Abstract
The present study investigated the interactive effects of copper sources and a high level of phytase on growth performance, nutrient digestibility, tissue mineral concentrations, and plasma parameters in nursery pigs. Weaning piglets (N = 192; 6.06 ± 0.99 kg), blocked by body weight, were randomly allotted to 1 of 4 dietary treatments, with 12 pens per treatment and 4 pigs per pen. A basal diet for each phase was formulated to meet nutrient requirements for nursery pigs with the exception that standardized total tract digestibility (STTD) P was reduced by 0.12% and Ca was adjusted to achieve Ca/STTD P = 2.15. The 4 dietary treatments were arranged in a 2 × 2 factorial design, with 2 Cu sources (125 mg/kg Cu from copper methionine hydroxy analogue chelate (Cu-MHAC) or copper sulfate (CuSO4)) and 2 phytase levels (0 or 1500 phytase units (FTU)/kg). Results showed that there was an interaction (P < 0.05) between Cu sources and phytase on ADG during days 0–41. When phytase was not present in the diets (P deficient), there was no difference between the two Cu sources in terms of ADG during days 0–41, whereas with phytase in the diets, Cu-MHAC tended to improve (P < 0.10) ADG during days 0–41 compared with CuSO4. Pigs fed Cu-MHAC had greater apparent total tract digestibility (ATTD) of neutral and acid detergent fiber and STTD of P than those fed CuSO4. Phytase increased (P < 0.05) growth performance, ATTD of Ca and P, and plasma inositol and growth hormone concentrations. In conclusion, Cu-MHAC may be more effective in improving growth rate than CuSO4 when phytase was supplemented at 1500 FTU/kg. Cu-MHAC enhanced fiber and P digestibility regardless of phytase, compared with CuSO4. Phytase addition in P-deficient diets was effective in improving growth performance, Ca and P digestibility, and plasma inositol and growth hormone concentrations.
Highlights
High levels of copper sulfate (CuSO4, 150 to 250 mg/kg Cu) are widely used in nursery pigs to promote growth and improve feed efficiency [1]
When phytase was included in the diets, Cu-MHAC tended to increase (P < 0.10) Average daily gain (ADG) during days 0–41 compared with CuSO4
Studies have demonstrated that Cu-proteinate [5] and Cu-MHAC [6, 7, 9] achieved greater growth performance in nursery pigs than CuSO4 at the same Cu inclusion levels, which was further supported by the current study that Cu-MHAC achieved greater average daily gain than CuSO4 in the presence of phytase supplementation at 1500 FTU/kg
Summary
High levels of copper sulfate (CuSO4, 150 to 250 mg/kg Cu) are widely used in nursery pigs to promote growth and improve feed efficiency [1]. Copper sulfate is dissociated in the acidic pH in the stomach, allowing Cu to interact with phytate and resulting in the formation of Cu-phytate complexes [10, 11] These complexes could impair phytase efficacy, resulting in lower P release from the phytate molecule [11, 12]. Our recent data suggests that Cu-MHAC may enhance phytase efficacy on bone mineralization in nursery pigs when 500 FTU/kg phytase is used, compared with CuSO4 [9]. There is no data on the interaction of copper source and phytase supplementation at high levels on growth performance and mineral digestibility in pigs. It is hypothesized that Cu-MHAC could enhance the efficacy of phytase at 1500 FTU/kg on growth performance
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