Serum concentration dynamic of energy homeostasis hormones, leptin, insulin, thyroid hormones, and cortisol throughout canine pregnancy and lactation

Body Condition and Fertility in Dogs

Ideal body condition and nutritional status in dogs is essential for quality of life, including reproductive health. Herein, we review the implications body condition, particularly fat, has on puberty, fertility, pregnancy, and parturition in dogs. Ideal body condition at puberty is necessary for dogs to achieve sexual maturity and reproduce. Moreover, over and under conditioned female dogs have increased risk of adverse pregnancy, parturition, and neonatal outcomes. Less is known about body condition and male dog fertility but some evidence is provided in this article. Finally, recommendations for maintaining an ideal body condition in intact adult dogs for optimal fertility are provided.

Thyroid hormones in canine pregnancy and lactation

It is believed that thyroid function has a significant effect on fertility and fetal development in mammals. So far, however, only few studies have been published about potential effects of the reproductive cycle stage on thyroid hormone concentrations in dogs. Therefore, over the course of 122 pregnant and non-pregnant cycles in healthy bitches, Thyroid stimulating hormone (TSH), free Thyroxine (fT4), total Thyroxine (tT4) and Progesterone (P4) were measured six times to assess the influence of the cycle stage and pregnancy on hormone concentrations. The aim was to evaluate established reference intervals for the thyroid hormones in a female study population. Of the 122 bitches, 98 became pregnant. Blood samples were collected during estrus, three times in pregnancy, during lactation and after weaning, or at equivalent times during and after estrus in non-pregnant dogs. No differences between pregnant and non-pregnant animals in any of the thyroid hormones were found. Hormone concentrations, however, differed significantly between the six samplings (p < .01). TSH initially declined during pregnancy, then rose again. The mean concentration of all dogs exceeded the overall upper reference limit of 0.70 ng/mL during lactation. Concentrations of tT4 and ft4 increased during the first third of pregnancy and then subsequently declined. The overall reference limits for tT4 were 0.47-3.20 μg/dL, and for fT4 4.86-29.60 pmol/L, but the reference intervals varied between the sampling dates. The observed patterns may reflect that maternal tT4 and fT4 seem to have important effects during early pregnancy, including a pronounced negative feedback effect on TSH. The initial increase and subsequent decline of tT4 and fT4 concentrations during the course of pregnancy is in accordance with findings in humans and may support the development of fetal thyroid function. The observed peak of TSH concentrations during lactation suggests that the demand for thyroid hormones in this phase is largest. Even if the underlying causes and mechanisms of thyroid regulation are not fully understood, the results of this study show relevant changes of hormone concentrations in the course of the sexual cycle and pregnancy. In that regard, cycle stage needs to be considered when assessing thyroid function in bitches.

Metabolomics during canine pregnancy and lactation

During pregnancy and parturition, female dogs have to cope with various challenges such as providing nutrients for the growth of the fetuses, hormonal changes, whelping, nursing, milk production, and uterine involution. Metabolomic research has been used to characterize the influence of several factors on metabolism such as inter- and intra-individual factors, feeding, aging, inter-breed differences, drug action, behavior, exercise, genetic factors, neuter status, and pathologic processes. Aim of this study was to identify metabolites showing specific changes in blood serum at the different phases of pregnancy and lactation. In total, 27 privately owned female dogs of 21 different breeds were sampled at six time points: during heat, in early, mid and late pregnancy, at the suspected peak of lactation and after weaning. A validated and highly automated canine-specific NMR metabolomics technology was utilized to quantitate 123 measurands. It was evaluated which metabolite concentrations showed significant changes between the different time points. Metabolites were then grouped into five clusters based on concentration patterns and biochemical relationships between the metabolites: high in mid-pregnancy, low in mid-pregnancy, high in late pregnancy, high in lactation, and low in lactation. Several metabolites such as albumin, glycoprotein acetyls, fatty acids, lipoproteins, glucose, and some amino acids show similar patterns during pregnancy and lactation as shown in humans. The patterns of some other parameters such as branched-chain amino acids, alanine and histidine seem to differ between these species. For most metabolites, it is yet unstudied whether the observed changes arise from modified resorption from the intestines, modified production, or metabolism in the maternal or fetal tissues. Hence, further species-specific metabolomic research may support a broader understanding of the physiological changes caused by pregnancy that are likely to be key for the normal fetal growth and development. Our findings provide a baseline of normal metabolic changes during healthy canine pregnancy and parturition. Combined with future metabolomics findings, they may help monitor vital functions of pre-, intra-, and post-partum bitches and may allow early detection of illness.

Dam (Canis familiaris) Welfare throughout the Peri-Parturient Period in Commercial Breeding Kennels

Simple Summary

Welfare problems experienced during gestation and lactation may negatively affect dams and their puppies. However, the welfare states of dams in commercial breeding (CB) kennels during this period have not been well examined. Therefore, we examined a range of behavioral, physical, and physiological metrics throughout the period around parturition to identify if changes indicative of impaired welfare were present. We tested 74 dams from eight CB kennels at 6 and 1 week prepartum, and 4 and 8 weeks postpartum. At each time point we measured their responses to a stranger approaching, their physical health, and indicators of their stress response, immune function, and parasite burden. Findings did not reveal major changes in dam welfare. Most changes observed were likely because of natural biological changes resulting from pregnancy, lactation, and weaning. However, as some changes in metrics deviated from what was expected and there were changes in environmental and management factors during this time, future research should identify how they affect dam welfare.

Abstract

Poor dam welfare throughout the peri-parturient period can also negatively affect that of their offspring. This study aimed to identify changes in physical, physiological, and behavioral metrics indicative of dam welfare throughout the peri-parturient period. Dams (n = 74) from eight U.S. Midwest commercial breeding (CB) kennels were tested at 6 and 1 week prepartum, and 4 and 8 weeks postpartum. At each time point dams underwent a stranger approach test, physical health assessment, hair collection for hair cortisol concentration (HCC) and fecal collection for fecal glucocorticoid metabolites (FGM), fecal secretory immunoglobulin A (sIgA) and parasite detection. Linear mixed-effects models indicated dams exhibited more affiliative behaviors towards the stranger at 4 weeks postpartum than 6 weeks prepartum (p = 0.03), increased HCC from 4-weeks to 8 weeks postpartum (p = 0.02), and increased FGM from 1 week prepartum to 8 weeks postpartum (p = 0.04). At each respective time point, the percentage of dams with intestinal parasites was 11%, 4%, 23%, and 15%. Most changes are likely due to increased energy requirements and hormonal variations. However, deviations from expected changes may have resulted from changes in environment and/ or management, which should be explored in future studies.

Dead or Alive? A Review of Perinatal Factors That Determine Canine Neonatal Viability

Simple Summary

The article summarizes the current knowledge on factors related to pregnancy, parturition, and newborns that affect the health status of a puppy and determine its chances for survival and development. The detailed information is provided in terms of breed predispositions, objectives of pregnancy monitoring, potential sources of complications, and veterinary advances in care and treatment of perinatal conditions. Successful pregnancy outcomes still pose challenges in veterinary neonatology; thus, publications presenting the current state of knowledge in this field are in demand.

Abstract

The perinatal period has a critical impact on viability of the newborns. The variety of factors that can potentially affect the health of a litter during pregnancy, birth, and the first weeks of life requires proper attention from both the breeder and the veterinarian. The health status of puppies can be influenced by various maternal factors, including breed characteristics, anatomy, quality of nutrition, delivery assistance, neonatal care, and environmental or infectious agents encountered during pregnancy. Regular examinations and pregnancy monitoring are key tools for early detection of signals that can indicate disorders even before clinical signs occur. Early detection significantly increases the chances of puppies’ survival and proper development. The purpose of the review was to summarize and discuss the complex interactions between all elements that, throughout pregnancy and the first days of life, have a tangible impact on the subsequent fate of the offspring. Many of these components continue to pose challenges in veterinary neonatology; thus, publications presenting the current state of knowledge in this field are in demand.

The effect of aggression II: Acclimation to a high ambient temperature reduces territorial aggression in male striped hamsters (Cricetulus barabensis)

Thyroid hormones have a profound influence on development, cellular differentiation and metabolism, and are also suspected of playing a role in aggression. We measured territorial aggression, body temperature (T_b) and serum thyroid hormones levels of male striped hamsters (Cricetulus barabensis) acclimated to either cold (5 °C), cool (21 °C) or hot (34 °C) ambient temperatures. The effects of methimazole on territorial aggression, food intake, metabolic rate and serum thyroid hormone levels, were also examined. Territorial aggression was significantly lower in male hamsters acclimated to the hot temperature compared to those acclimated to the cool or cold temperatures. T_b significantly increased during aggressive territorial interactions with intruders but did not significantly differ among the three temperature treatments. Serum T₃, T₄ and cortisol levels of hamsters acclimated to 34 °C were significantly lower than those acclimated to 21 °C. In addition to significantly reducing territorial aggression, treatment with methimazole also significantly reduced serum T₃ and T₄ levels, T_b and metabolic rate. These results suggest that exposure to high temperatures reduces the capacity of hamsters to dissipate heat causing them to lower their metabolic rate, which, in turn, causes them to reduce territorial aggression to prevent hyperthermia. The lower metabolic rate mediated by down-regulated thyroid hormones inhibits territorial aggression and could thereby determine the outcome of territorial conflicts.

How Stressful Is Maternity? Study about Cortisol and Dehydroepiandrosterone-Sulfate Coat and Claws Concentrations in Female Dogs from Mating to 60 Days Post-Partum

In dogs, the phase from mating to the end of weaning lasts about 120 days and encompasses many aspects that, interacting, contribute to increase the allostatic load. The coat and claws, useful for long-term change assessments, have the advantage of being collectable without invasiveness. In the present study, the Cortisol (C) and Dehydroepiandrosterone-sulfate (DHEA-S) concentration monthly changes in the coat and claws were studied in female dogs from mating to the end of weaning to assess Hypothalamic-Pituitary-Adrenal (HPA) axis activation during pregnancy and the post-partum period. The results from 15 Dobermann Pinscher female dogs showed a trend of increase of the coat C from mating to 60 days post-partum, with significant changes between mating and parturition-60 days post-partum (p < 0.01) and between the 30-day pregnancy diagnosis (PD) and 30-60 days post-partum (p < 0.05). The claws C trend showed significant increases between mating and 30-60 days post-partum (p < 0.05) and between the PD and 60 days post-partum (p < 0.01). DHEA-S in both matrices showed non-significant changes. The results suggest that maternity could play a pivotal role in the HPA axis activation, with a subsequent chronic secretion of C determining an increase in the allostatic load in the mothers. Neither maternal parity nor litter size played a significant role in the accumulation of C and DHEA-S in both matrices.

How the kinetic behavior of organic chickens affects productive performance and blood and meat oxidative status: a study of six poultry genotypes

The aim of this study was to analyze the relationship between the kinetic behavior, carcass characteristics, oxidative status (blood and meat), and meat fatty acid profiles of 6 organically reared slower growing chicken genotypes (SrG). One hundred male chickens of 6 SrG were used: Ranger Classic (RC), Ranger Gold (RG), Rowan Ranger (RR), RedJA (RJ), CY Gen 5 JA87 (CY), and M22 × JA87 (M). Twenty chickens/genotype were selected to analyze behavior, while, 15 individuals were slaughtered and different traits were analyzed in the blood and drumstick meat. The variables were grouped into different principal components: kinetic activity (PC1, with explorative attitude as the highest score), productive performance (PC2, carcass and head/feet yields), blood (PC3, carbonyls, and TBARS) and meat (PC6, thiols, and TBARS) markers, technological traits (PC4, pH, and color), proximate meat composition (PCA5, moisture, lipids, protein, and ash), fatty acid profile, and nutritional indexes (PC7, IP, and PUFAn-3). Uni- and bivariate analyses showed a strong positive association between kinetic behaviors and blood and meat oxidation and a medium positive association with fatty acid profile and nutritional indexes, whereas a negative association was found between productive performance loads and the technological traits of meat. Generalized linear models showed that all PCs were influenced by genotype. In particular, CY and M resulted as less active genotypes; conversely, RR showed more kinetic activity, whereas RJ, RG, and RC exhibited intermediate levels of activity. Cluster analysis of kinetic behavior and blood or meat oxidative status highlighted 2 groups: nonwalking (NW: CY and M) and walking (W: RC, RG, RR, and RJ) animals. However, in the W group, another was visualized, constituted by genotypes with high kinetic activity resulting in the worst oxidative balance (Walking not trained-genotypes, Wnt: RR and RJ). The present results confirmed that the kinetic behavior of SrG genotypes is negatively correlated with productive performance. Furthermore, a significant association between kinetic behavior and blood (positively correlated) or meat (negatively correlated) oxidative status was noted. Such differences are mainly due to the intrinsic response of the genotypes used (i.e., training-walking capacity).

Implications of the RhoA/Rho associated kinase pathway and leptin in primary uterine inertia in the dog

The underlying functional and molecular changes in canine primary uterine inertia (PUI) are still not clarified. Leptin (Lep) and obesity negatively affect uterine contractility in women, partly mediated by the RhoA/Rho associated kinase pathway, affecting myometrial calcium sensitization. We hypothesized that increased uterine Lep/Lep receptor (LepR) or decreased RhoA/Rho associated kinase expression contributes to PUI in dogs, independent of obesity. Dogs presented for dystocia were grouped into PUI (n = 11) or obstructive dystocia (OD, still showing strong labor contractions; n = 7). Interplacental full-thickness uterine biopsies were collected during Cesarean section for relative gene expression (RGE) of RhoA, its effector kinases (ROCK1, ROCK2), Lep and LepR by qPCR. Protein and/or mRNA expression and localization was evaluated by immunohistochemistry and in situ hybridization. RGE was compared between groups by one-way ANOVA using body weight as covariate with statistical significance at P < 0.05. Uterine ROCK1 and ROCK2 gene expression was significantly higher in PUI than OD, while RhoA and Lep did not differ. LepR RGE was below the detection limit in five PUI and all OD dogs. Litter size had no influence. Lep, LepR, RhoA, ROCK1, ROCK2 protein and/or mRNA were localized in the myometrium and endometrium. Uterine protein expression appeared similar between groups. LepR mRNA signals appeared stronger in PUI than OD. In conclusion, lasting, strong labor contractions in OD likely resulted in downregulation of uterine ROCK1 and ROCK2, contrasting the higher expression in PUI dogs with insufficient contractions. The Lep-LepR system may affect uterine contractility in non-obese PUI dogs in a paracrine-autocrine manner.

Impact of Goji Berries (Lycium barbarum) Supplementation on the Energy Homeostasis of Rabbit Does: Uni- and Multivariate Approach

Simple Summary

The energy balance during the reproduction cycle is a problematic issue for livestock species because it has consequences not only on animal welfare but also on the profitability of the farm. The adoption of new nutritional strategies could improve both of these aspects. In the present study, the supplementation with goji berries was proposed and evaluated on the rabbit, which is both a livestock animal and a useful animal model. Goji berry is the fruit of Lycium barbarum that is a natural resource made up of several compounds with biological activities and their consumption could be beneficial for the health and the general well-being of humans and animals. Its effect on several hormones and metabolites involved on energy balance of rabbit doe were evaluated by using both uni- and multivariate approach. Our finding, in addition to describing the intricate relationships between body conditions, hormones and metabolites during pregnancy and lactation, suggested that the supplementation with goji berry in the rabbit diet at low percentage could improve some aspects of energy metabolism and, in particular, doe’s insulin sensitivity. Conversely, the intake of high doses of goji raises concerns due to the risk of excessive fattening and worsening of insulin resistance.

Abstract

This study examined the effects of goji berries dietary supplementation on the energetic metabolism of doe. Thirty days before artificial insemination, 75 New Zealand White does were assigned to three different diets: commercial standard diet (C) and supplemented with 1% (LG) and 3% (HG) of goji berries, respectively. Body conditions, hormones and metabolites were monitored until weaning. Body weight and BCS were higher in HG than C (p < 0.05). LG showed lower T3/T4 ratio and cortisol concentrations (p < 0.05) and tended to have lower indices of insulin resistances (p < 0.1) than HG. Compared to control, leptin was higher in HG at AI (p < 0.01) and in LG during lactation (p < 0.05). Two principal components were extracted by multivariate analysis describing the relationships between (1) non-esterified fatty acids, insulin and glucose levels, and (2) body conditions and leptin metabolism. The first component highlighted the energy deficit and the insulin resistance of the does during pregnancy and lactation. The second one showed that leptin, body weight and Body Condition Score (BCS) enhance as levels of goji berries in the diet increase. Thus, the effects of goji supplementation are dose-dependent: an improvement on energy metabolism was achieved with a low-dose while the highest dose could determine excessive fattening and insulin resistance in does.

Energy homeostasis in rabbit does during pregnancy and pseudopregnancy

This study was conducted to evaluate the changing concentrations of metabolic hormones and metabolites in pregnant (P) and pseudopregnant (PP) rabbit does. Twenty-five New Zealand White rabbit does were submitted to artificial insemination (AI) and then classified as P (n = 15) or PP (n = 10). Blood samples were collected weekly until day 32 post AI. During pregnancy, leptin concentrations were greater on Days 14 and 21 (P < 0.05), while insulin was greater on days 21 and 32 post AI (P < 0.05) compared to PP does. The triiodothyronine/thyroxine (T3/T4) ratio was greater in the first and last week (P < 0.001); whereas, cortisol concentrations were greater in the last week of pregnancy and after parturition (P < 0.01) compared with that of PP does. Non-esterified fatty acids (NEFA) concentrations increased from day 7 until day 32 post AI (P < 0.05). Glucose concentrations were unchanged throughout pregnancy although concentrations were positively associated with litter size. These results indicate concentrations of hormones and metabolites change during pregnancy to ensure energy requirements are met for both the foetuses and the maternal tissues. Physiological hyperleptinemia, hyperinsulinemia, and changes in cortisol as well as thyroid hormones indicate there is an adaptation of metabolic functions induced by pregnancy. These adaptations could be mediated by gonadal steroids because changes mainly occur in the second half of pregnancy when the profile of the sex hormones differs between P and PP does.

Stressed by Maternity: Changes of Cortisol Level in Lactating Domestic Cats

Lactation is the most energetically expensive component of maternal care in mammals. Increased reproductive investment can lead to physiological stress for the mothers, based on the exhaustion of energy resources and increase in glucocorticoids level. This study aimed to estimate the changes in cortisol concentrations during lactation in domestic cats and compared the differences among litter sizes. Eleven females gave birth to 27 litters, which were divided in two groups-small (1-3 kittens) and large (4-7 kittens) litters. Blood samples were collected from each female before mating, after parturition, at 4 and 8 weeks of lactation. We showed that the cortisol level in females changed significantly during lactation-the highest concentrations were observed at the peak of lactation at 4 weeks. Cortisol levels varied significantly among females but did not depend on their maternal experience. We also revealed that there were no differences in cortisol levels between females with small and large litters, but at 4 weeks of lactation, the hormone concentrations were higher in females with small litters. It is likely that these females initially invested less in reproduction, giving birth to fewer offspring.

Effect of breed body-size on leptin amniotic fluid concentrations at term pregnancy in dogs

Because of the need to improve the knowledge about canine perinatology, and given the major role of fetal fluids in sustaining the course of pregnancy and fetal development, an in-depth analysis to better understand the role of some hormones in these compartments is essential. Among all, leptin is recognized to play a key role not only on the energetic homeostasis, but also at multiple levels, influencing the control of reproduction, food assumption and metabolism. Even if in humans and other species it is reported the presence of leptin receptors during fetal development, very little is known about the canine species, in which the role of leptin still needs to be fully understood. The present study aimed to assess the amniotic fluid leptin (AFL) concentrations at term pregnancy in healthy dogs, and to evaluate the possible influence played by breed body-size (after assessment of correlation with maternal bodyweight and placental weight), or other maternal (age, parity, and the so-called "litter effect") and neonatal (gender, birth weight, litter size) parameters on AFL concentrations, analyzed by ELISA test. The study was performed on 90 healthy, viable and normal weighted puppies, 39 small-sized (adult body weight < 10 kg) and 51 large-sized (adult body weight > 25 kg), born by 29 purebred, healthy bitches, submitted to elective Caesarean section because of breed-related or individual high risk for dystocia. The results showed that the mean AFL concentration in the small-sized puppies was significantly (p < 0.05) higher in comparison to large-sized puppies (867.48 vs 698.42 pg/ml), while all the other studied parameters did not show to influence AFL concentrations. In conclusions, the present study showed significant higher at term AFL concentrations in small-sized as compared to large-sized breeds, suggesting an influence of breed body-size on fetal metabolism, as previously reported for NEFA and IGF-I.

Serum concentrations of leptin in pregnant and non-pregnant bitches

Leptin regulates body weight and several physiological processes including reproduction. We evaluated the circulating levels of leptin in pregnant and non-pregnant bitches as well as their correlation with body weight, food intake and number of foetuses. Nineteen healthy German shepherd bitches were used and divided in two groups (pregnant n = 12 and non-pregnant n = 7). Blood samples were collected every 15 days starting from ovulation (Day 0) throughout pregnancy (pregnant group, P) or throughout luteal phase (non-pregnant group, NP) In pregnant bitches, leptin concentrations increased from the day of ovulation (1.32 ± 0.06 ng/ml) up to day 45 (1.51 ± 0.06 ng/ml; p < .01) and returned to baseline values from day 60 post-ovulation. In non-pregnant bitches, leptin concentrations remained constant throughout the whole observation period (estimated marginal mean ± SE=1.33 ± 0.38 ng/ml). Pairwise comparisons showed significant differences between P and NP at day 45 post-ovulation (p < .05). Multivariable models indicated that, controlling for time and litter size, there was a positive relationship between leptin concentration and BW (p < .05) although Pearson coefficients showed that the correlation between BW and leptin was only significant in NP animals at day 45 (r = 0.76, p < .05). The multivariable approach also suggested that, holding BW and time constant, leptin concentrations tend to increase as the number of puppies increased (p = .06). Our study supports indirectly the contribution of the feto-placental unit to the circulating maternal leptin concentration.

Levothyroxine supplementation in hypothyroid bitches during pregnancy

Hypothyroidism is the most common endocrine disease in dogs and has been shown to have a hereditary nature in many breeds. Previous studies have documented decreased fertility in bitches with experimentally-induced hypothyroidism, decreased viability at birth, increased periparturient mortality, and reduced birth weight in pups born to hypothyroid dogs. Hypothyroid women have an increased demand for exogenous thyroxine throughout gestation in order to maintain normal plasma concentrations of thyroid hormones and produce neuropsychologically normal children. This study was performed to determine if pregnancy causes a similar need for increased levothyroxine dosages in dogs to maintain a euthyroid state. Serum was harvested from blood collected from six bitches with experimentally-induced hypothyroidism that were receiving standard thyroid hormone replacement therapy and from four euthyroid control bitches. Thyroid function tests performed on these samples included total thyroxine (T₄), free T₄ (fT₄), thyroid stimulating hormone (TSH), and 3,5,3'-triiodothyronine (T₃). Thyroid function tests were measured from ovulation through the end of pregnancy. All bitches whelped normal litters. Euthyroid bitches had no significant alterations in their hormone concentrations throughout pregnancy. None of the supplemented hypothyroid bitches had clinical signs of hypothyroidism throughout the study. Serum concentrations of T₄ and fT₄ were elevated compared to ovulation at multiple sample points during gestation in supplemented dogs. The results from this study indicate that standard levothyroxine supplementation is adequate to maintain a euthyroid state during pregnancy in experimentally-induced hypothyroid dogs. In addition, there is no evidence that canine thyroid profiles in euthyroid dogs are altered during gestation.

Effect of maternal metabolism on fetal supply: Glucose, non-esterified fatty acids and beta-hydroxybutyrate concentrations in canine maternal serum and fetal fluids at term pregnancy

The progressive adaptations in carbohydrate and lipid metabolism during canine pregnancy are reflected in the concentrations of glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). The levels of these metabolites in the bitch likely affect fetal concentrations and the composition of amniotic and allantoic fluids (AMF and ALF, respectively). We studied 31 canine parturitions (Cesarean sections) and found that glucose, NEFA and BHB concentrations were significantly higher in maternal serum than in AMF or ALF. Glucose levels in maternal serum, AMF and ALF were closely related (R² ≥ 0.821, P < 0.0001) as well as serum and AMF BHB levels (R² = 0.661, P < 0.0001). In maternal serum, increases in NEFA were associated with increased BHB, and both were negatively related to glucose (P ≤ 0.010). To estimate the effect of the metabolic burden of pregnancy, we evaluated these variables in relation to the dam's body weight and to the ratio of litter weight to the dam's body weight (LW/BW). Maternal serum glucose was not influenced by LW/BW, but it was lower in small than in large/giant bitches. Small breed dogs and those with >10% LW/BW had significantly higher serum NEFA and BHB concentrations. Glucose in AMF and ALF was independent of LW/BW (P ≥ 0.399). AMF NEFA was lower and BHB higher, if LW/BW was >10% (P ≤ 0.048). In conclusion, the extent of the metabolic load of pregnancy in bitches depends on breed size and on the ratio of litter weight to dam's body weight. Maternal concentrations of glucose, BHB and NEFA determine the concentrations of these metabolites in fetal fluids.