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The effects of reduced protein diet supplemented with arginine plus glutamine–glutamate on growth performance, diarrhea incidence, blood metabolites, nutrient digestibility, and nitrogen utilization in nursery pigs |
Lucas Medina Teixeira1 
, Jansller Luiz Genova1
, Fernanda Fialho Abranches1
, Gabriel Cipriano Rocha1,*
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Universidade Federal de Viçosa, Viçosa/MG, Brazil |
Correspondence:
Gabriel Cipriano Rocha, Tel: +55-31-3612-4635, Email: gcrbrazil@gmail.com
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Received: 23 September 2025 • Revised: 12 October 2025 • Accepted: 30 October 2025 |
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| Abstract |
Purpose
This study evaluated the effects of reducing crude protein (CP) and supplementing arginine plus glutamine–glutamate on growth performance, diarrhea incidence, blood metabolites, amino acid profiles, nutrient digestibility, and nitrogen (N) utilization in nursery pigs. Methods: A total of 200 piglets (20 d of age; 4.8±0.58 kg) were allotted to 5 diets in a randomized block design: 22.5, 21.0, 19.5, or 18.0% CP, and 18.0% CP supplemented with 5 g/kg L-arginine and 10 g/kg L-glutamine+glutamate. Pigs were fed in two phases (20–32 and 32–44 d of age) over a 24-d period. Results: Reducing CP linearly decreased average daily gain and worsened feed efficiency, with the lowest performance observed in pigs fed the 18.0% CP diet with arginine and glutamine–glutamate. Serum urea N and gamma-glutamyl transferase increased linearly with CP level. Plasma arginine and ornithine were elevated by supplementation. Methionine, threonine, and valine were highest in pigs fed 18.0% CP diets. In contrast, phenylalanine and tyrosine declined with reduced CP. Diarrhea incidence and fecal scores were greater in pigs fed 22.5% CP, with each 1% CP increase raising diarrhea incidence by 3.55% points. Digestibility of protein and energy improved with increasing CP, and pigs fed 22.5% CP showed the greatest N absorption but also higher fecal N excretion. Conclusion: Collectively, results indicate that reducing CP from 22.5 to 18.0% compromises growth and nutrient digestibility, even when supplemented with arginine and glutamine–glutamate, but lowers diarrhea incidence and N output. These findings highlight trade-offs between growth efficiency, gut health, and environmental sustainability in nursery pig nutrition. |
| Keywords:
Nitrogen utilization; Conditionally essential amino acids; Nutrient digestibility; Protein reduction; Weaned piglets |
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