0
Fifty crossbred barrows with an average initial age of 31 d were used in a 28-d experiment to evaluate the effect of a low-phytic acid (LPA) barley mutant (M) M955, a near-isogenic progeny of the normal barley (NB) cultivar with about 90% less phytate than NB, to increase the utilization of Fe, Zn, and Cu compared with diets containing NB. The response criteria were growth performance, hematocrit volume, metacarpal bone characteristics, and the apparent absorption, retention, and excretion of Zn and Cu. The 2 barley cultivars (NB and M955) and the 5 trace mineral (TM) treatment concentrations of Fe and Zn (0, 25, 50, 75, and 100% of the requirement as FeSO4 and ZnSO4) and Cu (0, 40, 80, 120, and 160% of the requirement as CuSO4) made 10 treatments in a factorial arrangement. Barley and soybean meal were the only sources of phytate in the practical diets that also contained spray-dried whey. The barrows were fed the diets to appetite in meal form twice daily in individual metabolism crates.
There were no barley cultivar (NB vs. M955) x TM treatment interactions for any of the response criteria measured in this experiment. Therefore, the main effect means are reported for the 2 barley cultivars and the 5 TM treatments. There were no differences between the NB and M955 barley cultivars for any of the response criteria measured. However, for the TM treatments, there were linear increases (P≤0.05) in overall (0 to 28 d) ADFI and ADG, hematocrit volume on d 13 and 27, metacarpal fresh bone and ash weights, and metacarpal breaking strength with increasing concentration of TM (Fe, Zn, and Cu) treatment. Also, there were TM treatment responses (P≤0.05) for ADFI, ADG, hematocrit volume on d 13 and 27, and bone breaking strength because of the low values for pigs on TM0 compared with pigs on TM50, TM75, or TM100. Also, the concentrations of Zn and Cu in metacarpal bone ash did not differ among the TM treatments. There were no differences between the NB and M955 cultivars for any of the Zn and Cu balance response criteria measured. However, for the TM treatments, there were linear increases in the mg of Zn (P<0.001) and Cu (P≤0.01) absorbed, retained, and excreted in feces and urine daily, and linear increases in the percentages of total (fecal+urinary) Zn and Cu excreted with increasing dietary concentration of TM treatment. Also, there were linear decreases (P<0.001) in the percentages of Zn and Cu that were absorbed and retained with increasing concentration of TM treatment.
It was concluded that increasing the supplementation of Fe and Zn from 0 to 100% (160% for Cu) of the requirement, increases growth performance, hematocrit volume and metacarpal bone strength and ash weight, and the apparent absorption, retention, and excretion of Zn and Cu.
TL Veum, DR Ledoux, MC Shannon and V Raboy. 2009. Journal of Animal Science, 87:2625-2634.
