Kautilya's Arthashastra 2.30.27

2.30.27

yuddhavyādhijarākarmakṣīṇāḥ piṇḍagocarikāḥ syuḥ //02.30.28/ asamaraprayogyāḥ paurajānapadānām arthena vṛṣā vaḍavāsv āyojyāḥ //

Stallions which are incapacitated owing to old age, disease or hardships of war, and, being therefore rendered unfit for use in war live only to consume food shall in the interests of citizens and country people be allowed to cross steeds.