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Effects of different levels of crude protein and protease on nitrogen utilization, nutrient digestibility, and growth performance in growing pigs

  • Kim, Yong Ju1
  • Kim, Tae Heon1
  • Song, Min Ho2
  • An, Ji Seon1
  • Yun, Won1
  • Lee, Ji Hwan1
  • Oh, Han Jin1
  • Lee, Jun Soeng1
  • Kim, Gok Mi3
  • Kim, Hyeun Bum4
  • Cho, Jin Ho1
  • 1 Division of Food and Animal Science, Chungbuk National University, Cheongju 28644, Korea
  • 2 Department of Animal Science and Biotechnology, Chungnam National University, Daejeon 34134, Korea
  • 3 Department of Beauty Art, Yonam College, Cheonan 31005, Korea
  • 4 Department of Animal Resource and Science, Dankook University, Cheonan 31116, Korea
Published Article
Journal of Animal Science and Technology
Korean Society of Animal Sciences and Technology
Publication Date
Sep 30, 2020
DOI: 10.5187/jast.2020.62.5.659
PMID: 33089231
PMCID: PMC7553848
PubMed Central


This study was conducted to evaluate the effects of different levels of crude protein (CP) and protease on nitrogen (N) utilization, nutrient digestibility, and growth performance in growing pigs. A total of six crossbred ([Landrace × Yorkshire] × Duroc) barrows were individually accepted in 1.2 m × 0.7 m × 0.96 m stainless steel metabolism cages. The pigs (average initial body weight of 27.91 ± 1.84 kg) randomly assigned to six diets with six weeks (6 × 6 Latin square design). The experiment was carried out in an environment with a temperature of 23 ± 1.5°C, a relative humidity of 83 ± 2.3% and a wind speed of 0.25 ± 0.03 m/s. The dietary treatments were arranged in a 2 × 3 factorial design with two levels of CP (15.3% or 17.1%) and three levels of protease (0 ppm, 150 ppm, or 300 ppm). The average daily gain and gain to feed ratio (G:F) tended to increase ( p = 0.074) with increasing amounts of protease. The low CP level diet reduced ( p < 0.050) urinary and fecal N concentrations, the total N excretion in feces, and increased ( p < 0.050) N retention. Different protease levels in the diet did not affect ( p > 0.05) at N intake, but supplementation of the diets with 300 ppm protease decreased ( p < 0.050) the N concentration in urine and feces and tended to increase ( p = 0.061) the percentage of N retention retained of the total N intake. The dietary CP level did not affect ( p > 0.050) the apparent total tract digestibility (ATTD) of dry matter, digestible energy (DE), and metabolic energy (ME), but diet supplementation with 300 ppm protease showed higher ( p < 0.050) ATTD of DE and ME than in the protease-free diet. Therefore, a low protein diet with protease could improve the utilization of nitrogen, thereby reducing the negative effect of N excretion into the environment while maintaining or increasing growth performance compared to a high protein diet.

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