Mahārāja Yudhiṣṭhira had to collect heaps of gold to secure the paraphernalia for the horse sacrifice yajñas in days of sufficiency, so we can hardly think of such performance of yajñas in these days of insufficiency and complete scarcity of gold. At the present moment we have heaps of papers and promises of their being converted into gold by economic development of modern civilization, and still there is no possibility of spending riches like Mahārāja Yudhiṣṭhira, either individually or collectively or by state patronization. Just suitable, therefore, for the age, is the method recommended by Lord Śrī Caitanya Mahāprabhu in terms of the śāstra. Such a method requires no expenditure at all and yet can award more benefit than other expensive methods of yajña performances.
The horse sacrifice yajña or cow sacrifice yajña performed by the Vedic regulations shouldn't be misunderstood as a process of killing animals. On the contrary, animals offered for the yajña were rejuvenated to a new span of life by the transcendental power of chanting the Vedic hymns, which, if properly chanted, are different from what is understood by the common layman. The Veda-mantras are all practical, and the proof is rejuvenation of the sacrificed animal.
There is no possibility of such methodical chanting of the Vedic hymns by the so-called brāhmaṇas or priests of the present age. The untrained descendants of the twice-born families are no more like their forefathers, and thus they are counted amongst the śūdras, or once-born men. The once-born man is unfit to chant the Vedic hymns, and therefore there is no practical utility of chanting the original hymns.
And to save them all, Lord Śrī Caitanya Mahāprabhu propounded the saṅkīrtana movement or yajña for all practical purposes, and the people of the present age are strongly recommended to follow this sure and recognized path.