Changes

==Species Differences in the Ability To Conserve Water==

==Species Differences in the Ability To Conserve Water==

Mammals and birds can produce urine both more and less concentrated than plasma in order to conserve or excrete water.  The excretion is done without interfering with the levels of solute excretion.  The ability to concentrate urine depends greatly on a species access to water.  Animals with access to lots of water have less of a need and therefore have not evolved great mechanisms to concentrate urine for example the beaver.  However animals who have limited access to water and say live in more arid environments have evolved very good mechanisms to reabsorb lots of water and produce a very concentrated urine. An example of this is the kangaroo rat which lives in a desert habitat.

Mammals and birds can produce urine both more and less concentrated than plasma in order to conserve or excrete water.  The excretion is done without interfering with the levels of solute excretion.  The ability to concentrate urine depends greatly on a species access to water.  Animals with access to lots of water have less of a need and therefore have not evolved great mechanisms to concentrate urine for example the beaver.  However animals who have limited access to water and say live in more arid environments have evolved very good mechanisms to reabsorb lots of water and produce a very concentrated urine. An example of this is the kangaroo rat which lives in a desert habitat.

The following table shows a comparison between the maximum concentrating abilities of the kidneys of various mammals.  Data from Physiology of Domestic Animals - Sjaastad, Hove and Sand.  For full text reference see the [[Acknowledgements Urinary Anatomy & Physiology| Reference Material]]  section.

The following table shows a comparison between the maximum concentrating abilities of the kidneys of various mammals.  Data from Physiology of Domestic Animals - Sjaastad, Hove and Sand.   

Although they have a smaller surface area to body mass ratio than sheep they lose water more quickly through the faeces and the urine when ambient temperature is high.  They also have a far less developed coat.  Indian Cattle (''Bos Indicus'') such as the Brahman and Zebu are better able to tolerate high temperatures than European cattle but only when water is readily available as their increased tolerance comes from an increased sweating ability which would be of no advantage if water was short.  This dependence on water is obvious when you look at behaviour.  Cattle will not willingly roam more than 1 day from water where as sheep and camels will move 3 and 6 days away respectively.

Although they have a smaller surface area to body mass ratio than sheep they lose water more quickly through the faeces and the urine when ambient temperature is high.  They also have a far less developed coat.  Indian Cattle (''Bos Indicus'') such as the Brahman and Zebu are better able to tolerate high temperatures than European cattle but only when water is readily available as their increased tolerance comes from an increased sweating ability which would be of no advantage if water was short.  This dependence on water is obvious when you look at behaviour.  Cattle will not willingly roam more than 1 day from water where as sheep and camels will move 3 and 6 days away respectively.

[[Category:Water Balance and Homeostasis]]

[[Category:Water Balance and Homeostasis]]