Evaluation of trace mineral source and preharvest deletion of trace minerals from finishing diets for pigs on growth performance, carcass characteristics, and pork quality1,2,3

Abstract

Weanling crossbred pigs (Sus scrofa; 72 barrows and 72 gilts; BW = 7.4 ± 1.1 kg) were used to evaluate dietary supplemental trace mineral (Cu, Fe, Mn, and Zn) source (inorganic vs. organic) and deletion (0, 2, 4, and 6 wk preharvest) on growth performance, carcass characteristics, and pork quality. Pigs were blocked by BW, ancestry, and sex, and randomly allotted to 24 pens, and fed a diet containing either inorganic or organic trace minerals supplemented at the 1998 NRC requirement estimates for each of 5 BW phases from 7 to 120 kg (equivalent to 14, 14, 42, 28, and 42-d periods, respectively). Two pigs were removed from each pen at the end of Phase IV (BW = 82.6 ± 6.0 kg), and 2 other pigs were removed at the end of Phase V (BW = 128.0 ± 8.3 kg) for collection of various tissues and for determination of carcass characteristics and pork quality. On d 1, 15, and 29 of Phase V, 3 pens within each source of minerals were switched to a common diet without supplemental trace minerals, whereas the remaining 3 pens within each source of minerals were fed diets containing trace minerals throughout the Phase V period. This resulted in 4 groups within each mineral treatment, in which trace mineral supplementation was deleted for 6, 4, 2, or 0 wk of Phase V. Trace mineral source (inorganic vs. organic) did not affect ADG, ADFI, and G:F (773 vs. 778 g/d, 1,680 vs. 1,708 g/d, and 461 vs. 456 g/kg, respectively) during the first 4 phases. During the mineral deletion period, ADG and G:F were not affected by the duration of trace mineral deletion, but ADFI increased when trace minerals were removed from the diet for 6 wk (6 vs. 0 wk, 3,393 vs. 3,163 g/d; P = 0.05). Hot carcass weight, cold carcass weight, carcass shrink, dressing percentage, LM area, 10th rib and midline average backfat, and carcass fat-free lean weight and percentage were not affected (P > 0.10) by the source of mineral or length of mineral deletion, but carcass length tended to decrease (P = 0.09) when time of trace mineral deletion increased. Increasing mineral deletion from 0 to 6 wk tended to reduce linearly (P = 0.08) Hunter a* scores on the day of carcass processing (24 h after slaughter), as well as 2 d after processing, and Hunter b* scores on d 2 and d 6 after processing. Results of this experiment indicate that use of organic trace minerals, rather than inorganic trace minerals, did not influence pig growth performance or carcass characteristics and quality; however, deletion of minerals during the last 6 wk before harvest increased ADFI and affected drip loss, some color scores of the LM, and carcass length.