the livestock trough 10 of the present invention is generally depicted in fig1 – 4 . the trough 10 is provided with a base 12 having an upper surface 14 and a lower surface 16 . a wall 18 extends upwardly from the peripheral edge portion of the base 12 to form an open cavity 20 . it is contemplated that the base 12 and wall 18 could be formed from nearly any material , so long as the material is suitable for extended periods of contact with water . for example , the trough could be formed from metal , such as the ubiquitous round or ovular metal water troughs that are frequently used for watering livestock . the shape of the trough is relatively unimportant and may be configured to fit any particular application . it is preferred , however , that the trough be sized and shaped to support a sufficient volume of water to support the livestock for which it is intended . in a preferred embodiment , the trough is comprised of a recycled over - the - road tire having one of its sidewalls removed . when positioned in a generally horizontal fashion , the base 12 of the trough will be comprised of the remaining side wall , and the wall 18 will be comprised of the tread . in this position , however , the base will have an inner edge portion that defines a large opening 22 in the base 12 . a plug 24 must be used to seal the opening 22 so that the trough 10 will hold a desirable volume of fluid . it is contemplated that the plug 24 could be comprised of nearly any material , such as rubber , metal or concrete . however , in a preferred embodiment , the plug 24 is comprised of a plastic , such as polyethylene or other similar material . a fluid supply conduit 26 should be positioned in selective fluid communication with the cavity 20 to supply the desired volume of water . it is contemplated that the source of the water could be a neighboring body of water , a well or the like . it is further contemplated that the method of delivering the water through the fluid supply conduit 26 could be one of many known methods , including gravity systems , electric pumps , solar - powered pumps , sling pumps , etc . in a preferred embodiment , the fluid supply conduit 26 extends upwardly through an opening 28 in the plug 24 so that it is positioned at least partially within the cavity 20 . it is contemplated , however , that a similar opening could be formed in virtually any other location in the trough , such as the base 12 or the wall 18 through which the fluid supply conduit 26 could be run . location of the fluid supply conduit 26 through the plug 24 , however , provides a generally centered location for the fluid supply conduit 26 , making it more difficult for the livestock to come into contact with the fluid supply conduit 26 . a valve 30 is coupled to the terminal end of the fluid supply conduit 26 . in a preferred embodiment , a float valve is used , such as the float valves depicted in fig2 – 4 . however , other known valves could be interchanged with the float valve to achieve the desired regulation of water through the fluid supply conduit 26 . a valve actuator 32 , such as the ball float 33 depicted in fig2 – 4 , is coupled with the valve 30 . where circumstances deem prudent , many different types of valve actuators could be incorporated with the valve 30 . for example , a ball float 33 may be coupled to the float valve using a substantially rigid arm member 35 ( fig2 and 3 ) or a substantially flexible cord member , depending on the type of float valve used . to conserve space , a vertically movable float 39 ( fig4 ) can be coupled with the valve 30 and the fluid supply conduit 26 . other actuators , such as electronic moisture sensors and the like , could be incorporated . regardless of the type of actuator 32 or valve 30 used with the system , the principal function of the two will be to regulate the flow of the water from the fluid supply conduit 26 until a desired volume is attained . at that point , the actuator 32 should function to simply close the valve 30 . it is preferred that the actuator be adjustable to alter the volume of fluid within the trough 10 as desired . in a preferred embodiment , an inner wall 34 is coupled to the trough 10 so that it at least partially surrounds the valve 30 and valve actuator 32 , forming a protective tower to further reduce the likelihood of contact between the fluid supply line 26 , the valve 30 , or the valve actuator 32 with the livestock . as depicted in fig3 and 5 , the inner wall 34 is shaped to define an inner chamber 36 , which should be sized and shaped to house the valve 30 and valve actuator 32 accordingly . where desirable , an overflow conduit 41 may be positioned within the inner chamber 26 at a desired height from the base 12 or plug 24 so that the fluid within the cavity 20 will not overflow in the event that the valve 30 and / or valve actuator 32 fail . a removable cap 38 may be removably coupled to the inner wall 34 to further protect the structures positioned within the inner chamber 36 , while permitting access for maintenance . the inner wall 34 should be secured to the plug 24 ( or other structural member from which it will depend ) in a watertight fashion . as depicted in fig2 , 3 and 5 , the inner wall 34 may be secured to a water access cover 40 , which can be fastened to the plug 24 over an optional access hole 45 formed within the plug 24 . the type of fastener 42 used will depend upon the materials selected for the plug 24 . however , in the example of a plastic member , stainless steel screws are an example of one type of appropriate fastener . to further guarantee a watertight seal , an o - ring 43 can be secured between the plug 24 and the water access cover 40 around the access opening 45 . the plug 24 , where a plastic or rubber material is used , can be secured to the base 12 adjacent the opening 22 by first applying a layer of sealant between the plug 24 and the base 12 . the plug 24 can then be fastened to the base 12 using an appropriate fastener , such as the stainless steel screws 44 . however , the type of fastener 44 used may change where the materials for the plug 24 and the base 12 require . to substantially drain the volume of fluid from the cavity 20 , a drain hole 46 should be formed within the base 12 or wall 18 . a drain plug 48 should be provided to adequately seal the drain hole 46 when the trough 10 is in use . press - fit , threadably - mated , and other drain plugs 48 are contemplated . the design of the trough 10 is sufficiently flexible to accommodate additional structures and features . for example , the trough 10 may be supported above ground level by a base , which could be comprised of a second over - the - road tire , to provide an elevated drinking position for the livestock . where a heat sink is desired in colder climates , the trough 10 is easily positioned above a hole in the ground , which is dug deeper than the frost line . one or more heat conduits could be inserted through the base 12 or plug 24 to direct the passage of heat from below the frost line , up through the hole in the ground , and through the heat conduits , forming a heat sink to substantially prevent the fluid within the cavity 20 from freezing . in the drawings and in the specification , there have been set forth preferred embodiments of the invention ; and although specific items are employed , these are used in a generic and descriptive sense only and not for purposes of limitation . changes in the form and proportion of parts , as well as substitution of equivalents , are contemplated as circumstances may suggest or render expedient without departing from the spirit or scope of the invention as further defined in the following claims . thus it can be seen that the invention accomplishes at least all of its stated objectives .