"... him getting horny after riding on a horse..."
Is that all there is to it? I mean, is there no underlying message, an attempt at a profound metaphor? shrug
Shaffer was inspired to write his play when he heard of a crime involving a teenage boy's apparently senseless mutilation of horses. He then set out to construct a fictional account of what might have caused the incident, without knowing any of the details of the crime. The play is posted as a postmodern detective story with psychoanalysis and psychotherapy framing the events. (For more on the psychoanalytical aspects of the work, see Little Hans: a case study by Freud.)
At the beginning of the play, 17-year-old Alan Strang is brought to a mental health facility for treatment by psychiatrist Dr. Martin Dysart after he is caught blinding horses with a metal hoof pick at the stables where he worked part-time. In learning to understand Alan and his motivations, Dysart is forced to reexamine the choices he himself has made and the validity of his vocation and to confront his spiritual atrophy, described as the result of a modern consumer culture that tolerates only enervated conformity. Dysart reflects: "That boy has known a passion more ferocious than I have felt in any second of my life. And let me tell you something: I envy it. ... I watch [my wife]...night after night — a woman I haven't kissed in six years — and he stands in the dark for an hour, sucking the sweat off his god's hairy cheek!"
According to Randy Harrison, who starred in the play's latest American revival (2005): "Equus is one of the most significant English-language plays of the past 30 years. Anybody who hasn't seen it or read it needs to, if they care at all about theatre or literature."
Other critics, both when the play debuted in the 1970s and presently, regard the play as pretentious and shallow. Some fault the play for relying too much on shock value over substance and for its gratuitous nudity.
Wikipedia.
I think it sounds interesting, I'd like to see it at some point. I also think a lot of people spend far too much time whining over the fact that it's Daniel Radcliffe - Oh my, not that Harry Potter actor! For shame! - and that there's a scene where he simulates an orgasm involving a horse. Surely there's more to it.