Fig. 2.

Theoretical competitive broken-line response of a random zinc status parameter to changes in dietary zinc (Zn) concentration from 2 different supplemental Zn species. In this example, the parameter (e.g., apparently digested feed Zn) exhibits a plateau in response above dietary thresholds of 60 and 50 mg Zn/kg diet when feeding Zn species A (black) and B (grey), respectively. Below the respective threshold, parameter response to changes in dietary Zn concentration from species A and B decreases or increases by 0.17 and 0.26/mg reduction or rise in dietary Zn, respectively. In conclusion, feeding Zn species B results in a decreased gross Zn requirement (−10 mg Zn/kg diet). Based on the slope comparison, feed Zn species B provided a 1.5-fold higher feed Zn utilization compared with species A based on the relative differences of the respective slopes in response.