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Anim Biosci > Accepted Articles
https://doi.org/10.5713/ab.22.0387    [Accepted] Published online January 11, 2023.
Prediction of TDN and CP requirements according to daily weight gain, and behavioral measurements of Hanwoo heifers
Ju Ri Kim1  , Jun Sik Woo1  , Youl Chang Baek2  , Sun Sik Jang2  , Keun Kyu Park1,* 
1Department of Animal Science and Technology, Konkuk University, Seoul 05029, Korea
2National Institute of Animal Science, Rural Development Administration, Jeonbuk 55365, Korea
Correspondence:  Keun Kyu Park, Tel: +82-2-450-3661, Fax: +82-2-455-1044, Email: kkpark@konkuk.ac.kr
Received: 10 October 2022   • Revised: 14 November 2022   • Accepted: 10 January 2023
This study was conducted to investigate the effects of energy and protein levels in the diet of Hanwoo heifers on growth response and animal behavior.
Forty heifers were randomly allocated into three ex¬perimental groups according to the target daily weight gain in 8 pens (T- 0.2, 2 replications; T-0.4 and -0.6, 3 replications) based on similar body weight and age in months. The target ADG was set at 0.2 (T-0.2), 0.4 (T-0.4), and 0.6 kg/d (T-0.6), and feed was based on National Institute of Animal Science (NIAS, 2017). In order to minimize hunger stress of T-0.2 and -0.4, the feeding ratio of rice straw was set to 55, 50 and 45% for T-0.2, -0.4 and T-0.6, respectively, so that the DM intake for all treatment groups was uniform but the energy and protein levels in the diet were adjusted differently. A total of 6 items (lying, standing, eating, rumination, walking and drinking) of animal behavior were analyzed.
During the whole period of the experiment, the ADG of the T-0.2, -0.4 and -0.6 treatments were 0.48, 0.56 and 0.65 kg/d (P<0.05), respectively, showing higher gain than the predicted value, especially for the low target ADG group. Based on these results, regression equations for the TDN and CP requirements were derived. No behavioral differences were found according to the energy and protein levels in the diet because the DM intake was kept constant by adjusting the roughage and concentration ratio. However, eating time was longer (P<0.05) at T-0.2 than T-0.6 during the whole day.
Through this study, it was possible to derive regression equations for predicting TDN and CP requirements according to the target ADG and BW.
Keywords: Animal Behaviors; Hanwoo; Heifers; Nutrients; Requirements

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