Mr X should be considered as occupying third trophic level, i.e., secondary consumer.
Producer (grass) - First trophic level
Primary consumer (cow) - Second trophic level
Secondary consumer (man) - Third trophic level
Here cow is eating grass (1st level), grass transfers energy to the cow (2nd level). The cow is producing milk from which curd is prepared. The person, Mr X (3rd level) is eating the curd. This means the energy is getting transferred from cow to man through curd (byproduct of cow).

──────────────────────────────────────────────────────────────────────────────────────────