According to a number of sources , cruelty to animals is an offence and it is punishable in most countries. But in historical film it's inevitable, because if a film is looking to be historically accurate, and hunting animals (for example) was something important to the historical period and in battle sequences.For instance, In Gladiator the horse sequence at the initial battle were worst and of course that's a worst animal abuse sequences.
According to wikipedia,
TV & film making
Animal cruelty has long been an issue with the art form of filmmaking, with even some big-budget Hollywood films receiving criticism for allegedly harmful—and sometimes lethal—treatment of animals during production. One of the most infamous examples of animal cruelty in film was Michael Cimino's legendary flop Heaven's Gate, in which numerous animals were brutalized and even killed during production.
I'm curious to know about,Nowadays, Do the directors follow any techniques to prevent animal cruelty i.e filming with trained animals,faking the slaughter of animals?