Measuring cortisol in hair and saliva from dogs: coat color and pigment differences.

Cortisol concentrations are frequently measured from a variety of sources including blood, saliva, urine, and feces to quantify stress in dogs. However, a need still exists for less intrusive collection methods in domestic animals and for more efficient means of measuring basal cortisol. The objectives of the present study were to minimize restraint for saliva sampling, to validate hair for basal cortisol measurement in dogs, and to determine concentrations of cortisol within the hair shaft and in relation to hair color. Using food luring, 79% of dogs required no restraint for saliva collection. Salivary and hair cortisol concentrations were positively correlated (P = 0.001), thus validating hair as a medium for basal cortisol quantification. Black dogs had less cortisol than nonblack dogs (P = 0.039) in hair, but not saliva. Across dogs, the average amount of cortisol did not differ between proximal and distal hair sections (P = 0.348). However, for 7 of the 9 dogs, more cortisol was present in the distal portions of the hair. We observed a difference in cortisol concentrations among hairs of different colors from individual dogs (P = 0.001). From the same 7 x 7 cm ischiatic patch from the same dog, black (eumelanin) hairs were consistently lower in cortisol than yellow (pheomelanin) hairs, and cortisol concentrations of agouti hairs were intermediate. This is the first evidence that hair of different colors might sequester cortisol differently.

Fecal corticosteroids in agouti and non-agouti deer mice (Peromyscus maniculatus).

Total and per gram fecal corticosteroid concentrations were determined for agouti and non-agouti deer mice (Peromyscus maniculatus gracilis) over 24 h under normal caging conditions and after exposure to the stress of novel caging. Per gram corticosteroid concentrations, fecal output, and 24-h corticosteroid production were greater in stressed compared with unstressed deer mice of both color morphs, whereas stressed agoutis had a greater increase in per gram corticosteroid concentrations when compared with non-agoutis. However, due to increased fecal output, stressed non-agouti deer mice had greater 24-h corticosteroid production. Thus, agouti and non-agouti deer mice differ in their hormonal reaction to stress. This is the first demonstration of corticosteroid differences associated with the agouti locus.

Thyroxine levels in agouti and non-agouti deer mice (Peromyscus maniculatus).

Total thyroxine was assessed by radioimmunoassay for 58 female deer mice of two subspecies (Peromyscus maniculatus bairdii and P. m. gracilis) and two color morphs (agouti and non-agouti). P. m. bairdii of both color-morphs had significantly higher mean thyroxine levels than P. m. gracilis. Non-agouti deer mice of both subspecies had significantly higher mean thyroxine levels than agouti deer mice. This is the first report of thyroid hormone differences associated with the non-agouti allele.

Body and organ mass in agouti and non-agouti deer mice (Peromyscus maniculatus).

Body, adrenal, brain, heart, liver, kidney, spleen and testis masses were determined for agouti and non-agouti deer mice (Peromyscus maniculatus gracilis) of both sexes. Body mass was highest for non-agouti females and lowest for agouti females; and sex differences in body mass were significant for agouti, but not non-agouti, deer mice. Adrenal, brain and liver masses were similar between color morphs; heart mass was greater in agouti males; and kidney, spleen and testis masses were all significantly greater for non-agouti deer mice. Splenomegaly in non-agouti deer mice was prominent, as spleens of non-agouti deer mice were 50% larger than those of agouti animals. Sex differences varied across organs and color morphs. For both color morphs, males had heavier adrenals and brains, whereas females had heavier livers and spleens. Kidney and heart mass was greater for female non-agouti deer mice, but for agouti animals, heart mass was greater in males and kidney mass differed little between the sexes. For both color morphs, testes and spleen mass was altered by photoperiod in 72 deer mice housed under short- or long-day conditions and the effect was stronger in non-agouti animals. This is the first report of splenomegaly and sex-specific body mass differences associated with the non-agouti allele.

Influence of social status on ovarian function in farmed red deer (Cervus elaphus).

This study examines the effects of behavioural and environmental factors on ovarian function in red deer hinds. Patterns of postovulatory luteal progesterone secretion were investigated in groups of farmed red deer hinds following oestrus induced by progesterone administration and withdrawal. Hinds were held under conditions leading to low (Experiment 1, held in paddocks: 0.29 per animal/h) or high (Experiment 2, held in pens: 1.11 per animal/h) interaction rates, and progesterone was measured in jugular venous blood samples obtained daily for 14 days after ovulation. Plasma progesterone levels tended to differ with respect to dominance status in both experiments (p < 0.1). Progesterone levels were substantially lower following prolonged hot dry weather (mean 0.67 +/- SEM 0.03 ng/mL) than in a year of relatively typical climatic conditions (mean 1.63 +/- 0.04 ng/mL; p < 0.0005). Progesterone levels were not related to the body weight of the hinds, and were not affected by housing conditions leading to different interaction rates. We conclude that although there is a tendency for dominance status to affect ovarian function, as observed before, this relationship is obscured in farmed red deer where all animals in the herd enjoy a higher plane of nutrition and movements of individuals between groups confuse dominance relationships.

Effect of transatlantic transport on reproduction of agouti and nonagouti deer mice, Peromyscus maniculatus.

In conjunction with establishing colonies of deer mice in the UK, effects of transportation on reproduction in agouti (A) and nonagouti (a) deer mice were assessed. Adults were shipped via ground courier and air freight from Northampton, Massachusetts, USA to Sutton Bonington, Leicestershire, England in February and June. Deer mice were paired upon arrival in Sutton Bonington, whereas matched controls were paired in the original colonies at shipping. To assess reproduction, the following variables were monitored for 110 days for all 96 pairs: number of pairs producing litters, time from pairing to birth, interlitter interval, litter size at birth, and litter size at weaning. Generally, shipping suppressed litter production and delayed its timing, but had less effect on litter size. Overall, 32 of 48 control pairs (67%) produced 69 litters compared with 37 litters from 21 of 48 pairs (44%) after shipping. Pairing-to-first-litter intervals were approximately two oestrous cycles shorter in control animals (39 vs 53 days). Averaged over all litters, litter size was higher in control pairs (4.4 vs 4.0). With respect to genotype, control agouti deer mice were less productive than nonagouti animals, but they reproduced better than nonagoutis after shipping. In control animals, colourmorphs did not differ with respect to litter production or timing, but agouti pairs had smaller litters (first litter: A: 3.1, a: 4.2) and this difference increased at successive litters (third litter A: 3.9, a: 6.0). After shipping, agouti animals produced more litters (A: 22, a: 15), and did so earlier (pairing to birth: A: 47 days, a: 60 days), as well as more frequently (interlitter interval: A: 32 days, a: 51 days). Litter size was also more similar between genotypes after shipping (A: 4.0, a: 4.1). Overall, control agouti animals produced 37% fewer offspring than nonagouti pairs. (A: 116 neonates, a: 185 neonates), but after shipping agouti deer mice produced 43% more offspring than nonagouti animals (A: 87 neonates, a: 61 neonates). In sum, transport stress suppressed reproduction for several weeks after shipping and this suppression was exacerbated in nonagouti deer mice.

Effects of the nonagouti coat-color allele on behavior of deer mice (Peromyscus maniculatus): a comparison with Norway rats (Rattus norvegicus).

The agouti locus influences coat color by antagonizing melanocyte-stimulating hormone (MSH) at its receptor on pigment cells and may antagonize MSH in neural tissue. This study replicates work on rats to assess whether behavioral (neural) effects of the agouti locus are as similar across mammals as those on coat color. Handling, open-field, platform jump, and food-novelty tests were conducted on agouti and nonagouti deer mice (Peromyscus maniculatus) following protocols in C. A. Cottle and E. O. Price (1987). As with rats, nonagouti deer mice were less aggressive, less active, and easier to handle compared with their agouti counterparts. Nonagouti deer mice also groomed more than agouti subjects. Thus, behavioral effects of the agouti locus are conservative, and agouti may be an important modulator of melanocortins in neural as well as integumentary tissue.

Empirical and theoretical constraints on the evolution of lactation.

For 829 mammalian species, data on age at weaning or age at first solid food were analyzed with respect to body mass, phylogeny, habitat, diet, length of gestation, basal metabolism, and neonatal development. The primary influence on lactation length is female mass, but phylogenetic constraints are important. Thus, lactation can be characterized as short (earless seals and baleen whales), long (marsupials, bats, and primates), or average (remaining eutherians). Among average mammals, lagomorphs have short lactations. Lactation may have different functions, evolutionary constraints, and physiological control depending on whether young first eat solid food near weaning or well before it. First solid food eaten near weaning occurs in polytocous species with altricial young; in this case, lactation has a clear energetic role. In contrast, first solid food well before weaning is common for mammals with single, precocial offspring. For these species, the energetic and nutritional constraints on lactation may be less important than the benefits of maintaining contact between mother and young, such as reduced juvenile mortality and increased opportunities for learning social or foraging patterns. Thus, the age at first solid food relative to the age at weaning may indicate the function of lactation within the reproductive biology of a given mammal. Delayed development and implantation alter the timing of energetic investment during gestation, so too, the age at first solid food may alter or reflect the rate of energetic investment during lactation. Thus, the age at first solid food relative to the age at weaning may indicate the function of lactation within the reproductive biology of a given mammal. Testing these hypotheses will require data from diverse species on the nutritional and energetic value of milk before and after first solid food as well as on the mechanics and consequences of nursing or suckling during the course of lactation.

Basal metabolic rates in mammals: taxonomic differences in the allometry of BMR and body mass.

No single equation adequately describes the allometric relation between body mass and BMR for mammals. Least squares regression of log-transformed data for 248 eutherian species results in a line with a slope (-0.30) significantly different from that of Kleiber's line (-0.25). Interordinal comparisons of least squares regressions of log-transformed BMR and mass suggest that the Insectivora have a significantly steeper slope to their allometric relationship than do most other orders, while the non-insectivore orders are statistically homogeneous with respect to slope. With respect to elevation, Edentata have the lowest BMRs; Marsupialia, Primates and Chiroptera are indistinguishable from each other but above the edentates; Primates, Chiroptera, Rodentia, Lagomorpha and Carnivora form the next highest homogeneous grouping; and Artiodactyla have the highest BMRs, significantly greater than all but Lagomorpha and Carnivora. Analysis of intraordinal variation within the Rodentia suggests significant heterogeneity among families in BMR-mass allometry.

Basal metabolic rate and the intrinsic rate of increase: An empirical and theoretical reexamination.

A reanalysis of data presented by Henneman (1983) to examine the relationship between intrinsic rate of increase and basal metabolism suggests there is no statistically significant correlation between the two variables when both are treated with comparable statistical techniques. In addition, I suggest there is no theoretical reason to expect a high correlation between basal metabolic rate and a population's maximum rate of increase.

Care and breeding of the gray, short-tailed opossum (Monodelphis domestica)

Husbandry procedures were developed for the gray short-tailed opossum (Monodelphis domestica) based on experience with several colonies that were self-sustaining for up to 4 years (five generations). Individual adult animals (80-155 g) were maintained in modified single rat or guinea pig cages, although larger cages with floor areas of at least 2,000 cm2 were required for breeding. Diets consisted primarily of ground meat, dried milk powder, wheat germ, and vitamin supplements. Switching males in the breeding pairs stimulated reproductive activity. Monodelphis domestica was found to be hardy, tractable, and able to reproduce throughout the year under laboratory conditions. This species is proposed as a practical marsupial model for biomedical research.

Separation of molecular species of sphingomyelin by reversed-phase high-performance liquid chromatography.

A convenient method for the separation of molecular species of sphingomyelin by reversed-phase high-performance liquid chromatography (HPLC) is described. Sphingomyelin species from bovine brain and sheep and pig erythrocytes were resolved into 10-12 separate peaks on a micro -BondaPak C(18) or Nucleosil-5-C(18) reversedphase column with methanol-5 mM potassium phosphate buffer, pH 7.4, 9:1 (v/v) as the solvent. Detection was at 203-205 nm. The sphingomyelin species were primarily resolved due to specific hydrophobic interaction of their fatty acid and sphingoid chains with the alkyl ligand of the stationary phase. The retention time of the sphingomyelin species increased progressively as the number of carbon atoms in the hydrophobic chains increased in the homologous series. The presence of one double bond in the molecule reduced the retention time significantly. Introduction of a second double bond in the fatty acid side chain did not reduce the retention time to the same extent as the first double bond. The presence of a trans double bond in the sphingoid moiety increased the retention time of sphingomyelin more than did a cis double bond in the fatty acid side chain. The differential hydrophobic interaction observed between the ligand of the stationary phase and different alkyl chains of the sphingomyelin species illustrates that reversed-phase HPLC technique can be conveniently used to study the extent of relative hydrophobicity of different types of alkyl chains.-Jungalwala, F. B., V. Hayssen, J. M. Pasquini, and R. H. McCluer. Separation of molecular species of sphingomyelin by reversed-phase high-performance liquid chromatography.