The Effects of Dietary Net Energy on Growth Performance and Carcass Characteristics of PIC 337 or PIC 800 Sired Grow-finish Pigs

Abstract This study evaluated the effects of dietary net energy (NE) on growth performance, carcass characteristics, and removal and mortality rates of PIC 337 and PIC 800 sired grow-finish pigs. A total of 2,384 pigs (initially 25.5±0.56 kg) were used in a 113-d trial. Mixed sex pens were blocked by BW and randomly allotted to treatments in a randomized complete block design with 23 to 26 pigs/pen and 16 replications/treatment. Treatments were arranged as a 2 × 3 factorial with sire line (PIC 337 or PIC 800) and dietary energy level Low Energy (LowE), Moderate Energy (ModE), and High Energy (HighE) as factors. Diets were formulated to different NE concentrations using Eq. 1-8 NRC (2012) and proximate analysis of the major ingredients. The ModE diet was corn–soybean meal–based, LowE contained 3.2% less NE achieved with 27–30% DDGS (6% oil) inclusion, and HighE contained 3.2% greater NE with 1.65% corn oil. Thus, dietary NE fed through 4 dietary phases were: phase 1 (2,295, 2,371, and 2,447 kcal/kg); phase 2 (2,332, 2,409, and 2,486 kcal/kg); phase 3 (2,363, 2,440, and 2,518); and phase 4 (2,374, 2,452, and 2,530 kcal/kg). Dietary phases were fed from approximately 25-45, 45-73, 73-100, 100-130 kg body weight, respectively. Data were analyzed using mixed models in R, considering pen as the experimental unit for performance traits and individual carcasses for carcass traits. There was no evidence of interaction between sire line and dietary energy levels. Overall, PIC 800 pigs had marginally increased average daily gain (ADG; P = 0.083) and final body weight (P = 0.066) than PIC 337 pigs, whereas PIC 337 pigs consumed less feed (P 0.001) and were more feed efficient (P 0.001; Table 1). PIC 337 pigs had lower hot carcass weight (HCW), but greater loin depth and carcass lean compared to PIC 800 pigs (P 0.001; Table 1). Pigs fed the LowE diet had the lowest ADG, final BW, and HCW, whereas pigs fed the HighE diet had the greatest values, with pigs fed ModE intermediate (P 0.001). Dietary energy level did not affect average daily feed intake (P = 0.311); however, feed efficiency improved as dietary NE increased, with pigs fed LowE being the least efficient, followed by ModE and HighE (P 0.001). Pigs fed the LowE diet also had poorer caloric efficiency and reduced carcass yield, backfat, and loin depth compared with pigs fed ModE and HighE diets. Removal and mortality rates did not differ among sire lines or dietary treatments. In summary, PIC 337 and PIC 800 pigs differed in growth and carcass traits but responded similarly to changes in dietary NE. Reducing dietary NE decreased growth performance and carcass quality in both genetic lines.