, and lowest in those derived from eggs oviposited into first instars (9.2 mg). The parasitoid's larval development rate in third instar hosts increased with temperature increments in a linear fashion up to 25°C , after which development times were only marginally increased. At 10°C, the mean larval development time was approximately 90 days and pupal development 35–40 days, whilst at 25°C development times were 10–11 days for larvae and 6–7 days for the pupae. In the majority of cases, overall development times were marginally longer (<1 day) in females than in males.     

Hsp70 is not a sensitive indicator of thermal limitation in Gadus morhua

The levels of heat‐shock proteins of the 70 kDa family (Hsp70s) were measured in different soft tissues of Atlantic cod Gadus morhua from different locations and after exposure to various thermal conditions: acute temperature increments (1° C day⁻¹), mid‐term (73 days at 4–15° C) and long‐term thermal acclimation (278 days at 8–15° C), and seasonal and latitudinal temperature variations (field samples). Tissue specific distribution patterns of Hsp70s were observed: liver > gills > red blood cells > brain > white muscle. Thus, different tissues may have required different levels of protection by Hsp70s, and possibly this was related to the rate of protein synthesis. There were no differences in tissue Hsp70s between Arctic cod populations (Arctic, i.e . Barents and White Seas, Norwegian coast, and North or Baltic Seas). No changes in Hsp70s levels were observed in response to temperature variation of any intensity (acute fluctuation or seasonal and latitudinal) within the range of physiological temperatures (4–15° C) in wild and laboratory Atlantic cod. This confirms previous observations that changes in Hsp70 caused by such temperature variation are often small in fishes. Probably, the constitutive level of Hsp70s in Atlantic cod was high enough to overcome potentially harmful effects of temperature variations within the physiological range. A suppressing effect of high temperature (15° C) has already been observed at a systematic level (as reduced rate of somatic growth), whereas it is not reflected in modified Hsp70s. Therefore, Hsp70s apparently played a secondary role in defining thermal tolerance limits in Atlantic cod. These conclusions are in line with a recent concept of thermal tolerance which indicated that the first line of thermal limitation in the cold and warm is a loss in aerobic scope.     

BODY TEMPERATURE IN THE NEWBORN SOUTHERN ELEPHANT SEAL, MIROUNGA LEONINA, AT MACQUARIE ISLAND

Newborn southern elephant seal pups were reported by Laws (1953) to be "to some extent poikilothermic at birth." Rectal temperatures of known age southern elephant seal pups were recorded during the 1985 pupping season at Macquarie Island. The mean pup rectal temperature was found to be 381°C ± 0.1°C SEM ( n = 131, range = 36.5°-39.1°C). Pups at two hours, six hours, and one day after birth had significantly higher rectal temperatures than pups two, three, or four days of age. Rectal temperatures of neonatal southern elephant seals were within the range observed for other pinnipeds, (but never as low as the 31°C previously observed for southern elephant seals at Signy Island in 1953). A significant though weak positive correlation was found between pup temperature and body weight. However, no correlation between pup temperature and age or any environmental factor was found. These observations demonstrated that southern elephant seal pups at Macquarie Island are homeothermic, rather than heterothermic from birth.     

Effects of cohort,sex, and birth date on body development of roe deer (Capreolus capreolus) fawns

We investigated the effects of the year of birth (cohort effect), sex and birth date on the variations observed in birth weight and postnatal growth rate in 209 newborn fawns marked during eight consecutive fawning seasons from a highly productive roe deer population under good nutritional conditions. Roe deer exhibited a fast body development with a birth weight of 1628 g and a postnatal growth rate of 139 g/day constant over the first 20 days of their life. As previously reported for dimorphic and polygynous ungulates, there was a marked cohort effect on the rate of body development. This variability was partly explained by climatic conditions during late gestation. When fewer than 5 days with rainfall over 5 mm occurred in April, fawns were heavier. High temperatures during April and during the winter could also be involved in fast body development of roe deer fawns. Sex of fawn did not affect roe deer growth pattern. This was expected on the basis of low sexual dimorphism in size and low polygyny level characteristic of roe deer. Lastly, the date of birth did not affect the body development of roe deer fawns. High constancy of mean birth dates and high synchrony of births observed in this population could account for this result.     

Prior intrauterine position influences body weight in male and female mice

In two longitudinal studies, intrauterine location of male and female Rockland-Swiss mice relative to fetuses of the same and opposite sex dramatically influenced body weight. In one study, body weight of males and females that were located in utero between two female fetuses (OM animals) or between two male fetuses (2M animals) was assessed from birth to the time of weaning (25 days of age). The body weights of 2M females were indistinguishable from those of OM and 2M males on all but a few of the 25 postnatal days of life. Also, 2M females were significantly heavier than OM females from Postnatal Day 6 onward, and 2M males weighed significantly more than OM males from Postnatal Day 19 onward. In a second study, food intake and body weight of animals from different intrauterine locations were examined from 25 to 120 days of age. Regardless of prior intrauterine position, males were always heavier than females. However, prior in utero location modulated body weight in that 2M females were significantly heavier than OM females and 2M males were reliably heavier than OM males. Intrauterine position effects were observed in the absence of any appreciable influence of this variable on levels of food intake. Taken together, the results suggest that prior in utero location may influence metabolic set points involved in the regulation of body weight and fat storage.     

The biology of the Bush rat, Aethomys hindei Thomas in Southern Uganda

Studies were made on the Bush rat, Aethomys hindei in Lunyo forest (0° 5', 32° E) on the Northern shores of Lake Victoria. Rats were trapped daily (Monday-Saturday) for 47 weeks during November 1970 to November 1972 from 20–49 live traps set in a 40 by 100 m grid. In the laboratory they were examined for the condition of the external genitalia and for signs of pregnancy. Some pregnant rats were kept in the laboratory and their progeny measured at weekly intervals. The rate of growth (weight gain in g per day) was determined for both laboratory and field rats. Growth curves of laboratory rats were used to calculate the ages of young (<100 g) field rats, even though the results showed that at between 50 to 100 g field rats grew faster than laboratory rats and between 100 to 150 g, laboratory rats grew faster than field rats.
The weight distribution of rats in the field showed a clear weight difference between males and females; with some males weighing as much as 171 g while the maximum weight recorded for females was only 146 g. The weights obtained extend the weight range of these rats beyond that previously published.
Breeding (pregnancies) in the field occurred mostly in the wetter months of November- December and April whereas young animals occurred more in the drier months of December and January. Births obtained by calculation from laboratory growth curves occurred more in November.
Seasonality in the intensity of breeding was indicated although monthly breeding throughout the year was observed. The months of highest population densities were December, January and April.     

Control of ovarian follicular growth and maturation by the corpus luteum and the placenta during pregnancy in sheep

Ovarian follicular growth and maturation and its control throughout pregnancy have not been described fully in sheep. Experiment 1 characterized the size and maturation (steroid production in vitro and aromatase activity) of ovarian follicles obtained at days 20, 50, 80 and 110 of pregnancy compared with those obtained at day 12 of the oestrous cycle. There was no difference in the number of small follicles (< 3 mm in diameter) between cyclic and pregnant ewes, regardless of the stage of pregnancy. There was a marked reduction (P < 0.01) in the number of medium follicles (3-5 mm) starting at day 80 of pregnancy. Large follicles (> 5 mm) were not detected at day 110 of pregnancy. In vitro testosterone output by follicles was constant throughout pregnancy. Oestradiol output remained steady until day 80, but decreased markedly at day 110 of pregnancy. This decrease was associated with a reduction in aromatase activity in follicles obtained at this stage. Experiment 2 examined the effect of administration of high concentrations of progesterone between day 100 and day 120 after mating on resumption of follicular growth in ewes that underwent Caesarean section at day 99 of pregnancy. In ewes that underwent Caesarean section, progesterone supplementation was successful in mimicking the profile found in pregnant ewes, but did not prevent re-initiation of follicular growth, as demonstrated by the presence of large follicles (> 5 mm) at day 120 after mating. Experiment 3 examined the effects of PGF(2alpha)-induced regression of the corpus luteum of day 100 of pregnancy on resumption of follicular growth. High concentrations of PGF(2alpha) (0.28 mg kg(-1) body weight) administrated at day 100 of pregnancy were required to initiate regression of the corpus luteum. At day 120 after mating, the mean (+/- SEM) diameter of the largest follicle in PGF(2alpha)-treated ewes (3.40 +/- 0.47 mm) was significantly greater (P < 0.05) than that in control pregnant ewes (2.52 +/- 0.34 mm). Experiment 4 examined the effect of removal of the fetus and of the corpus luteum at day 100 of pregnancy on resumption of ovulation. Removal of the corpus luteum by PGF(2alpha) treatment at the time of removal of the fetus resulted in earlier occurrence of short luteal phases (27.8 versus 40.6 days, PGF(2alpha)-treated versus non-treated) but did not alter the timing of the first normal luteal phases (41 days). In conclusion, the results from these experiments indicate that placental compounds play a major role in inhibiting follicular growth and maturation during late pregnancy in sheep.     

Pregnancy of adult caribou (Rangifer tarandus): evidence for lactational infertility

To examine the relations between pregnancy, body condition, and lactation, 106 adult female caribou Rangifer tarandus granti ) of the Porcupine Herd were captured, weighed, measured, and scored for body condition in November 1990–1992. Blood samples were drawn for determination of pregnancy, and body fat content (kg) was estimated from the product of body weight and the body-condition score. Pregnant females were significantly fatter and heavier than non-pregnant females, and non- lactating females were significantly fatter, but no heavier, than lactating caribou. Probability of pregnancy was positively correlated with body weight and fat content, but prediction of pregnancy was improved when multiple independent variables, including skeletal dimensions and lactation status, were included in logistic models. Non-lactating females were more fertile than lactating females at a particular body weight and metatarsus length; but, at the same fatness, they were not more fertile than females that had lactated through the summer and were ceasing lactation in November. However, females that were extending lactation in November were least fertile, and this reduction of fertility was not explained by differences in body condition or skeletal dimensions. We suggest that the extended lactation group is exhibiting lactational infertility. Finally, unexplained differences in the relation between pregnancy rate and body condition exist among years, suggesting that interannual patterns in the nutrition and ecology of caribou affect the physiological relation between pregnancy and body condition.     

Diarrheal diseases and growth retardation in preschool Guatemalan children.

The relationship between diarrheal diseases and growth increments in total body length and weight was investigated in 716 rural Ladino Gautemalan children. Data on diarrheal diseases were provided by the mothers through retrospective surveys carried out at 14-day intervals. Increments in length and weight, semestral from near birth at four years and yearly thence to seven, were related to days ill with diarrheal diseases during the same time interval. Because the data here reported were collected over a two year period, a child may have had information for more than one period. In total, 1,343 child periods were investigated. Days ill with diarrheal diseases were found to be significantly associated with reduced growth in length and weight. It was assumed that the average differences in growth by seven years of age between children in the present sample and children from well-to-do societies, are mainly a function of environmental differences and consequently, a measure of the extent of growth retardation. By expressing the growth retardation specifically associated with diarrheal diseases as a fraction of the above differences it was then estimated that around 10% of this growth retardation was associated with diarrheal diseases.