Abstract This experiment evaluated the response of finishing pigs to reduced dietary energy density, achieved either by lowering the inclusion of added fat or by increasing the inclusion of fibrous ingredients. A total of 1,194 crossbred boars and gilts Pietrain × (Landrace × Large White) with an initial body weight (BW) of 75.1 ± 6.87 kg (mean ± SD) were housed in 96 single-sex pens, blocked by BW, and randomly assigned to 4 dietary treatments. Each pen contained 10-13 pigs, with 24 pens per treatment. Pigs were fed the experimental diets for 42 d and individually weighed on d 0, 23 and 42. All diets contained 0.85% SID lysine and 2,421, 2,324, 2,321, and 2,221 kcal net energy (NE), respectively. Energy reduction was achieved by either decreasing added fat from 2.50% to 0.60%, including 20% wheat middlings while maintaining 2.50% fat, or combining 20% wheat middlings with reduced fat inclusion (0.60%). The first 2 diets contained 12.7% neutral detergent fiber, whereas the latter two contained 16.0%. Following the 42-d growth study, pigs were marketed over a 4-wk period, and carcass characteristics were collected. Performance data were analyzed using a linear mixed model including treatment and sex as fixed effects and block as a random effect. Carcass data were analyzed with treatment and sex as fixed effects, hot carcass weight as a covariate, and pen and marketing group as random effects. Increasing added fat, regardless of fiber inclusion, decreased ADFI (2.07 vs. 2.01 kg; P = 0.006). Fiber inclusion reduced daily NE intake (4.85 vs. 4.61 Mcal; P 0.001) and ADG (0.782 vs. 0.752 kg; P = 0.006). FCR increased as dietary energy density decreased (P 0.001), being lowest in diets with added fat and no wheat middlings. Energy conversion ratio decreased with the reduction in dietary energy (P = 0.023). Increasing fiber, regardless of fat inclusion, reduced the digestibility of ash, protein, organic matter, and gross energy (P 0.001). Fat digestibility was highest in the diet containing added fat and no wheat middlings, differing significantly from the other treatments (P 0.001). Final BW and hot carcass weight did not differ among treatments (P = 0.193 and P = 0.109, respectively). However, fiber inclusion tended to reduce carcass yield (P = 0.052), increased carcass leanness (64.3 vs. 64.6%; P = 0.003) and decreased backfat thickness (13.40 vs. 13.02 mm; P = 0.016). Reducing dietary energy by lowering added fat increased feed intake, resulting in similar energy intake and growth performance but a poorer feed efficiency, without affecting carcass characteristics. In contrast, reducing dietary energy by including 20% wheat middlings decreased energy intake and growth rate, worsened feed efficiency, and reduced carcass yield and fat deposition.
Salgado-López et al. (Wed,) studied this question.
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