Effects of dietary rumen undegradable protein:rumen degradable protein ratio on nitrogen metabolism in Hanwoo steers

Kim, Sang Yeob; Bharanidharan, Rajaraman; Im, Seyun; Kim, Kyoung Hoon; Oh, Joonpyo; Kim, Hyun Jin; Lee, Jaesung; Ranaweera, Kamburawala Kankanamge Tharindu Namal; Jeong, Jin Woo; Oh, Jun Seok; Lee, Sang Hyun; Baik, Myunggi

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Anim Biosci > Accepted Articles

Article

https://doi.org/10.5713/ab.24.0592 [Accepted] Published online February 27, 2025.

Effects of dietary rumen undegradable protein:rumen degradable protein ratio on nitrogen metabolism in Hanwoo steers

Sang Yeob Kim¹

, Rajaraman Bharanidharan²

, Kamburawala Kankanamge Tharindu Namal Ranaweera¹

, Jin Woo Jeong¹

, Jun Seok Oh¹

, Sang Hyun Lee¹

, Myunggi Baik^1,*

¹Seoul National University, Seoul, Korea
²Seoul National University, Pyeongchang, Korea
³Cargill Animal Nutrition Korea, Seongnam, Korea

Correspondence: Myunggi Baik, Tel: +82-2-880-4809, Fax: +82-2-872-8583, Email: mgbaik@snu.ac.kr

Received: 23 August 2024 • Revised: 23 September 2024 • Accepted: 5 December 2024

Abstract

Objective
We investigated the effects of dietary rumen undegradable protein (RUP):rumen degradable protein (RDP) ratio on growth performance, nitrogen (N) metabolism, and rumen and blood parameters in Hanwoo (Korean cattle) steers.
Methods
Eight Hanwoo steers (average body weight, 393 kg) were allocated to two groups and fed with a high RUP:RDP ratio (46.9:53.1 based on crude protein) or a low RUP:RDP ratio (30.6:69.4) concentrate with iso-crude protein content in a 2×2 Latin square design in two successive periods.
Results
The high RUP:RDP group had higher (p<0.01) average daily gain, and lower (p<0.05) ruminal ammonia and plasma urea N concentrations than the low RUP:RDP group. The high RUP:RDP group had lower (p<0.05) urinary N excretion and urinary N per N intake and higher (p<0.1) tendency of retained N than the low RUP:RDP group. The high RUP:RDP group had higher (p<0.1) tendency of N utilization efficiency (retained N per N intake: 28.7% vs. 25.5%) than the low RUP:RDP group. The high RUP:RDP group had a lower (p<0.1) tendency of urinary N per total N excretion, but a higher tendency of fecal N per total N excretion.
Conclusion
A high ratio of dietary RUP:RDP may improve N utilization efficiency by reducing urinary N excretion, which may be beneficial for the environment through reducing atmospheric ammonia emissions.

Keywords: Dietary Rumen Undegradable Protein; Fermented Heat-treated Soybean Meal; Nitrogen Excretion; Retained Nitrogen; Korean Cattle Steers