Determination of optimal energy system and level for growing pigs

Sangwoo Park1, Jeehwan Choe2, Jinho Cho3, Ki Beom Jang4, Hyunjin Kyoung5, Kyeong Il Park5, Yonghee Kim5, Jinmu Ahn5, Hyeun Bum Kim6,*, Minho Song5,**
Author Information & Copyright
1Department of Animal Science, University of California, Davis 95616, United States.
2Department of Livestock, Korea National University of Agriculture and Fisheries, Jeonju 54874, Korea.
3Department of Animal Science, Chungbuk National University, Cheongju 28644, Korea.
4Department of Animal Science, North Carolina State University, Raleigh 2769, United States.
5Division of Animal and Dairy Science, Chungnam National University, Daejeon 34134, Korea.
6Department of Animal Resources Science, Dankook University, Cheonan 31116, Korea.
*Corresponding Author: Hyeun Bum Kim, Department of Animal Resources Science, Dankook University, Cheonan 31116, Korea, Republic of. E-mail:
**Corresponding Author: Minho Song, Division of Animal and Dairy Science, Chungnam National University, Daejeon 34134, Korea, Republic of. E-mail:

© Copyright 2023 Korean Society of Animal Science and Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.


This study mainly evaluated the responses in growth performance of growing pigs to different energy systems and energy levels in diets. Subsequently, we compared the nutrient digestibility and digestible nutrient concentrations of each energy level diet. In experiment 1, a total of 144 growing pigs with an average initial body weight of 26.69 ± 7.39 kg were randomly allotted to six dietary treatments (four pigs/pen; six replicates/treatment) according to a 2 × 3 factorial arrangement resulting from two energy systems (metabolizable energy [ME] and net energy [NE]) and three energy levels (low [LE], recommended [C], and high energy [HE]). Pigs were fed the experimental diets for 6 weeks and were allowed free access to feed and water during the experimental period. In experiment 2, 12 growing pigs with an average initial body weight of 27.0 ± 1.8 kg were randomly allotted to individual metabolism crates and fed the six diets in a replicated 6 × 6 Latin square design. The six dietary treatments were identical to those used in the growth trial. Pigs were fed their respective diets at 2.5 times the estimated energy requirement for maintenance per day, and this was divided into two equal meals provided twice per day during the experimental period. Differences in energy systems and energy levels had no significant effect on the growth performance or nutrient digestibility (except AEE) of growing pigs in the current study. However, the digestible concentrations of ether extract, acid-hydrolyzed ether extract, and acid detergent fiber (g/kg dry matter [DM]) in diets significantly increased (<italic>p</italic> &lt; 0.05) with increasing energy levels. Additionally, there was a tendency (<italic>p</italic> = 0.09) for an increase in the digestible crude protein content (g/kg DM) as the energy content of the diet increased. Consequently, differences in energy systems and levels did not affect the body weight, average daily gain, and average daily feed intake of growing pigs. This implies that a higher variation in dietary energy levels may be required to significantly affect growth performance and nutrient digestibility when considering digestible nutrient concentrations.

Keywords: Energy system; Net energy; Energy level; Energy concentration; Metabolic response; Growing pigs