Sportiveness

You will see the tame horse in the paddock gallop about for his pleasure, and the wild horse on the prairie will start and run for miles in mere sportiveness.

Source: wiktionary

Then he would play with his vixen, she encouraging him with her pretty sportiveness.

Source: wiktionary

OMAR KHAYYAM, astronomer-poet of Persia, born at Naishapur, in Khorassan; lived in the later half of the 11th century, and died in the first quarter of the 12th; wrote a collection of poems which breathe an Epicurean spirit, and while they occupy themselves with serious problems of life, do so with careless sportiveness, intent he on the enjoyment of the sensuous pleasures of life, like an easy-going Epicurean.

Source: wiktionary