Cǎo character

The phrase reflects mares being pastured for breeding.

The history Records of Wei uses 草馬 (“grass horse”) for mares. In the Tang dynasty, Yan Shigu explained the husbandry: males were stabled for riding and war; mares grazed to breed. The sixth-century dictionary Yupian gives 騲 the broad sense “female livestock”; the rhyme dictionary Guangyun (1008) narrows it to “mare.”

Yan Zhitui’s sixth-century advice book Family Instructions of Master Yan records a regional split in the Classic of Poetry, an early poetry anthology: Jiangnan copies (lower Yangtze) read 牡 (“male”); Hebei copies (northern China) read 牧 (“to graze”).