A possible explanation is that the abdominal support provided by these two muscles might continue to expand in response to continued visceral growth. The requirement for locomotion immediately after birth may be responsible for an early prenatal acceleration of growth in these muscles, so that subsequent postnatal growth is slower than in the remaining more proximal muscles. Since many of the distal limb muscles have a complex pennate structure , constraints resulting from muscle structure might also be involved. Pennate muscles are restricted in their potential for growth, whereas overlying muscles that are composed of relays of intrafascicularly terminating fibers are able to grow radially and longitudinally for a longer period. This might be a relic of the heavy head and neck muscles that wild bulls once used for fighting.
Rams also show considerable growth of their neck muscles.
Since many of the ventral neck muscles act as antagonists to the ligamentum nuchae, it is possible that this is an ontogenetic, rather than a phylogenetic feature. The growth of the skull and the ligamentum nuchae are probably interrelated so that the enlargement of ventral neck muscles is required to counterbalance a stronger ligamentum nuchae. The distribution of the carcass muscle mass is changed when steers lose weight on a low plane of nutrition. Pigs Pietrain pigs may have greater muscularity in the loin and hindlimb, while Large Whites have relatively greater development of neck, shoulder and forelimb muscles. These two breeds do not differ in bone distribution.