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Effect of dried distiller grains with solubles (DDGS) feeding strategies on growth and feed intake responses of immunologically castrated pigs harvested at 9, 7 or 5 weeks post-second Improvest dose
Few studies have evaluated growth performance responses when feeding DDGS diets to immunologically castrated pigs. To determine ADG, ADFI, and G:F during the growing-finishing period, entire male pigs (n = 863; initial BW = 21.5 kg) were weighed at 8 weeks of age (WOA), randomly assigned to dietary treatments, and harvested at 9 (TD9), 7 (TD7), or 5 (TD5) weeks post-second dose of Improvest (gonadotropin releasing factor analog - diphtheria toxoid conjugate; Zoetis, Inc., Florham Park, NJ) in a 4 x 3 factorial arrangement (n = 8 pens/ treatment). A 4-phase feeding program (phase 1 = 3 wks, phases 2 and 3 = 4 wks each, and phase 4 = 5 wks) was used for each dietary treatment: positive control (PCon; 0% DDGS in all dietary phases), DDGS step down (SD; 40%, 30%, 20%, and 10% DDGS in the 4 dietary phases, respectively), DDGS withdrawal (WD; 40% DDGS in phases 1 to 3, and 0% DDGS in phase 4), and negative control (NCon; 40% DDGS in all dietary phases). The first subcutaneous Improvest injection was administered at 11 WOA, followed by the second dose at 15, 17, or 19 WOA. All pigs were harvested at 24 WOA. Pig BW and feed disappearance were determined at the beginning and end of each dietary phase, and after 2 weeks in phases 2 to 4. Overall, ADFI tended to be greater (P ≤ 0.10) in WD-TD9 and PCon-TD9 pigs compared with NCon-TD9 pigs (2.44 and 2.45 vs. 2.31 ± 0.08 kg/d). Overall G:F was improved (P ≤ 0.05) in pigs fed PCon and SD compared with pigs fed WD and NCon (0.427 and 0.424 vs. 0.414 and 0.413 ± 0.005). For all TD treatments, ADFI increased (P ≤ 0.05) rapidly post-second Improvest dose, and was greater (P ≤ 0.05) in TD9 compared with TD5 pigs during the 17 to 19 (2.95 vs. 2.48 ± 0.10 kg/d), and during the 19 to 21 (3.25 vs. 2.84 ± 0.10 kg/d) WOA intervals. Overall G:F was improved (P ≤ 0.05) in TD5 pigs compared with TD9 pigs (0.428 vs. 0.413 ± 0.005). Among all TD treatments, G:F was not different between the two-week periods before and after the second Improvest dose. Effects of diet and harvest time post-second dose of Improvest acted independently to influence G:F. Using the SD feeding strategy resulted in similar G:F compared with pigs fed PCon.
Keywords: DDGS, growth, Improvest