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Two different experiments were conducted for the present study. In Exp 1, 50 barrows and 48 gilts were initially distributed according to BW and sex and randomly assigned to the experimental treatments. In the Exp 2, 148 early weaned (15-17 d of age) piglets mixed sexes were distributed by sex and initial BW. After 1 wk of adaptation to the nursery diets they were randomly assigned to the experimental treatments. In both experiments the experimental treatments offered to the animals were either the control or the low nutrient excretion diet. Control diets were corn and soybean meal diets containing minimal synthetic amino acid supplementation and no phytase. Low nutrient excretion diets were formulated with low phytic acid corn replacing the control normal corn. Crude protein concentrations were reduced and accompanied by supplementation of synthetic lysine, methionine, threonine, and tryptophan. Phytase was added to the low nutrient excretion diets. Diets were phase fed separately to barrows and gilts, and feed and water were provided ad libitum. Individual BW and pen feed disappearance were measured at 2-wk intervals to determine BW changes, ADG, ADFI and GF. Backfat and longissimus muscle (LM) area was ultrasonically scanned at day 34 of the nursery period and wk 8 and 16 of the grower-finisher period. Ten pigs/ sex/treatment were slaughtered at wk 16 of each experiment to determine carcass characteristics.
Overall growth performance was not different during each experiment. However, nursery G:F (control = 0.65; low nutrient excretion = 0.60), grower ADG (Exp. 1 and 2), and grower G:F (Exp. 2) were reduced (P < 0.05) when the low nutrient excretion diets were fed. Diet had no effect on 10th-rib carcass data in either experiment. Metatarsal bone ash percentage was reduced (P < 0.05) when the low nutrient excretion diets were consumed in both experiments. Feeding low nutrient excretion diets resulted in the maintenance of overall growth performance, bone variables, and carcass characteristics.
It is concluded that further refinements are still required in the nursery and grower phases of pig production to optimize low nutrient excretion diet use by the swine industry.
RB Hinson, AP Schinckel, JS Radcliffe, GL Allee, AL Sutton and BT Richert. 2009, Journal of Animal Science, 87: 1502-1517
