RESUMEN
Two experiments were conducted to determine the effects of Mn source and level on finishing pig growth performance and carcass characteristics. Dietary treatments were arranged in a 2 × 3 factorial with main effects of Mn source (MnSO4; Eurochem, Veracruz, Mexico, or Mn hydroxychloride (IBM); Micronutrients, Indianapolis, IN) and increasing added Mn (8, 16, and 32 mg/kg of complete diet). The trace mineral premix was formulated without added Mn. Copper was added to all diets at 10 and 150 mg/kg in Exp. 1 and 2, respectively. In both experiments, 1,994 pigs (PIC; 337 × 1050; initially 34.5 ± 0.50 and 40.0 ± 0.77 kg) were used with 27 pigs per pen and 12 replicates per treatment. Diets were corn-soybean meal-distillers dried grains with solubles-based and were fed in four phases. In Exp. 1, there was a marginal Mn source × level interaction (quadratic, Ρ = 0.057) for overall feed efficiency (G:F), with a decrease then increase in pigs fed IBM, but G:F increased with increasing Mn from MnSO4. There was no evidence for Mn source differences for average daily gain (ADG), average daily feed intake (ADFI), or body weight (BW), but pigs fed 16 mg/kg Mn, regardless of source, tended to have decreased (quadratic, Ρ < 0.05) ADG and final BW compared with other levels. For carcass yield, there was a tendency for Mn source × level interaction (quadratic, Ρ = 0.075), where carcass yield did not change by increasing MnSO4 but was greatest for 16 mg/kg Mn from IBM. Loin depth increased (source × level, Ρ = 0.041) for pigs fed increasing Mn from MnSO4 but decreased when Mn was increased from IBM. Pigs fed the intermediate level of Mn tended to have the lightest HCW (quadratic, Ρ = 0.071) and decreased loin depth (quadratic, Ρ = 0.044). Liver Mn concentration increased (linear, Ρ = 0.015) as added Mn increased and tended to be greater (P = 0.075) when supplied by MnSO4 compared with IBM. In Exp. 2, there was no (P > 0.10) Mn source × level interaction observed for ADG, ADFI, and G:F. Pigs fed IBM had increased (P < 0.05) final BW, ADG, and ADFI compared with pigs fed MnSO4. Pigs fed 16 mg/kg of Mn tended (P = 0.088) to have reduced ADFI when compared with pigs fed 8 and 32 mg/kg of Mn. In conclusion, there appears to be little benefit in growth performance by feeding more than 8 mg/kg of added Mn. When high levels of Cu were fed in Exp. 2, pigs fed IBM had improved growth performance when compared with those fed MnSO4. Further research is needed to understand the potential benefits of Mn hydroxychloride fed in conjunction with high levels of Cu on pig growth performance.
RESUMEN
Based on results of a recent meta-analysis, we hypothesized that increased dietary Val, Ile, or Trp could correct possible amino acid interactions because of excess Leu in diets containing high levels of corn protein, namely dried distiller's grains with solubles (DDGS). A total of 1,200 pigs (PIC TR4 × (Fast LW × PIC L02); initially 33.6 ± 0.6 kg) were used in a 103-d study. The 6 dietary treatments were corn-soybean meal (SBM)-DDGS-based as follows: (1) high SBM and low level of l-Lys HCl (HSBM), (2) high l-Lys HCl and moderate Ile, Val, Trp (AA above NRC 2012 estimates; NC), (3) moderate l-Lys HCl and high Ile, Val, and Trp (PC), and PC with either increased (4) L-Val (PC+Val), (5) L-Ile (PC+Ile), or (6) L-Trp (PC+Trp). Pigs fed the NC diet were predicted to have the poorest average daily gain (ADG), the PC diet to be intermediate, and pigs fed the HSBM, PC+Val, PC+Ile, and PC+Trp have the same and highest predicted ADG. In the grower period (34 to 90 kg), ADG was greater (Ρ < 0.05) for the pigs fed HSBM and PC+Val diets than the NC with pigs fed other diets intermediate. Pigs fed HSBM were more (Ρ < 0.05) efficient (G:F) than the NC and PC with pigs fed other diets intermediate. In the finisher period (90 to 136 kg), ADG was greater (Ρ < 0.05) for pigs fed PC+Ile than that of the NC with pigs fed other diets intermediate. Pigs fed PC+Val had greater (Ρ < 0.05) average daily feed intake (ADFI) than the NC with pigs fed other diets intermediate. However, PC+Ile pigs were more (Ρ < 0.05) efficient than PC+Val with pigs fed other diets intermediate. Overall, ADG was greater (Ρ < 0.05) for pigs fed HSBM, PC+Val, and PC+Ile diets than the NC with pigs fed other diets intermediate. Pigs fed the PC+Val diet had greater (Ρ < 0.05) ADFI than the NC with pigs fed other diets intermediate. No differences were detected between treatments for overall G:F or other carcass characteristics. In conclusion, increasing Val or Ile in high l-Lys-HCl-DDGS-based diets improved growth performance compared with pigs fed diets containing high levels of l-Lys HCl without added Val and Ile. These results present evidence that the recently developed meta-analysis can predict the relative differences in overall ADG for pigs fed the NC, PC, PC+Val, and PC+Ile diets; however, the predicted G:F was less accurate. The data demonstrate that the negative effects of high Leu concentrations in corn-DDGS-based diets can be reversed by increasing the ratios of Val and Ile relative to Lys.