Suckling, Feeding, and Swallowing: Behaviors, Circuits, and Targets for Neurodevelopmental Pathology.

All mammals must suckle and swallow at birth, and subsequently chew and swallow solid foods, for optimal growth and health. These initially innate behaviors depend critically upon coordinated development of the mouth, tongue, pharynx, and larynx as well as the cranial nerves that control these structures. Disrupted suckling, feeding, and swallowing from birth onward-perinatal dysphagia-is often associated with several neurodevelopmental disorders that subsequently alter complex behaviors. Apparently, a broad range of neurodevelopmental pathologic mechanisms also target oropharyngeal and cranial nerve differentiation. These aberrant mechanisms, including altered patterning, progenitor specification, and neurite growth, prefigure dysphagia and may then compromise circuits for additional behavioral capacities. Thus, perinatal dysphagia may be an early indicator of disrupted genetic and developmental programs that compromise neural circuits and yield a broad range of behavioral deficits in neurodevelopmental disorders.

Nighttime Suckling Behavior in Captive Giraffe (Giraffa camelopardalis reticulata).

Suckling behaviors are useful to better understand mother-offspring relationships. However, in many species, knowledge about nighttime suckling behavior is sparse. In the present study, we investigated suckling behavior in four calves of the reticulated giraffe (Giraffa camelopardalis reticulata) and their mother in the Kyoto City Zoo, Japan, by analyzing video clips of 9614 h. The relation between a calf's age and the mean duration and frequency of suckling were consistent with the results of previous daytime studies: the longest duration (80 ± 4 s) and highest frequency (0.41/h) of suckling occurred when the calves were young, and decreased thereafter. Suckling frequency was lower at night than during the day, probably because the mother spent much of the time resting at night. The mother initiated suckling behavior in offspring until six months of age. Most often, the mother terminated suckling except during the first few weeks after birth. Additionally, we reported that the average weaning period was 448 days (n = 5) and that the last born (sixth) continued to suckle for more than 750 days, which is a rare phenomenon. We believe the present report helps to fill the lack of knowledge about nighttime suckling behavior in giraffe.

Effects of maternal 25-hydroxycholecalciferol during the last week of gestation and lactation on serum parameters, intestinal morphology and microbiota in suckling piglets.

This study was conducted to test the effects of maternal 25-hydroxycholecalciferol (25OHD3) supplementation on serum parameters, intestinal morphology and microbiota in suckling piglets. The experiment started on day 107 of gestation and lasted until piglets were weaned on day 21 of lactation. Thirty-two sows were allocated randomly to two treatments (ND diet, basal diet with 2000 IU/kg of vitamin D3; 25-D diet, basal diet with 50 µg/kg 25OHD3). Results showed that maternal 25-D treatment increased (p < 0.05) serum 25OHD3 concentration in the umbilical cords, which led to higher (p < 0.05) serum 25OHD3 concentration of suckling piglets from 25-D sows. The GSH-Px activity in colostrum was higher (p < 0.05), as well as SOD and GSH-Px activities in milk, were higher (p < 0.05) in 25-D sows than ND sows. Compared with piglets suckling ND sows, piglets suckling 25-D sows had higher (p < 0.05) serum SOD activity on day 7, 14 and 21 of lactation. On day 21 of lactation, piglets form 25-D sows had greater (p < 0.05) serum levels of GH and IGF-I and lower (p < 0.05) serum DAO activity than those from ND sows. Piglets from 25-D sows had higher (p < 0.05) jejunal villus height than those from ND sows. Feeding 25OHD3 to sows tended to increase (p < 0.10) the species richness in the colonic digesta of suckling piglets, as reflected by the α-diversity index of Chao-1. In the caecal digesta, the α-diversity for bacterial community analysis of Simpson and Shannon was lower (p < 0.05) in 25-D piglets than ND piglets. The relative abundances of colonic Alloprevotella and caecal Lactobacillus were significantly higher, while the population of caecal [Eubacterium]_coprostanoligenes_group was lower (p < 0.05) in 25-D piglets than ND piglets. In conclusion, maternal 25OHD3 supplementation partly improved antioxidant status in sows and suckling piglets and altered gut microbiota in the hindgut of piglets.

The effects of feed naturally contaminated with Fusarium mycotoxins on the thymus in suckling piglets.

In this study, feed naturally containing Fusarium mycotoxins was fed to gilts during the perinatal period, and the effects on the thymus were investigated in one-week-old piglets. Twenty gilts were divided into equal control (0.26 mg deoxynivalenol, DON) and experimental (5.08 mg DON, 0.09 mg zearalenone and 21.61 mg fusaric acid per kg of feed) groups. One suckling piglet from each litter (n = 20) was sacrificed at one week of age to obtain thymus samples for further analysis. The cortex to medulla ratio of the thymus was morphometrically analysed using NIS Elements BR (Nikon) software. Paraffin-embedded thymus sections were stained to quantify apoptosis (with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling - TUNEL method), cellular proliferation (Ki-67) and macrophages (MAC 387). The results showed that the thymus cortex (P = 0.023) to medulla (P = 0.023) ratio was significantly lower in the experimental group. The number of apoptotic cells (cortex, P = 0.010, medulla, P = 0.001) and the number of proliferating cells in the thymus cortex (P = 0.001) and medulla (P < 0.001) were significantly higher in the experimental group. Our results indicate that feeding Fusarium mycotoxins to a parent animal during the perinatal period induces significant alterations in the thymus of one-week-old piglets, which indicates an immunosuppressive effect in piglets.

Impact of a high-protein diet during lactation on milk composition and offspring in a pig model.

PURPOSE: Early postnatal nutrition not only holds relevance to infant growth, but also determines the risk of developing obesity and chronic diseases such as diabetes type 2 and cardiovascular diseases in adulthood. It is suggested that a high-protein (HP) diet in early childhood can predispose children to obesity. However, data concerning possible alterations in milk composition and the development of the offspring in response to a maternal HP diet are currently not available. To address this question, we conducted a study using pigs as a model organism. METHODS: At parturition, sows were assigned to two experimental groups. During lactation, the control group received a diet with a protein content of 16%, whereas the diet of the HP group contained 30% protein. After 28 days of lactation, samples were taken from sows and piglets for the quantification of free amino acids and other metabolites and for histology. RESULTS: Serum and milk urea showed the most marked differences between the two groups of sows, whereas serum urea concentration in piglets did not differ. Here, we found that the intake of an HP diet changed a series of metabolites in sows, but had only small effects on milk composition and virtually no effects on growth in the offspring. Interestingly, maternal protein intake during lactation shapes the microbiome of the offspring. CONCLUSION: From our current study, we conclude that even a very high maternal protein intake throughout lactation has no impact on growth and health parameters of the offspring.

Alfalfa hay improves nursing performance of Awassi ewes and performance of growing lambs when used as a source of forage compared with wheat straw.

Two experiments were conducted to evaluate the effect of replacing wheat straw (WS) with alfalfa hay (ALF) in diets fed to Awassi lactating ewes (exp. 1) and weaned lambs (exp. 2). In each experiment, sheep were fed 1 of 3 treatment diets containing WS only, WS and ALF mix (50:50; WS-ALF), or ALF only as the forage sources. In exp. 1, 33 lactating Awassi ewes were assigned randomly to treatment diets (11 ewes/diet) and fed ad libitum for 56 days. Intakes of dry matter (DM) and crude protein (CP) were greater (P = 0.001) in WS-ALF and ALF diets than WS diet. Ewe weight-of-lamb weaned, and nursing-lamb average daily gain (ADG) was greatest for ALF, intermediate for WS-ALF, and least for WS treatment groups (P < 0.0001). Milk production (kg/day) tended to be greater (P = 0.07) in ALF diets compared with WS diets. Milk protein, total solids, and lactose production (g/day) were greater (P < 0.04) in ewes fed ALF and WS-ALF diets compared with WS diet. In exp. 2, 27 newly weaned lambs were randomly assigned to treatment diets (9 lambs/treatment) and fed ad libitum for 70 days. Intake and digestibility of DM were greater (P < 0.05) in lambs fed the ALF diet compared with the WS diet. Lamb total gain and ADG were greater (P < 0.01) for lambs fed WS-ALF and ALF diets compared with WS diet. Replacement of wheat straw with alfalfa hay improved most of performance and productivity measured variables of Awassi lactating ewes and growing lambs.

Effects of maternal artificial vocalization on hyperprolific lactating sows and piglets behavior.

The objective of this trial was to evaluate the behavioral patterns and performance of lactating sows and their litters under the effect of artificial vocalization. Twenty-eight sows and their litters were distributed in a completely randomized design in a 2x2 factorial scheme (artificial vocalization x lactation week). The behavior of the animals was monitored during 24 hours on the 7th and 15th days of lactation, analyzing the number, interval, and frequency of nursings. The body condition and performance of the sows were also evaluated. Artificial vocalization promoted higher frequencies of eating for sow and nursing for piglets (P <0.05), increased inactive sow behavior (P <0.05), and reduced sow alert in activity (P <0.05). The number and duration of suckling sessions at the 15thday of lactation were reduced (P <0.05). The use of artificial vocalization did not affect the body condition or milk production of the lactating sows, or the performance of the litter during lactation (P> 0.05). The use of maternal artificial vocalization during lactation of sows promoted greater lactation efficiency and longer rest time, favoring the sows' welfare.

A novel fecal stable isotope approach to determine the timing of age-related feeding transitions in wild infant chimpanzees.

OBJECTIVES: Determining nutritional development in wild primates is difficult through observations because confirming dietary intake is challenging. Physiological measures are needed to determine the relative contributions of maternal milk and other foods at different ages, and time of weaning. We used fecal stable carbon and nitrogen isotopes (δ13 C, δ15 N) and fecal nitrogen concentrations (%N) from wild chimpanzees at Ngogo, Uganda, to derive physiological dietary indicators during the transition from total reliance on maternal milk to adult foods after weaning. MATERIALS AND METHODS: We analyzed 560 fecal samples collected non-invasively from 48 infants, their mothers, and 6 juvenile siblings. Most infant and juvenile samples (90%) were matched to samples collected from mothers on the same day. Isotopic assessments were compared with observations of nursing and feeding. RESULTS: Infants ≤1 year old showed average δ15 N, δ13 C and %N ratios that were 2.0‰, 0.8‰ and 1.3% greater than their mothers, respectively, interpreted as trophic level effects. Although data collected on newborns were few, results suggest that solid foods were consumed within 2-5 months after birth. Trophic level differences decreased steadily after 1 year, which indicates a decreasing relative contribution of milk to the diet. Isotopic results indicated infants were weaned by 4.5 years old-more than a year earlier than observations of nipple contacts ceased, which revealed the occurrence of "comfort nursing." Juvenile isotopic signatures indicate no nursing overlap between siblings. DISCUSSION: Our results resemble the stable isotope differences of human babies. This study contributes to a model of chimpanzee nutritional development required to understand early life history patterns in hominins.

Developmental changes in feeding behaviors of infant chimpanzees at Mahale, Tanzania: Implications for nutritional independence long before cessation of nipple contact.

OBJECTIVES: Weaning of chimpanzees is considered to occur at 4-5-years-old with complete cessation of nipple contact and timing of reconception calculated by inter-birth interval minus gestation length. This is also the basis of "early weaning" in humans (i.e., approximately 2.5-years-old). However, recent studies of the survival of orphans and the first molar (M1) eruption in wild chimpanzees have predicted that infants move toward nutritional independence at 3-years-old. Therefore, this study aimed to investigate ontogeny of feeding behavior at around 3-years-old in wild infant chimpanzees. MATERIALS AND METHODS: I studied 19 infants aged 1-60 months in the M group in Mahale Mountains National Park, Tanzania. The total observation time was 518 h, 25 min. RESULTS: At around 3-years-old, infant chimpanzees spent more total feeding time, and time feeding on leaves, and food physically difficult to process without food transfer from other individuals. These results suggest that infant chimpanzees significantly reduced their dependence on milk for nutrition at around 3-years-old, that is, before cessation of nipple contact. DISCUSSION: This study suggests that M1 eruption in wild Eastern Chimpanzees is an index of the period when infants move toward nutritional independence with a key dietary transition. This is the first study to provide behavioral evidence of the large temporal gap between nutritional independence of infants and reconception of mothers in great apes, and clarify the unique feature of human life history whereby mothers can reconceive before an infant reaches nutritional independence.

Maternal dietary linoleic acid supplementation promotes muscle fibre type transformation in suckling piglets.

As meat quality is basically dependent on muscle fibre characteristics, it is important to know how muscle fibres are regulated and transformed. This study aimed to investigate the effect of maternal dietary supplementation on muscle fibre types using 3% saturated fatty acid (palmitic acid, PA) or 3% unsaturated fatty acid (linoleic acid, LA) from 80 days of gestation to the weaning of offspring (25 days post-natal). The results indicated that higher mRNA levels of MyHCI type genes were found in the soleus muscles of piglets that suckled from LA-supplemented sows than from PA-supplemented sows. In addition, LA treatment increased the gene expression of the type I muscle fibre marker troponin I (p < 0.01), suggesting that LA promoted muscle fibre type transformation to type I fibres. Moreover, PGC-1α (p < 0.01) and MEF2c (p < 0.05) mRNA levels were higher in the piglets from the LA treatment group than in those from the PA treatment group. Furthermore, LA supplementation also significantly increased AMP-activated protein kinase (AMPK) mRNA levels (p < 0.05), which is an upstream regulator of PGC-1α. Collectively, these findings demonstrated that maternal dietary LA supplementation promoted muscle fibre transformation to type I fibre and that this process may be mediated through an AMPK-dependent pathway.

Evaluation of different dose rate combinations of ketamine, romifidine and azaperone for castration of 3-4 and 5-6 weeks old piglets.

INTRODUCTION: In this study dose rate combinations of ketamine, azaperone and romifidine were tested in 3-4 (G3-4) and 5-6 weeks (G5-6) old piglets according to a dose rate decision tree (DRT) to provide calm anaesthesia induction, reaction-free anaesthesia for castration and smooth recovery within 2 hours. When a combination failed to meet those criteria in 2 piglets, the next dosage of the DRT was tested. In G3-4 four combinations were tested in 14 piglets with dose rates of 10-20 mg/kg ketamine, 3 mg/kg azaperone and 0.15-0.20 mg/kg romifidine IM. Induction was smooth in all piglets, but depth of anaesthesia or recovery (11 and 6 piglets) were insufficient. In G5-6 five combinations were tested in 37 piglets with dose rates of 10-20 mg/kg ketamine, 3-4 mg/kg azaperone and 0.15-0.20 mg/kg romifidine IM. Induction was smooth in all piglets but 2. Depth of anaesthesia or recovery (17 and 7 piglets, respectively) were insufficient. In the present study with 3-4 and 5-6 weeks old piglets, acceptable quality of anaesthesia could not be achieved despite using high drug dose rates.

INTRODUCTION: Des combinaisons de doses de kétamine, azapérone et romifidine ont été testées sur la base d'un arbre de décision de dose afin de définir la dose qui assurait, chez des porcelets de 3-4 (G3-4) et de 5-6 (G5-6) semaines une induction tranquille, une anesthésie sans réaction lors de la castration et une phase de réveil calme, terminée en deux heures. Lorsqu'une combinaison de ces critères n'était pas obtenue chez 2 porcelets, on passait à la dose suivante proposée par l'arbre de décision. Dans le G3-4, 4 combinaisons avec des doses de 10-20 mg/kg de kétamine, 3 mg/kg d'azapérone et 0.15-0.20 mg/kg de romifidine IM ont été testées chez 14 porcelets. L'induction était calme chez tous les porcelets mais la profondeur de l'anesthésie ou la phase de réveil étaient insuffisantes chez 11 respectivement 6 porcelets. Dans le G5-6, 5 combinaisons avec des doses de 10-20 mg/kg de kétamine, 3-4 mg/kg d'azapérone et 0.15-0.20 mg/kg de romifidine IM ont été testées chez 37 porcelets. L'induction était calme à deux exceptions près mais la profondeur de l'anesthésie ou la phase de réveil étaient insuffisantes chez 17 respectivement 7 porcelets. Lors de la présente étude, il n'a pas été possible, malgré l'utilisation de doses élevées, d'obtenir chez des porcelets de 3-4 respectivement de 5-6 semaines une qualité d'anesthésie acceptable.

Creep feeding effects on male Nellore calves influencing behavior and performance of their dams.

The objective of the present study was to evaluate the effect of different schemes of calves' supplementation in a creep feeding system, on the behavior of Bos indicus calves and dams, and also the influence of the calves' supplementation on dams' performance. Forty-eight Nellore male calves (147 ± 7 kg body weight and 3 months of age) in the suckling phase and their dams (476 ± 9 kg and 6 years of age) were studied in a completely randomized design. The experiment was divided into two periods of 71 days. The treatments were 5- and 10-g supplement dry matter (DM)/kg BW day offered in periods 1 and 2, respectively (5S/10S); 10- and 5-g supplement DM/kg BW day offered in periods 1 and 2, respectively (10S/5S); 7.5-g supplement DM/kg BW day in both periods 1 and 2 (7.5S); and mineral mix ad libitum in both periods 1 and 2 (MM). No differences (P < 0.05) in body condition score (BCS), final body weight (FBW), and average daily gain (ADG) were found in dams' performance. Calves from MM treatment spent more time (P < 0.05) grazing than the supplemented calves from 5S/10S and 10S/5S treatments, in the first period. No difference in suckling time was found between the treatments (P > 0.05) in the first evaluated period. Calves from 10S/5S treatment spent more time suckling and less time eating supplements (P < 0.05) than 5S/10S treatment animals, in the second evaluated period. Dams of MM treatment's calves had more idle time and lower grazing time when compared with the mothers of calves from 5S/10S and 10S/5S treatments. It was concluded that different schedules of Nellore calves' supplementation on pasture do not affect their mothers' performance, and supplementation decreases the grazing time of calves in the suckling phase.

Mothers and offspring: The rabbit as a model system in the study of mammalian maternal behavior and sibling interactions.

UNLABELLED: This article is part of a Special Issue "Parental Care". Jay Rosenblatt effectively promoted research on rabbit maternal behavior through his interaction with colleagues in Mexico. Here we review the activities of pregnant and lactating rabbits (Oryctolagus cuniculus), their neuro-hormonal regulation, and the synchronization of behavior between mother and kits. Changing concentrations of estradiol, progesterone, and prolactin throughout gestation regulate nest-building (digging, straw-carrying, fur-pulling) and prime the mother's brain to respond to the newborn. Nursing is the only mother-young contact throughout lactation. It happens once/day, inside the nest, with ca. 24h periodicity, and lasts around 3min. Periodicity and duration of nursing depend on a threshold of suckling as procedures reducing the amount of nipple stimulation interfere with the temporal aspects of nursing, though not with the doe's maternal motivation. Synchronization between mother and kits, critical for nursing, relies on: a) the production of pheromonal cues which guide the young to the mother's nipples for suckling; b) an endogenous circadian rhythm of anticipatory activity in the young, present since birth. Milk intake entrains the kits' locomotor behavior, corticosterone secretion, and the activity of several brain structures. Sibling interactions within the huddle, largely determined by body mass at birth, are important for: a) maintaining body temperature; b) ensuring normal neuromotor and social development. Suckling maintains nursing behavior past the period of abundant milk production but abrupt and efficient weaning occurs in concurrently pregnant-lactating does by unknown factors. CONCLUSION: female rabbits have evolved a reproductive strategy largely dissociating maternal care from maternal presence, whose multifactorial regulation warrants future investigations.

Does supplementation of beef calves by creep feeding systems influence milk production and body condition of the dams?

The aim of this study was to evaluate the effects of beef calves' supplementation in creep feeding systems on milk yield, body weight (BW), and body condition score (BCS) of their dams on tropical pastures using a meta-analytical approach. The database was obtained from 11 experiments conducted between 2009 and 2014 in Brazil, totaling 485 observations (cows). The database consisted of 273 Nellore and 212 crossbred (7/8 Nellore × 1/8 Holstein) cows. All experiments were carried out in the suckling phase (from 3 to 8 months of age of calves) during the transition phase between rainy and dry seasons from February to June of different years. The data were analyzed by a meta-analytical approach using mixed models and taking into account random variation among experiments. Calves' supplementation (P ≥ 0.59) and the calves' sex (P ≥ 0.48) did not affect milk yield of cows. The average fat-corrected milk (FCM) yield was 6.71 and 6.83 kg/day for cows that had their calves supplemented and not supplemented, respectively. Differences were observed (P < 0.0001) for milk yield due to the genetic group where crossbred cows presented greater FCM yield (7.37 kg/day) compared with Nellore cows (6.17 kg/day). There was no effect of the calves' supplementation on BW change (P ≥ 0.11) and BCS change (P ≥ 0.23) of the cows. Therefore, it is concluded that supplementation of beef calves using creep feeding systems in tropical pastures does not affect milk yield, body weight, or body condition of their dams.

Milk isotopic values demonstrate that nursing fur seal pups are a full trophic level higher than their mothers.

RATIONALE: In mammals including humans, mother-to-offspring transfer of nutrients has been the focus of several isotopic studies. Measurement of δ(13) C and δ(15) N values were mainly conducted on easily sampled tissues such as blood and hair that allow the calculation of apparent discrimination factors (∆(13) C and ∆(15) N) between offspring and maternal tissues. Quantifying real ∆(13) C and ∆(15) N values requires the measurement of the δ(13) C and δ(15) N values of milk, the exclusive food of newborns. Surprisingly, little isotopic information is available on milk and its biochemical components (lipids and proteins). METHODS: Paired blood and milk samples from 10 lactating females and their pups were collected from two otariid species, the Antarctic and subantarctic fur seals. Tissue δ(13) C and δ(15) N values were measured using continuous-flow isotope ratio mass spectrometry (CFIRMS) on maternal and offspring blood, and on whole milk, lipid-free milk and milk lipids, thus allowing the calculation and comparison of apparent (maternal blood to offspring blood) and real (lipid-free milk to offspring blood) ∆(13) C and ∆(15) N values. RESULTS: In both fur seal species, the apparent ∆(13) C values averaged ~0.0 ‰. Lipid-free milk was slightly (13) C-depleted compared with both maternal and pup blood and it was strongly (13) C-enriched (~6.3 ‰) compared with milk lipids. In contrast, the apparent and real ∆(15) N values averaged 1.2-1.4 and 2.6-3.0 ‰, respectively, the differences being explained by the ~1.5 ‰ lower milk δ(15) N values than those of maternal blood. CONCLUSIONS: In fur seals, the low apparent ∆(15) N translated into a higher real ∆(15) N value, amounting to a full trophic level, which is in agreement with the almost never verified hypothesis that (15) N differences between mothers and their offsprings should reflect one complete trophic level. The study highlights the need to measure milk isotopic values to disentangle the nutritional mother-to-offspring relationships.

Diet-to-female and female-to-pup isotopic discrimination in South American sea lions.

RATIONALE: The use of accurate, species-specific diet-tissue discrimination factors is a critical requirement when applying stable isotope mixing models to predict consumer diet composition. Thus, diet-to-female and female-to-pup isotopic discrimination factors in several tissues for both captive and wild South American sea lions were estimated to provide appropriate values for quantifying feeding preferences at different timescales in the wild populations of this species. METHODS: Stable carbon and nitrogen isotope ratios in the blood components of two female-pup pairs and females' prey muscle from captive individuals were determined by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS) to calculate the respective isotopic discrimination factors. The same analysis was carried out in both blood components, and skin and hair tissues for eight female-pup pairs from wild individuals. RESULTS: Mean diet-to-female Δ(13) C and Δ(15) N values were higher than the female-to-pup ones. Pup tissues were more (15) N-enriched than their mothers but (13) C-depleted in serum and plasma tissues. In most of the tissue comparisons, we found differences in both Δ(15) N and Δ(13) C values, supporting tissue-specific discrimination. We found no differences between captive and wild female-to-pup discrimination factors either in Δ(13) C or Δ(15) N values of blood components. CONCLUSIONS: Only the stable isotope ratios in pup blood are good proxies of the individual lactating females. Thus, we suggest that blood components are more appropriate to quantify the feeding habits of wild individuals of this species. Furthermore, because female-to-pup discrimination factors for blood components did not differ between captive and wild individuals, we suggest that results for captive experiments can be extrapolated to wild South American sea lion populations.

Providing supplementary milk to suckling dairy calves improves performance at separation and weaning.

Dam rearing can provide health and welfare benefits, but separation and weaning are major welfare challenges. We investigated whether access to an additional source of milk from an automatic milk feeder (AMF) would improve weight gains after separation and weaning. During the first 6wk of life (dam phase), calves were assigned to 1 of 3 treatments using a parallel group design with repeated measures: nursing (n=10) and combined (n=10) calves could suckle from their dams at night (between 2000 and 0800h), and combined calves also had access to 12 L of milk/d accessible 24h/d from an AMF. Milk feeder calves (n=10) also had access to an AMF 24h/d and were housed with the dam at night but were prevented from suckling by an udder net. Separation from the dam occurred after 6wk in 2 phases with decreasing contact between cow and calf: partial separation (duration 4d) and total separation (duration 3d). At separation, all calves were granted access to 12 L of milk 24h/d from the AMF until weaning began at 7wk of age. We hypothesized that access to an AMF during the dam phase would result in less weight loss at separation and weaning compared with calves that had been nutritionally dependent upon the cow (i.e., nursing calves). Calf weight gain during the dam phase averaged (±SD) 1.1±0.26kg/d and did not vary with treatment. Combined calves drank less milk from the AMF compared with milk feeder calves during the dam phase (mean ± SEM daily milk intake: 1.1±0.38 vs. 8.2±0.34 L/d) and tended to drink less during partial separation (6.7±1.28 vs. 9.8±1.02 L/d), but milk intake from the AMF did not differ between these treatments in the later phases. During the same phases, nursing calves consumed less milk from the AMF than the other treatments; of the 10 calves, 6 did not use the AMF (consuming <1.5 L/d) after the dam phase. After separation, nursing calves gained less weight than calves in both the milk feeder and combined treatments (0.8±0.16 vs. 1.2±0.08kg/d). Calves using the AMF after separation (n=23; 4 nursing calves, 9 combined calves, and 10 milk feeder calves) had a higher average daily gain compared with calves that did not (n=7; 6 nursing calves and 1 combined calf; 1.2±0.07 vs. 0.6±0.21kg, respectively). In conclusion, use of the AMF after separation varied, but providing an additional milk source reduced nutritional dependency on the dam, improving calf performance at weaning and separation.

Behavior and body mass changes of a mother and calf Pacific walrus (Odobenus rosmarus divergens) during the suckling period.

The behavior of a 13-year-old female Pacific walrus and her first calf is described during the first 7 months of the 19-month suckling period. The calf vocalized before 62% of suckling sessions. The mother immediately responded after 84% of vocalizations; after 44% she allowed a suckling session. The number of suckling sessions per 24-h period decreased from on average nine in the second week after birth to two by the thirteenth week. Thereafter, the number of suckling sessions fluctuated between 3 and 5/day. The average suckling session duration increased from 4 min/day to around 17 min/day. The average effective suckling time per session increased from on average 2 to 10 min. The number of breaks decreased during the study period from around 40 to 20 per session. The mother spent on average 47% of her time resting, the calf 44%. The remaining time was spent in locomotion, and suckling, playing, investigating, and looking. Mother and calf spent on average 51% of time indoors. The mother spent 43% of her time in the water, the calf 39%. The calf's body mass at birth was 55 kg; it increased to 178 kg at 27 weeks. The mother did not eat for the first 5 days after delivery, and she ate less than usual during the next 6 days. The mother's mass eventually stabilized at 1024 kg (>before gestation). The calf was not given formula and was weaned onto fish. This is the first detailed description of a captive Pacific walrus's suckling period. It could benefit the husbandry of future captive-born walruses, and may elucidate the behavior of wild walruses during suckling.

Daytime mother-calf relationships in reticulated giraffes (Giraffa cameloparadalis reticulate) at the Kyoto City Zoo.

The present study quantitatively assesses the relationships between a reticulated giraffe mother and her first- and second-born calves during the first 22 months of the older calf's and the first 12 months of the younger calf's life at the Kyoto City Zoo, Japan. The mother permitted her calves to suckle at over 70% of their suckling attempts in the first month after their births, and the calves ceased suckling spontaneously in 65 to 70% of the suckling bouts. From the second month on, she showed a clear tendency to reject the calves' suckling attempts and terminated almost all of their suckling bouts, which resulted in approximately 60 sec or less of suckling duration per bout. The frequency of proximity between the mother and her calves remained at 20 to 30% throughout the first year, with no apparent developmental changes being evident. The mother was mainly responsible for terminating proximity by walking away from her calves throughout their first year after birth, while both calves were mainly responsible for attempting proximity by approaching their mother after reaching 2 months of age. Our study also showed that the giraffe mother became pregnant again while nursing her calves and ceased lactation (i.e., weaned the calves) before the fetus's growth started accelerating.

Dab2, megalin, cubilin and amnionless receptor complex might mediate intestinal endocytosis in the suckling rat.

We previously proposed that Dab2 participates in the endocytosis of milk macromolecules in rat small intestine. Here we investigate the receptors that may mediate this endocytosis by studying the effects of age and diet on megalin, VLDLR, and ApoER2 expression, and that of age on the expression of cubilin and amnionless. Of megalin, VLDLR and ApoER2, only the megalin expression pattern resembles that of Dab2 previously reported. Thus the mRNA and protein levels of megalin and Dab2 are high in the intestine of the suckling rat, down-regulated by age and up-regulated by milk diet, mainly in the ileum. Neither age nor diet affect ApoER2 mRNA levels. The effect of age on VLDLR mRNA levels depends on the epithelial cell tested but they are down-regulated by milk diet. In the suckling rat, the intestinal expressions of both cubilin and amnionless are similar to that of megalin and megalin, cubilin, amnionless and Dab2 co-localize at the microvilli and in the apical endocytic apparatus. Co-localization of Dab2 with ApoER2 and VLDLR at the microvilli and in the apical endocytic apparatus is also observed. This is the first report showing intestinal co-localization of: megalin/cubilin/amnionless/Dab2, VLDLR/Dab2 and ApoER2/Dab2. We conclude that the megalin/cubilin/amnionless/Dab2 complex/es participate in intestinal processes, mainly during the lactation period and that Dab2 may act as an adaptor in intestinal processes mediated by ApoER2 and VLDLR.