Persistence of hormonal and metabolic rhythms during fasting in 7- to 9-day-old rabbits entrained by nursing during the night

Rabbit does nurse their litter once every 24 h during the night. We hypothesized that corticosterone, ghrelin, leptin, and metabolites such as glucose, liver glycogen, and free fatty acids could be affected in the pups by the time at which does nurse them. Therefore, we measured these parameters in pups nursed at 02:00 h (nighttime for the doe) to compare them with results from a previous study where does nursed at 10:00 h, during daytime. From postnatal day 7, pups were sacrificed either just before their scheduled time of nursing or at 4, 8, 12, 16, or 20 h after nursing (n = 6 at each time point); additional pups were sacrificed at 4 h intervals between 48 and 72 h after nursing to study the persistence of oscillations during fasting. All pups developed locomotor anticipatory activity to nursing. Corticosterone, ghrelin, and free fatty acids exhibited a rhythm that persisted in fasted pups. Glucose concentrations were lower in fasted than in nursed pups, and glycogen was only detected in nursed subjects. Leptin values were stable and low in nursed subjects but increased significantly in fasted subjects up to 72 h after the expected nursing time. The rhythm of ghrelin persisted during fasting, contrary to our previous findings in pups nursed during daytime (i.e., outside the natural time of nursing for this species). Therefore, in 7-day-old rabbit pups, night nursing is a strong zeitgeber for corticosterone, ghrelin, free fatty acids, and energy metabolites but not for leptin.     

Effect of nursing methods and faeces consumption on the development of the bacteroides, lactobacillus and coliform flora in the caecum of the newborn rabbits

The effect of nursing method and ingestion of maternal faeces on the development of the bacteroides, lactobacillus and coliform flora of the caecum in the first 10 days of life were examined in freely nursed pups having access to maternal faeces (Group FF), pups nursed once a day and having access (Group CF), or having no access (Group CN) to maternal faeces. Colonisation of the caecum by Bacteroides commenced already on day 3 after birth. On day 2 the bacteroides counts were below 100, while on day 4 they were already between 100 and 10,000. In Group CN, the Bacteroides counts were lower (by 14 to 40%) throughout the 10-day period studied than in the groups having access to maternal faeces. Differences between groups were significant only on days 4 and 6. The average number of maternal faecal pellets left behind the doe in Group CN was 3-4 (between 0.5 and 6.4 per doe). In Groups FF and CF the pellets became smaller, crumbled and finally disappeared from the nest box, they were consumed by the pups and could be found in their gastric content. The lactobacillus counts decreased in all three groups with age, from 6.0 to 3.5 log10 CFU.g-1 (FF), 4.6 to 2.8 log10 CFU.g-1 (CF) and 5.1 to 3.1 log10 CFU.g-1 (CN), respectively. The coliform counts were higher in the first 4 days in FF (5.6 log10 CFU.g-1) than in CF (< 2 log10 CFU.g-1) and CN (2-3.6 log10 CFU.g-1) animals. Bacteroides could be cultured from the surface of the vulvar labia (max. 1000 colony count) and the vagina (max. 190 colony count), so young rabbits could become "infected" by them already in the doe's vagina. Thus prevention of ingestion of maternal faeces only slightly influenced the development of the bacteroides flora, the faeces left behind by the doe did not play an exclusive role in their colonisation.     

Nursing behavior in dam-reared Russian saiga (Saiga tatarica tatarica) at the San Diego wild animal park

This study was designed to examine the nursing patterns and related behavior of young saiga raised by their dams. Four captive born lambs were observed at weekly intervals during continuous 14 h watches for the first 7 weeks of life. One-week-old lambs were found to nurse at an average rate of 1.1 bouts per hour and nursed for an average of 14.6 seconds per bout. This high nursing frequency and the average total daily nursing time of 242 seconds decreased rapidly with age. Saiga lambs sampled solid food as early as 4 days of age and were nearly dependent on solid food by the age of 7 weeks. Communal nursing, in which one or more lambs would nurse from an unrelated adult female while she nursed her own, was common. Grooming of the lamb by the dam was never seen except immediately following birth. © 1994 Wiley-Liss, Inc.     

Postnatal development and thermoregulation in the precocial European hare (<Emphasis Type="Italic">Lepus europaeus</Emphasis>)

We investigated postnatal development of captive juvenile European hares (Lepus europaeus) with respect to growth, food intake and thermoregulation. Leverets increased their body weight on average 8.5-fold within 35 days, with a peak in relative growth rate on day 8. Although leverets started to take up solid food in the 2nd week of lactation, milk was the main energy source. Leverets of larger litters (two or three young) had less energy supply via milk than those of smaller litters (one young), and digested more energy in form of solid food. Weaning weight was positively correlated with body weight at birth and decreased with increasing litter size. Metabolic rates were largely determined by ambient temperature (Ta) and the increasing body weights. Leverets were able to maintain normothermic body temperatures from the Ist day of life during cold exposure down to Ta -8 degrees C. In their 1st week of life leverets showed reduced rates of heat loss in the cold, possibly by using peripheral vasoconstriction. Our results suggest that the precocial development of leverets is characterised by high maintenance costs due to rapid growth and thermoregulation, which may lead to negative energy balances when food supply is inadequate and T(a)s are low. We hypothesise that these physiological characteristics have played an important role in the recent decline of European hare populations.     

Behaviour, population changes and dispersal of mountain hares (Lepus timidus) in Scotland

Mountain hares in north-east Scotland spent the day in forms in long heather and moved downhill in the evening to feed in hill pastures. Here they grazed intensively, often in groups of 4–6 individuals. In June and July adult females, then pregnant or lactating, grazed in daylight on the pastures. Leverets spent less time grazing, and more in play and exploration. They spent the day in cover near the feeding areas, and if disturbed during grazing crouched or went into cover, while adults fled. During 1982 and 1983 males predominated in groups of grazing hares, but in 1984 both sexes were equally represented. These changes in sex ratio were reflected in the increased proportion of females trapped for marking between February and late July during 1982–86. There was a dominance order related to weight among male hares and dominant hares approached more females. There was no firm evidence of mate-guarding. Males approached females regardless of their oestrous state and were usually rebuffed with varying degrees of intensity including striking and chasing. There were no interactions between females. Adults of both sexes chased leverets for short distances but leverets joined groups of feeding adults. Neither leverets nor first-winter hares showed evidence of dispersal. Mountain hares avoided sheep and cattle and there were fewer hares after the arrival of sheep in May.     

Differential Growth of Own and Alien Pups in Mixed Litters of Mice: A Role for Genomic Imprinting?

Female mice are said to be unable to distinguish own from alien offspring and will indiscriminately nurse each other's young in communal nests. Here, we present results of a split‐litter experiment that tested whether offspring growth was affected depending on whether they were nursed by their own or unrelated foster mothers. Pups of reciprocal crosses between C57/B6 and CBA/Ca strains were fostered in mixed litters that consisted half of their natural siblings and half of unrelated littermates of the reciprocal genotype. Analysing the relative growth of the two pup types showed that offspring gained proportionally more weight when nursed by their own mothers than their cross‐fostered litter mates during the period from day 15 until weaning, during which maternal provisioning effort contributes to pup weight gain. Before day 15 of the pups’ life, however, we found no advantage of being nursed by biological mothers, and we suggest that this may be due to the effects of paternally expressed genes in young that mask their maternal identity, thus favouring indiscriminate nursing of all young in a communal nest.     

Allonursing in captive belugas (Delphinapterus leucas)

This study describes allonursing (females nursing offspring that are not their own) in captive belugas (Delphinapterus leucas). In addition to the calf's mother, two females that were not pregnant or nursing at the time of the calf's birth spontaneously lactated and nursed the male calf intermittently throughout 34 months of his life at the Vancouver Aquarium Marine Science Center. These observations suggest that allonursing may also take place in their wild counterparts and add to existing evidence of alloparental care in this species. Alloparental care, the care of nonoffspring, has been observed in every major mammalian taxon; the protection of calves through alloparental care may be a strong evolutionary benefit. Zoo Biol 29:633–637, 2010. © 2010 Wiley‐Liss, Inc.     

Factors Affecting Developmental Increase of Tyrosine Aminotransferase in Rat Liver Immediately after Birth

Labeling with ³⁵S-methionine of dispersed hepatocytes prepared from neonatal rat liver and successive immunoprecipitation with antiserum against tyrosine aminotransferase (TAT) indicated that increase of TAT activity to a peak about 12 hours after birth and the decrease thereafter are mainly due to changes of TAT synthesis. Similar changes of TAT activity was also observed in the livers of premature neonates which were taken out by Caesarian section and nursed by foster mothers. This indicated that the appearance of TAT activity at this period is not an event programmed along with fetal development but is triggered by birth. The level of glucagon in neonatal plasma increased after birth. Administration of glucagon to neonates caused a great increase of TAT activity whereas the effect of dexamethasone was not so evident. These suggested that glucagon is an important factor affecting the abrupt appearance of TAT after birth.     

Food intake in captive leverets before weaning and the composition of the milk of the brown doe-hare (Lepus europaeus)

Daily milk and solid food intakes were studied in leverets before weaning and during 52 lactations in captive doe-hares. Changes in milk composition were studied in parallel during 11 other lactations. With the mode of feeding used (one nursing per 24 hr), milk and solid food intakes were recorded for the first 30 neonatal days. The profile of milk intake had three phases: it showed an increase between D0 and D12, a plateau between D12 and D22, and a decrease between D22 and D30. Solid food intake began at D7 and increased significantly from D14. The mean levels of dry matter, fat and protein in doe hare's milk were similar to those in rabbit's milk The amino acid composition of total protein resembled that of rabbit's milk. There were fewer medium-chain fatty acids (8:0-14:0) in here's milk than in rabbit's milk and the levels of some major minerals (Ca, P, K) were also different. The levels of protein and medium-chain fatty acids (except 14:0) increased significantly with time. On the other hand, the levels of long-chain fatty acids (except 18:0 and 18:3, N = 3) decreased significantly. There was no significant change in the other factors studied.     

Major role of suckling stimulation for inhibition of estrous behaviors in lactating rabbits: acute and chronic effects

Lactation in rabbits induces anestrus: sexual receptivity and scent-marking (chinning) are reduced despite the brevity of suckling (one daily nursing bout, lasting around 3 min). The mechanisms underlying this effect are unknown but, as chinning, lordosis, and ambulation in an open field are immediately inhibited by the peripheral stimulation received during mating we hypothesized that, across lactation, suckling stimulation would provoke a similar effect. To test this possibility we provided litters of 1, 3, 5, or 10 pups across lactation days 1-15 and quantified chinning and ambulation frequencies, the lordosis quotient, and milk output. Baseline chinning frequency, determined before the daily nursing bout, was low across lactation days 1-15 in does nursing 3, 5 or 10 pups but it increased steadily across days 1-10 in rabbits suckling one pup. Yet, a single young was sufficient to abolish chinning for about 1h, after which this behavior rose again. Suckling litters of all sizes reduced (but did not abolish) ambulation frequency, both chronically (baseline levels declined across days 1-5) and acutely. Sexual receptivity was significantly reduced on lactation day 15 only in does that had nursed 10 pups. Large litter size promoted a larger milk output and a normal duration of nursing episodes. Results support a major role of suckling stimulation for the suppression of estrous behaviors and ambulation through as yet unidentified mechanisms.     

自然哺乳长颈鹿的幼仔行为研究

对成都动物园2005年和2008年出生长颈鹿幼仔在母兽哺乳情况下的1月龄内幼仔行为进行了观察和分析.发现幼长颈鹿的主要行为有卧、走、站、吃奶、跑等,其中卧和站的行为分别占全天时间的61.7%和32.3%;幼长颈鹿在10 d左右开始学习采食青草,4周龄时明显能吃到一些青草.     

圈养大熊猫同时哺育双胞胎行为观察

2003 年,圈养大熊猫“梅梅”首例哺育成活一胎二仔,通过对其近半年的育幼行为观察,结果发现:1) 母兽主要以同时衔2 仔、同时衔和抱2 仔二种方式将幼仔抱入怀中哺育;60 d 内, 育幼姿势以坐位为主,倦卧其次, 其它姿势更少, 其中坐位随日龄增加逐渐减少, 倦卧变化不大。2) 母兽活动时间在产仔当天最多, 之后显著下降并维持在35.2 ± 0.6% 的低水平, 47 d 后再缓慢上升到108 d 后的54.8 ± 0.9% 。3) 双胞胎幼仔间哺乳的日均次数和时间无显著差异。4) 7 d 内2 幼仔“仔在母身上” 的时间占100%, 21 ～ 23 d 后显著减少, 而“母体盖仔”、“仔在母身边”和“母仔自然分离”的时间显著增加, 但“母体盖仔” 的时间在32 d 左右后又显著减少;双胞胎分别在与母兽的此四种位置变化的时间上无显著差异。5) 母兽的活动、幼仔哺乳日均次数、“母仔自然分离”在全天的日均时间分布有峰、谷变化。6) 随幼仔活动能力的逐渐增强,幼仔离“育幼窝”的距离也逐渐增加,双胞胎幼仔离“育幼窝”的远近也有差别。7)母兽分别与其雄性双胞胎幼仔玩耍的时间有显著差异,而两幼仔自玩的时间无差异,此两双胞胎自玩和一起玩耍所用时间远大于分别与母兽玩耍的时间。该研究丰富了大熊猫育幼行为内容,并为以后的大熊猫双胞胎育幼提供了可供参考的行为资料。     

The effect of lactating rabbit does on the development of the caecal microbial community in the pups they nurture

AIMS: To study the effect of microbial community of the rabbit does as influenced by dietary factors, on the development of the gut microbiota of their litters. METHODS AND RESULTS: Twenty-four lactating does were given a diet unsupplemented (NAB) or with 100 ppm of bacitracin (BAC) or tiamulin (TIA) to modify their digestive microbiota. Litters were adjusted to six pups. In Trial 1, four does per diet milked their own six pups. In Trial 2, two does per diet nursed three of their pups and three fostered from the doe given the same diet. In Trial 3, two does on each diet nursed three of their pups and three fostered from another doe fed on another diet. Denaturing gradient gel electrophoresis (DGGE) analyses of the litter microbiota showed that the effect of the milking mother was greater than the influence of the biological mother. TIA had a strong effect on the bacterial profile even prevailing over that of the milking mother, in contrast to BAC. CONCLUSIONS: Nursing mother microbiota plays an important role over that of the litter. Caecal colonization that occurs during the lactation process prevailed over that during the partum. SIGNIFICANCE AND IMPACT OF THE STUDY: Manipulation of the mother's microbiota may help for adaptation of the litter microbial community against pathologic digestive processes.     

Nursing behaviors of beluga calves (Delphinapterus leucas) born in captivity

The nursing behaviors of two beluga whale calves were observed for the first 55 days postpartum. For both calves, the total time spent nursing in a given period peaked around 7–10 days postpartum and then declined over time. One calf, however, was found to have an unusual decline in nursing at day 35 postpartum. Ten days later, this calf was diagnosed as having a bacterial infection and given antibiotics. This suggests that early detection of health problems may be possible by observing calves' nursing behavior. For both calves, their general nursing patterns were similar, although one calf consistently nursed more than the other. Both calves nursed roughly every half hour, neither showed any signs of a circadian pattern, and carryover effects for both calves were found, indicating that there was a relationship in the overall nursing pattern from one interval to the next. That is, if nursing dropped off during one interval, it was typically made up in the next interval. Zoo Biol 16:247–262, 1997. © 1997 Wiley-Liss, Inc.     

Sociality, time and space in a sparse population of rabbits (Oryctolagus cuniculus)

This 10-year study describes a sparse population of rabbits ( Oryctolagus cuniculus ) living in small, semi-isolated groups on river flats with some scrub in an otherwise forested valley. The rabbits lived above ground in the scrub by day and fed in the open at night. They bred in isolated 'stops' dug in the shingle often far from suitable grazing for the young. Many stops collapsed, killing the young. Home ranges were recorded by radio telemetry. Bucks had larger ranges than does and spent less time in the scrub. Adults of both sexes were sedentary for life. Some bucks travelled > 500 m at night. Most ranges were too large to be defended strictly; night feeding grounds were often communal. In the evening, adult rabbits spent 44% of the time feeding and 33% inactive. Social interactions were frequent. At all seasons, in the evening most adult rabbits were seen singly or as pairs. Pairs seldom remained intact for > 12 months even when both partners were alive. The buck of the pair was usually older than the doe because bucks outlived does. The adult survival rate was about 0.80 for bucks, 0.55 for does. Four bucks lived for > 7 years. Few young survived for long after leaving the nest; many were killed by predators. Dungheaps, used for 60% of the droppings, were concentrated near the scrub where rabbits congregated in the evening. The behaviour of these rabbits differed in many ways from that of rabbits in enclosures or at higher density in the wild.     

Endogenous clock gene expression in the suprachiasmatic nuclei of previsual newborn rabbits is entrained by nursing

The rabbit is particularly suitable for investigating the development of mammalian circadian function. Blind at birth, the pups are only visited by the mother to be nursed once every 24 h for about 3 min and so can be studied largely without maternal interference. They anticipate the mother's visit with increased behavioral arousal and with a rise in body temperature, both of which represent endogenous circadian rhythms. We now report that in newborn pups the suprachiasmatic nuclei of the hypothalamus (SCN; the main circadian pacemaker in mammals) show endogenous 24‐h rhythmicity in the expression of the clock genes Per1, Per2, and Bmal1. Pups nursed from postnatal days 1 to 7 and fasted to day 9 showed the same rhythms of clock gene expression as normally nursed controls. We also report that these rhythms are entrained by nursing. Pups killed on postnatal days 3–4 showed the same rhythms in gene expression as pups in the previous experiment, whereas littermates subsequently nursed from postnatal days 4 to 7 with nursing delayed 6 h showed a corresponding shift in the diurnal pattern of clock gene expression. Consistent with this, two groups of pups implanted with telemetric thermal sensors and nursed 6 h apart had daily patterns in body temperature synchronized with the two different nursing times. We conclude that the expression of clock genes associated with the newborn rabbit's circadian system is entrained by nonphotic cues accompanying nursing, the exact nature of which now needs to be clarified. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2009     

Nonsurgical collection of blastocysts from dairy goats

In two trials, eight attempts were made to collect fertilized ova from dairy goats by nonsurgical methods. In both trials the cervix of each doe was dilated by inserting a Laminaria japonica tent device into the cervical canal prior to flushing. In Trial 1, an attempt was made to collect embryos from four nonsuperovulated does by flushing phosphate-buffered saline (PBS) through a rigid pipette. Little fluid and no embryos were recovered from the does. All four donors were in estrus two days after the procedure. In the second trial, FSH-superovulated does were collected on day 5 following estrus. The donors were anesthetized, and a modified Foley catheter was passed through the cervical canal. In three does, a 24 ga. two-way Foley was stiffened with a size 10 (French) polypropylene catheter which penetrated the Foley, extending 7 cm beyond the tip. Recovery of flushing medium with this device was minimal, and laparotomy of one doe revealed a punctured uterus. Replacement of this device with a different catheter, through which a polypropylene catheter (size 5 Fr.) penetrated only 1 to 2 cm, resulted in satisfactory return of infused PBS, and recovery of two blastocysts and one degenerated ovum from this doe. Use of the same device on a second doe without laparotomy resulted in collection of seven blastocysts and three degenerated ova. Of three observed donors that received Laminaria tents (including one which was not flushed) two were in estrus three days after the procedure, while unused synchronized recipients showed normal cycle lengths. Surgical transfer of two blastocysts from each donor to each of two synchronized recipients resulted in the birth of twin kids from one recipient doe. The study demonstrates the feasibility of embryo collection from dairy goats by nonsurgical means.     

Activation of Organum Vasculosum of Lamina Terminalis,Median Preoptic Nucleus,and Medial Preoptic Area in Anticipation of Nursing in Rabbit Pups

Rhythmic feeding in rabbit pups is a natural model to study food entrainment because, similar to rodents under a schedule of food restriction, these animals show food-anticipatory activity (FAA) prior to daily nursing. In rodents, several brain systems, including the orexinergic system, shift their activity to the restricted feeding schedule, and remain active when subjects are hungry. As the lamina terminalis and regions of the preoptic area participate in the control of behavioral arousal, it was hypothesized that these brain regions are also activated during FAA. Thus, the effects of daily milk ingestion on FOS protein expression in the organum vasculosum of lamina terminalis (OVLT), median preoptic nucleus (MnPO), and medial preoptic area (MPOA) were examined using immunohistochemistry before and after scheduled time of nursing in nursed and fasted subjects. Additionally, FOS expression was explored in orexin (ORX) cells in the lateral hypothalamic area and in the supraoptic nucleus (SON) because of their involvement in arousal and fluid ingestion, respectively. Pups were entrained by daily nursing, as indicated by a significant increase in locomotor behavior before scheduled time of nursing in both nursed and fasted subjects. FOS was significantly higher in the OVLT, MnPO, and MPOA at the time of nursing, and decreased 8?h later in nursed pups. In fasted subjects, this effect persisted in the OVLT, whereas in the MnPO and MPOA, values did not drop at 8?h later, but remained at the same level or higher than those at the time of scheduled nursing. In addition, FOS was significantly higher in ORX cells during FAA in nursed pups in comparison with 8?h later, but in fasted subjects it remained high during most fasting time points. Additionally, OVLT, SON, and ORX cells were activated 1.5?h after nursing. We conclude that the OVLT, MnPO, and MPOA, but not SON, may participate in FAA, as they show activation before suckling of periodic milk ingestion, and that sustained activation of the OVLT, MnPO, and MPOA by fasting may contribute to the high arousal state associated with food deprivation. In agreement with this, ORX cells also remain active after expected nursing, which is consistent with reports in other species.     

Circadian rhythm of the mitotic activity of pulmonary interalveolar septum cells in rats of different ages]

The daily rhythm of mitotic activity in the lungs of the 20-day-dd embryo coincides with the rhythm of the adult organism. The mitotic activity of the 1-, 3- and 10-day-old animals was the maximum in the evening and the minimum-in the morning hours. A definitive rhythm of cells division (with the maximal mitotic activity in the morning and the minimal-in the evening) is established beginning from the 17th day of the postnatal development. The average mitotic activity is very high in the embryos, but it falls immediately after birth. It rises on the 3rd day, and begins to decrease again from the 7th day after birth.     

Spontaneous dermatophilosis in twin white-tailed deer fawns.

Twin white-tailed deer (Odocoileus virginianus) fawns captured in Morris County, New Jersey, displayed papular, darkly pigmented scabs principally on the skin overlying the nasal bones, dentary, commissure of the lips and ears. Histopathological and bacterial examinations revealed Dermatophilus congolensis. The epidermitis caused by this bacterium apparently had developed within the first 12 to 14 days after birth and had begun to regress by one month of age. The location of the lesions suggested transmission during nursing from an infected doe. This is believed to be the first confirmed report of this zoonotic disease in white-tailed deer, with isolation of the etiologic agent, outside the State of New York. Epizootiological considerations are discussed.