Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2009
Publication Date: 4/9/2009
Citation: Veum, T.L., Ledoux, D.R., Shannon, M.C., Raboy, V. 2009. Effect of graded levels of iron, zinc, and copper supplementation in diets with low-phytate or normal barley on growth performance, bone characteristics, hematocrit volume, and zinc and copper balance of young swine. Journal of Animal Science. 87:2625-2634 Interpretive Summary: Seed-derived phytic acid is the major form of phosphorus in feeds but is not well digested or utilized by monogastric animals such as pigs, chickens and fish. In addition, seed-derived feed phytic acid reduces the absorption and utilization of nutritionally important minerals such as iron, zinc and copper. With the development of low-phytate cultivars, it may be possible to reduce the amount of iron, zinc and calcium in feeds necessary to provide for optimal animal growth. In this study young pigs were fed diets prepared from “normal phytic acid” barley and a low-phytic acid barley, M955, in which seed phytic acid is reduced by 90%. In addition, varying levels of iron, zinc and copper were provided to test if animals consuming the M955 barley performed as well with diets with reduced minerals. The results indicated that growth and performance improved with increasing levels of minerals regardless of the type of barley used. Therefore it is recommended that the producers follow the National Research Council’s recommendations for trace mineral supplementation.
Technical Abstract: Fifty crossbred barrows with an average initial age of 31 d and BW of 9.94 kg 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 Harrington 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. Available P was equalized at 0.33% in all diets by adding monosodium phosphate to the basal diet containing NB, and all diets contained 0.65% Ca. Diets were adequate in all other nutrients. 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 x TM treatment interactions, and 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 ADFI, ADG, hematocrit volume, metacarpal bone breaking strength and ash weight, and the apparent absorption, retention, and excretion (mg/d) of Zn and Cu. In conclusion, the LPA barley had no effect on the response criteria in this experiment, apparently because of the small increase in the availability of the endogenous trace minerals in the practical diets containing M955 compared with NB. However, increasing the supplementation of Fe and Zn from 0 to 100% (160% for Cu) of the requirement resulted in linear increases in growth performance, hematocrit volume, metacarpal bone strength and ash weight, and the apparent absorption, retention, and excretion of Zn and Cu. Therefore, these results indicate that the inorganic trace mineral supplementation of practical diets for young pigs should not be less than the National Research Council requirements for swine.