Not necessarily. Horses are incapable of enjoying such "human" rewards for "work" as futures. Animals do not think of sacrificing the present for the unforeseeable future. Animals do not accumulate for the sake of accumulation. They are not put on the rack of unlimited wants and hence "scarcity" conceived in human terms.
I think that "social construction" business is incapable of producing theory that illuminates the nature of capitalism. Yes, all categories _are_ historically constructed, but it does not mean that _all_ categories are equally invalid. However, "social constructivists" are incapable of offering any ground for distinguishing valid and invalid categories for politically effective analysis.
For instance, what is "work"? In _Grundrisse_, _Capital_, etc., Marx takes pains to point out that one of the most deleterious ideological effects of capitalism is the naturalization of wage labor through the positing of "work" as such, "labor" as such, "production" as such. By positing the natural continuum of "work" as such, capitalism assimilates the past to the present, thereby obscuring what makes the "social order" of capitalism unlike that of any previous social relations. Marx writes in _Grundrisse_:
***** _Production in general_ is an abstraction, but a rational abstraction in so far as it really brings out and fixes the common element and thus saves us repetition. Still, this _general_ category, this common element shifted out by comparison, is itself segmented many times over and splits into different determinations. Some determinations belong to all epochs, others only to a few....[Nevertheless] the elements which are not general and common, must be separated out from the determinations valid for production as such, so that in their unity...their essential differences are not forgotten. The whole profundity of those modern economists who demonstrate the eternity and harmoniousness of the existing social relations lies in this forgetting. For example....[c]apital is, among other things, also an instrument of production, also objectified, past labour. Therefore, capital is a general, eternal relation of nature; that is, if I leave out just the specific quality which alone makes "instrument of production" and "stored-up labour" into capital....
If there is no production in general, there is also no general production. Production is always a _particular_ branch of production...or it is a _totality_....
It is the fashion to preface a work of economics with a general part -- and precisely this part figures under the title "production" (see for example J.S. Mill) -- treating of the _general preconditions_ of all production. This general part consists or is alleged to consist of (1) the conditions without which production is not possible....But, as we will see, this reduces itself in fact to a few very simple characteristics, which are hammered into flat tautologies; (2) the conditions which promote production to a greater or lesser degree....
But none of all this is the economists' real concern in this general part. The aim is, rather, to present production -- see e.g. Mill -- as distinct from distribution etc., as encased in eternal natural laws independent of history, at which opportunity _bourgeois_ relations are then quietly smuggled in as the inviolable natural laws on which society in the abstract is founded. *****
This is the method of the Robinsonades:
***** Smith and Ricardo still stand with both feet on the shoulders of the eighteenth-century prophets, in whose imaginations this eighteenth-century individual -- the product on one side of the dissolution of the feudal forms of society, on the other side of the new forces of production developed since the sixteenth century -- appears as an ideal, whose existence they project into the past. Not as a historic result but as history's point of departure. As the Natural Individual appropriate to their notion of human nature, not arising historically, but posited by nature. (Marx, _Grundrisse_) *****
The "social constructivist" justification for "animal rights" that Wojtek offers naturalizes "work" in the fashion of the Robinsonades. The same goes for Peter Singer's utilitarian justification of "animal rights," except that in his case it is the category of "feelings as such" ("pains and pleasures as such") that does the work of naturalization and assimilation.
In short, while historical materialists agree with "social constructivists" that all social categories are man-made (a simple statement of a fact that is neither here nor there), we differ from them, in that while "social constructivists" are incapable of distinguishing valid from invalid abstractions for political analysis, historical materialists argue that abstractions which assimilate the non-capitalist past to the capitalist present (i.e., ahistorical categories of "work as such," "feelings as such," "natural rights," etc.) are not only anachronistic but also obscurantist.
Yoshie