How does reducing dietary net energy impact growth performance and carcass characteristics of grow-finish pigs?
“The effect of increasing dietary energy content on performance has been extensively studied,” Rafe Royall, a PhD student in swine nutrition at Kansas State University, explained at KSU Swine Day. “However, as we think about dramatic reductions on net energy, there’s relatively little published data. Elevated ingredient costs have led the industry to shift toward using more high-fiber, low energy diets.”
Kansas State University conducted a study to evaluate the effect of dietary net energy (NE) on growth performance, carcass characteristics, and removal and mortality rates of grow-finish pigs and compare different net energy (NE) systems by using caloric efficiency.
How Did the Study Work?
A total of 1,927 pigs (initially 51.5 ± 0.52 lb) were used in a 125-day study. Pens of pigs were blocked by body weight and randomly allotted to one of five dietary treatments of decreasing NE. Each pen had 23 to 26 pigs and 15 replications per treatment in a randomized complete block design.
The highest NE diet (control) was a corn-soybean meal based diet. Based on NRC (2012) ingredient NE values, the lowest energy diet contained 8% less NE than the control through inclusion of 25% wheat middlings and 15% DDGS (6% oil). These diets were blended to achieve intermediate NE levels (2, 4, and 6% less NE than the control). Dietary phases were fed from approximately 50 to 90, 90 to 130, 130 to 180, 180 to 230, and 230 to 300 lb., respectively.
What Did Researchers Discover?
Overall, reducing NE decreased average daily gain and final body weight, but increased average daily feed intake, resulting in poorer feed efficiency. Reducing NE worsened caloric efficiency (CE) based on NRC ingredient loading values, improved CE based on INRA (2008) or Brazilian Tables for Poultry and Swine (2017) ingredient loading values.
“However, when formulating diets using CVB (2020) ingredient loading values, reducing NE resulted in no evidence of difference in CE,” Royall said. “For carcass characteristics, reducing NE decreased hot carcass weight, backfat depth, and carcass yield. However, reducing NE increased percentage lean.”
In addition, reducing NE tended to increase percent removals, with no evidence of difference on percent mortality.
“When considering CE on a carcass gain basis, reducing NE worsened CE based on NRC or CVB ingredient loading values, while reducing NE improved CE based on INRA ingredient loading values,” Royal said. “However, reducing NE resulted in no evidence of difference in CE based on Brazilian Tables ingredient loading values.”
Royall said these results suggest that the NRC database overestimates NE contributions of fibrous ingredients such as wheat middlings and corn DDGS, while the INRA database underestimates their contributions to NE, whether CE is calculated based on live or carcass gain.
“NE values in the CVB database appear to value NE more accurately in these diets based on live gain but underestimate their value on a carcass basis,” he said. “The Brazilian tables appear to underestimate the contributions of fibrous ingredients to dietary NE on a live basis, but more accurately value their contributions on a carcass basis.”
This study reinforces establishing and utilizing accurate energy values of ingredients to economically value them appropriately.
The study, “Effects of Reducing Dietary Net Energy on Growth Performance and Carcass Characteristics of Grow-Finish Pigs,” is published in Kansas Agricultural Experiment Station Research Reports: Vol. 10: Iss. 6. https://doi.org/10.4148/2378-5977.8641. Researchers include Royall, Rafe Q.; Tokach, Mike D.; Woodworth, Jason C.; DeRouchey, Joel M.; Goodband, Robert D.; Gebhardt, Jordan T.; Vier, Carine M.; Spindler, Matthew; Orlando, Uislei; Zaragoza, Luis; Lu, Ning; Cast, Wayne; Wilson-Wells, Danielle F.; Holen, Julia P.; and Betlach, Alyssa M.
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