When the angle from the hooks to the pins increases beyond the ideal ~20-25 degrees it causes problems. It introduces unsound structure in the hind legs. The cow will walk under herself with her legs angled too far ahead. She will have difficulty moving at speed or on a slope. It also forces the udder lower to the ground and may additionally reduce udder attachments.
A good length between the pins and hooks and a wide rump will permit a cow to have a calf of reasonable size. At least 7% of her body weight and typically more.
In show cattle, the term level may be misleading here. The slope from the hook to the pin should not be flat, but the tailhead to the hooks should be.
