Energetics and litter size variation in domestic dog Canis familiaris breeds of two sizes

We measured resting metabolic rate (RMR), daily energy expenditure (DEE) and metabolisable energy intake (MEI) in two breeds of dog during peak lactation to test whether litter size differences were a likely consequence of allometric variation in energetics. RMR of Labrador retrievers (30 kg, n = 12) and miniature Schnauzers (6 kg, n = 4) averaged 3437 and 1062 kJ/day, respectively. DEE of Labradors (n = 6) and Schnauzers (n = 4) averaged 9808 and 2619 kJ/day, respectively. MEI of Labradors (n = 12) was 22448 kJ/day and of Schnauzers (a = 7) was 5382 kJ/day. DEE of Labrador pups (2.13 kg, n = 19) was 974 kJ/day and Schnauzers (0.89 kg, n = 7) were 490 kJ/day. Although Labradors had higher MEIs than Schnauzers during peak lactation, there was no difference in mass-specific energy expenditure between the two breeds. Hence, it is unlikely that litter size variation is a likely consequence of differences in maternal energy expenditure. Individual offspring were relatively more costly for mothers of the smaller breed to produce. Therefore, litter size variations were consistent with the expectation that smaller offspring should be more costly for mothers, but not that smaller mothers should per se invest more resources in reproduction. (C) 2001 Elsevier Science Inc. All rights reserved.

Sex differences in responsiveness to begging in a cooperative mammal

In species where young are provisioned by both parents, males commonly contribute less to parental care than females, and are less responsive to variation in begging rates. Similar differences in the care of young occur among adults in cooperative breeders, but fewer studies have investigated whether these are associated with differences in responsiveness. Here, we present results from a playback experiment investigating responsiveness to begging in the meerkat (Suricata suricatta), a cooperatively breeding mammal. Although increased begging rate raised the feeding rate of adults of both sexes, there was no consistent tendency for females to be more responsive than males. However, when we examined changes in the proportion of food items found that were fed to pups (generosity), we found that females were more responsive than males to increased begging rate. These results can be explained in terms of sex differences in dispersal: in meerkats, females are philopatric and receive considerable benefits from investing in young, both directly, by increasing group size, and indirectly, by recruiting helpers if they inherit the breeding position. In addition, they emphasize that generosity provides a more sensitive measure of responsiveness to begging than feeding rate, as it accounts for variation in foraging success. © 2008 The Royal Society.

Signals of need in a cooperatively breeding mammal with mobile offspring

In many bird species with biparental care for young in the nest, hungry chicks beg repeatedly and parents adjust their feeding rate to the call rate of young. Repetitive calling also occurs in fledglings and in some mammals where offspring follow provisioners. It is not yet clear whether, in mobile systems with dispersed young where adults cannot compare the vocal behaviour of all young simultaneously, the calls represent a signal of need. We investigated repetitive begging by cooperatively reared meerkat, Suricata suricatta, pups that foraged with the group. Pups produced two types of begging calls: repeat calls over long periods and high-pitched calls mainly confined to feeding events. Food-deprived pups stayed closer to feeders, and begged for longer and more intensely by calling at a higher rate. Hungry pups increased both the rate of repeat calls, which were given continually, and the number of high-pitched bouts, but adults increased their food allocation only in relation to the rate of repeat calls. Our study indicates that hunger may lead to several changes in vocal behaviour, only some of which may be used by adults to assess need.

Calling in the gap: competition or cooperation in littermates' begging behaviour?

Abstract: Offspring are frequently raised alongside their siblings and are provisioned early in life by adults. Adult provisioning is stimulated by offspring begging, but it is unclear how each offspring should beg, given the begging behaviour of their siblings. It has previously been suggested that siblings may compete directly through begging for a fixed level of provisioning, or that siblings may cooperate in their begging in order to jointly elevate the level of provisioning by adults. We studied the begging behaviour of meerkat Suricata suricatta pups, explored how it changed as the begging behaviour of their littermates altered, and asked how the adults responded to group-level changes in begging. We found conflicting evidence for classic models of competitive and cooperative begging. Pups reared in larger litters begged at higher rates, yet experimentally increasing begging levels within groups caused individual begging rates to decrease. Pups decreased begging rates when close to other begging pups, and pups spaced further apart were fed more. Adults increased their overall level of provisioning as group levels of begging increased, but per capita provisioning decreased. Adults preferred to provision speakers playing back recordings of two pups begging alternately to recordings of the same two pups begging simultaneously. Therefore, we suggest that meerkat pups avoid some of the costs of direct competition imposed by an escalation of begging as other pups beg, by begging in gaps between the bouts of others or avoiding littermates. Such behaviour is also preferred by provisioning adults, thus providing additional benefits to the pups.

High-Frequency Ultrasound Assessment of the Murine Heart From Embryo Through to Juvenile

Aim: The aim of this study is to assess the murine heart of normal embryos, neonates, and juveniles using high-frequency ultrasound. Methods: Diastolic function was measured with E/A ratio (E wave velocity/A wave velocity) and isovolumetric relaxation time (IRT), systolic function with isovolumetric contraction time (ICT), percentage fractional shortening (FS%), percentage ejection fraction (EF%). Global cardiac performance was quantified using myocardial performance index (MPI). Results: Isovolumetric relaxation time remained stable from E10.5 to 3 weeks. Systolic function (ICT) improved with gestation and remained stable from E18.5 onward. Myocardial performance index showed improvement in embryonic lift (0.82-0.63) and then stabilized from 1 to 3 week (0.60-0.58). Percentage ejection fraction remained high during gestation (77%-69%) and then decreased from the neonate to juvenile (68%-51%). Conclusion: The ultrasound biomicroscope allows for noninvasive in-depth assessment of cardiac function of embryos and pups. Detailed physiological and functional cardiac function readouts can be obtained, which is invaluable for comparison to mouse models of disease.

Sibling recognition in the rat

Mechanisms determining the ability of individuals to recognize their kin can be broadly divided into those prenatally determined and those postnatally determined. The role of both of these possibilities was examined in an investigation of sibling recognition in the rat (Rattus norvegicus). Rat pups were tested for their preference for ‘siblings’, (either littermates and genetic siblings—natural siblings; just littermates—any recognition due to postnatal factors; or just genetic siblings—any recognition due to prenatal factors) as opposed to unfamiliar age-mates between the ages of 6 and 22 days, and also for their ability to detect conspecific odour. The results indicate that rats can recognize their siblings (Experiment V) and this can be achieved solely postnatally (Experiments I, VI), or solely prenatally (Experiments II, VII). Other results demonstrated that rats, as early as day 2, and probably earlier, can detect and respond preferentially to conspecific odours (Experiments III, IV and VIII). The possibilities of how these mechanisms, both postnatal and prenatal, function in the acquisition of sibling recognition are discussed. This is the first study in which individuals separated from all genetic relations postnatally are shown to posses the ability to recognize kin.

Novel Protective Properties of IGFBP-3 Result in Enhanced Pericyte Ensheathment, Reduced Microglial Activation, Increased Microglial Apoptosis, and Neuronal Protection after Ischemic Retinal Injury

This study was conducted to determine the perivascular cell responses to increased endothelial cell expression of insulin-like growth factor binding protein-3 (IGFBP-3) in mouse retina. The contribution of bone marrow cells in the IGFBP-3-mediated response was examined using green fluorescent protein-positive (GFP(+)) adult chimeric mice subjected to laser-induced retinal vessel occlusion injury. Intravitreal injection of an endothelial-specific IGFBP-3-expressing plasmid resulted in increased differentiation of GF(P)+ hematopoietic stem cells (HSCs) into pericytes and astrocytes as determined by immunohistochemical analysis. Administration of IGFBP-3 plasmid to mouse pups that underwent the oxygen-induced retinopathy model resulted in increased pericyte ensheathment and reduced pericyte apoptosis in the developing retina. Increased IGFBP-3 expression reduced the number of activated microglial cells and decreased apoptosis of neuronal cells in the oxygen-induced retinopathy model. In summary, IGFBP-3 increased differentiation of GFP(+) HSCs into pericytes and astrocytes while increasing vascular ensheathment of pericytes and decreasing apoptosis of pericytes and retinal neurons. All of these cytoprotective effects exhibited by IGFBP-3 overexpression can result in a more stable retinal vascular bed. Thus, endothelial expression of IGFBP-3 may represent a physiologic response to injury and may represent a therapeutic strategy for the treatment of ischemic vascular eye diseases, such as diabetic retinopathy and retinopathy of prematurity. (Am J Pathol 2011, 178:1517-1524; DOI: 10.1016/j.ajpath.2010.12.031)

Effects of thyroxine treatment on histology and behavior using the methimazole model of congenital hypothyroidism in the rat

The timing of thyroxine (T4) replacement treatment in congenital hypothyroidism (CH) has been suggested to be important for optimizing cognitive recovery in humans; however this has not been fully established using modern animal models of CH. Consequently, the current studies investigated the ameliorating effects of postnatal T4 treatment on neuropathology and behavior in CH rats. Rat dams were administered methimazole to produce CH offspring, then brain tissue from male CH pups was analyzed to determine the effects of postnatal (P3, P7, P14 and P21) T4 treatment on hippocampal dendritic branching and the expression of nerve growth factor (NGF). Two operant behavioral procedures were employed to confirm and extend previous findings obtained using this model, and to investigate timelines for instigating T4 treatment on improved behavioral outcomes. T4 treatment initiated at P14 was protective of a reduction in dendritic branching in the hippocampus, and initiated at P7 was protective of a reduction of NGF expression in the fimbria of the hippocampus. Induction of CH did not affect the acquisition of simple operant response rules but had a significant effect on the acquisition of complex operant rules subsequently imposed. Furthermore, T4 treatment initiated at P3 protected learning deficits seen following the imposition of complex operant response rules. These findings indicate T4 treatment initiated at P7 is sufficient for the protection of hippocampal NGF expression and dendritic branching but for the protection of complex behavioral abilities T4 treatment is necessary prior to or approximating P3.