There have been marked changes in amylase gene number during human evolution resulting in shifts in carbohydrate metabolism. This has been related to utilization of starch. Similarly, there are changes in enzymes related to carbohydrate metabolism in dogs. Again, this has been linked to improving starch utilization following domestication. It was questioned as circulating concentrations of glucose is a good indicator of putative differences in carbohydrate metabolism across domesticated animals. Domesticated bovids had lower (p < 0.001) circulating concentrations of glucose than wild species in their respective subfamilies. Circulating concentrations of glucose were consistently lower (p < 0.001) in domesticated animals compared to either closely related wild species or the mean for wild species in their subfamilies (or families where there is insufficient data available). It is suggested that shift to lower circulating concentrations of glucose in domesticated animals is related to greater starch intake following domestication in a manner akin to the shifts in carbohydrate metabolism and amylase gene number in human evolution.
The ability both to digest dietary poly/disaccharides and to absorb monosaccharides is critically important. Moreover, it is crucial to control carbohydrate metabolism and maintain circulating concentrations of glucose in animals as much as in people. During human evolution, there has been the acquisition of multiple copies of amylase gene (AMY1). This presumably allows greater utilization of starch (earlier work reviewed [
It has recently been suggested that the ability to thrive on a diet rich in starch was a key feature in the early domestication of dogs. There are signals of selection being reported in ten genes related to starch digestion and fat metabolism in dogs [
There is a large but diffuse literature containing data on serum biochemistry and hematological parameters of wild animals, most commonly determined on blood samples obtained at capture. A database of basal plasma/ serum glucose concentrations in vertebrate species was assembled based on the literature to allow analysis of putative physiological shifts with evolutionary/taxonomic status, ecological parameters and other environmental factors. Circulating concentrations of glucose would be expected to exhibit marked differences e.g. between fed and fasted in mono-gastric omnivorous animals. However, domestic animals and the descendants of their ance- stral wild species are predominantly either ancestrally carnivores or either rumen or hind gut fermenters relying on gluconeogenesis. Circulating concentrations of glucose is widely reported as a serum/plasma biochemical parameter in wild mammals following capture.
On causal inspection of the database, there appeared to be a relationship between domestication and serum/ plasma concentration of glucose with lower levels in domesticated species. The data base was then queried sys- tematically to determine whether circulating concentrations of glucose are different in domesticated species compared to either descendant of the ancestral species or to the taxonomic sub-family or family which the do- mesticated species belongs.
Comparisons between circulating concentrations of glucose in domesticated species and descendants of the same (or very closely related) species or the mean for the sub-family [and where there is available data on insufficient numbers of species (n < 3)―the family] were analyzed by both Student’s paired t test and by split plot analysis of variance (ANOVA) followed by Tukey’s range test.
There was a marked difference (p < 0.001) in the circulating concentrations of glucose between domesticated
Domesticated species | Wild ancestral or closely related species | Serum/plasma glucose (m∙Moles∙L−1) | Reference |
---|---|---|---|
Alpaca (Vicugna pacos) | 6.4 | [ | |
Vicuñas (Vicugna vicugna) | 9.1 | [ | |
Cat (Felis silvestris) | 8.1 | [ | |
European Wildcat (Felis silvestris) | 9.3 | [ | |
Dog (Canis lupo familiaris)* | 3.4 | [ | |
Grey wolf (Canis lupo) | 6.6 | [ | |
Ferret (Mustela putorius furo) | 5.8 | [ | |
European Polecat (Mustela putorius) | 9.3 | [ | |
Horse (Equus ferus) | 5.6 | [ | |
Przewalski horse (Equus przewalskiprzewalski)‡ | 7.2 | [ | |
Llama (Lama glama) | 5.5 | [ | |
Guanaco (Lama guanicoe) | 7.6 | [ | |
Pig (Sus scrofa domestica)† | 5.3 | [ | |
European Wild Boar (Sus scrofa) | 9.3 | [ | |
Reindeer (Rangifer tarandus) | 4.0 | [ | |
Caribou (Rangifer tarandus caribou) | 8.3 | [ |
*Compared to 3.1 m∙Moles∙L−1 in stray dogs [
animals and wild species in the taxonomic sub-families Bovinae and Caprinae in the Family Bovidae (
Circulating concentrations of glucose were consistently lower in domesticated animals than in either matched ancestral species/closely related wild mammalian species (
・ Nutrition―i.e. whether the domesticated species was a ruminant, hind gut fermenter (horse, ass and rabbit) or predominantly carnivore (dog, ferret).
・ Classification/evolutionary relationships―being observed in species from the Orders―Actiodactyla (bovids, camelids, deer and pigs), Carnivora (dogs, ferrets), Lagomorpha (rabbits) and Perissodactyla (horses and donkeys).
Genomic studies in dogs and horses support a shift in carbohydrate metabolism in domesticated species with increasing consumption of starch. The ability to thrive on a diet rich in starch was a key feature in the early do- mestication of dogs. Signals of selection have been reported in ten genes related to starch digestion and meta- bolism in dogs [
The present communication would support it being the selection associated with domestication itself rather than subsequently being response for the difference in circulating concentrations of glucose. There was not a re- lationship (r2 < 0.2; p > 0.45) between the duration of time since domestication and the differences in circulating concentrations of glucose between domesticated animals and either closely related wild species or the mean for the sub-family/family (data not shown).
While the domestic cat is considered within the domestic animals, it can be argued that cats should be consi-
Domesticated Species | Wild Species in Same Taxonomic Group | Serum/Plasma Glucose (m∙Moles∙L−1) | Reference |
---|---|---|---|
Cattle (Bos primigenius formerly Bos taurus)a | 5.2 | [ | |
Gayal-Domesticated Gaur (Bos gaurus) | 2.7 | [ | |
Water Buffalo (Bubalus bubalis) | 3.2 | [ | |
Non-Domesticated-Subfamily Bovinae‡ | 8.0 ± (8) 0.6 | ||
Sheep (Ovis aries) | 4.1 | [ | |
Goat (Capra aegagrus hircus) | 4.2 | [ | |
Non-Domesticated-Subfamily Caprinae‡ | 9.4 ± (6) 0.7 | ||
Alpaca (Vicugna pacos) | 6.4 | [ | |
Camel (Camelus dromedaries) | 4.1 | [ | |
Llama (Lama glama) | 5.5 | [ | |
Non-Domesticated-Family Camelidae‡ | 8.3 ± (2) 0.8 | ||
Pig (Sus scrofa domestica) | 5.3 | [ | |
Non-Domesticated-Family Suidae‡ | 6.1 ± (4) 1.14 | ||
Reindeer (Rangifer tarandus) | 4.0 | [ | |
Non-Domesticated-Family Cervidae‡ | 7.9 ± (14) 0.5 | ||
Dog (Canis lupo familiaris) | 3.4 | [ | |
Non-Domesticated-Subfamily Caninae‡ | 7.1 ± (11) 0.8 | ||
Cat (Felis silvestris) | 8.1 | [ | |
Non-Domesticated Subfamily Felinae‡ | 7.6 ± (11) 0.8 | ||
Ferret (Mustela putorius furo) | 5.8 | [ | |
Non-Domesticated Subfamily Mustelinae‡ | 9.5 | ||
Donkey or Ass (Equus africanus asinus) | 4.1 | [ | |
Horse (Equus ferus) | 5.6 | [ | |
Non-Domesticated-Family Equidae‡ | 7.6 ± (5) 0.6 | ||
Rabbit (Oryctolagus cuniculus) | 6.8 | [ | |
Non-Domesticated-Family Leporidae‡ | 10.2 ± (4) 1.6 | ||
‡Data on wild animal in the same taxa on the domesticated animals is shown as mean ± (n = number of species) S.E.M. |
dered as commensal rather than domesticated [
It might be argued that the greater circulating concentration of glucose in wild species is an artifact of their capture, environment or nutritional state. This does not appear to be the case. Similar concentrations of glucose are reported in captive wolves and those in the wild [
It might be questioned as to whether the lower concentration of glucose in domestic animals reflects an effect of human activity. One way to address this is comparison of glucose in domesticated animals that have reverted
Serum/Plasma Glucose (m∙Moles∙L−1) | |||
---|---|---|---|
I. Comparison between domesticated animals and wild species in the Bovidae subfamilies Bovinae and Caprinae | |||
Domesticated species∆ | 3.9 ± (5) 0.53a | ||
Wild species | 8.6 ± (14) 0.50b | ||
II. Comparison between domesticated animals and matched ancestral or closely related wild mammalian species∆ | |||
Domesticated species | 5.5 ± (8) 0.51a | ||
Ancestral or closely related wild species | 8.3 ± (8) 0.38b | ||
III. Comparison between domesticated animals and mean for wild species within same family or subfamily† | |||
Domesticated species∆ | 4.9 ± (16) 0.36a | ||
Matched family or sub-family wild species | 8.2 ± (16) 0.25b | ||
∆Data shown in
to the wild. Circulating concentrations of glucose in feral adult horses, stray dogs and feral goats are the same as in domesticated animals [
The present study provides evidence that domesticated animals have reduced circulating concentrations of glucose. What is not known include the following: Do the differences in circulating concentrations of glucose reflect amylase gene number as in humans [
The helpful discussions with colleagues, and particularly with Dr. Selvakumar Ramakrishnan, are gratefully ac- knowledged.