Effects of energy levels on growth performance, carcass characteristics, and fatty acid composition of Holstein steers at different slaughter ages

Sung Il Kim; Sungkwon Park; Hyun Soo Lee; Ji Hong Lee; Do Hyung Kim; Jeong Hwan Myung; Keun Ki Jung

doi:10.5187/jast.2023.e47

Effects of energy levels on growth performance, carcass characteristics, and fatty acid composition of Holstein steers at different slaughter ages

J Anim Sci Technol. 2023 Nov;65(6):1214-1225. doi: 10.5187/jast.2023.e47. Epub 2023 Nov 30.

Authors

Sung Il Kim¹, Sungkwon Park², Hyun Soo Lee³, Ji Hong Lee¹, Do Hyung Kim¹, Jeong Hwan Myung³, Keun Ki Jung⁴

Affiliations

¹ Department of Animal Science, Gyeongbuk Provincial College, Yecheon 36830, Korea.
² Department of Food Science and Biotechnology, Sejong University, Seoul 05006, Korea.
³ Daehan Livestock & Feed Co., Ltd, Incheon 22300, Korea.
⁴ Moksan Hanwoo Research Institute, Gyeongsan 38507, Korea.

Abstract

We investigated the effect of energy levels on growth performance, carcass characteristics, and fatty acid composition of Holstein steers at different slaughter ages. Forty Holstein steers with an average body weight (BW) of 234.21 ± 7.42 kg and 7.78 ± 0.22 months were randomly allocated to two experimental groups; a 22-month-old experimental group and a 24-month-old experimental group. Total digestible nutrients (TDN) for each group were set to 70% (T1) and 72% (T2) during fattening phase and 74% (T3) and 76% (T4) for the finishing phase, respectively. No difference was observed in the final BW between the experimental groups during the fattening phase. However, in the finishing phase, the final BW of T4 (820.31 kg) group was significantly higher than that of T1 (745.57 kg; p < 0.05). The average daily gain (ADG) of T2 group in the finishing phase and overall period were 1.27 kg and 1.26 kg, respectively, which were significantly higher than those of T1 (1.11 kg and 1.12 kg; p < 0.05). The feed conversion ratio (FCR) and TDN conversion ratio of T2 group in the finishing phase also decreased by 10.23% and 7.73%, respectively, compared to those of T1. The cold carcass weight of T4 group was significantly higher (p < 0.05) than that of T1, whereas back fat thickness, longissimus area, and marbling score were not significantly different among groups. No differences were observed in physicochemical characteristics of the carcass including moisture, crude protein, and crude fat content among groups. However, the composition of fatty acids differed significantly between the groups. The content of C18:0 was significantly lower (p < 0.05) in T4 than in T1 group, and the content of C18:2 was higher in T4 than in T1 and T3 (p < 0.05). Therefore, feeding Holstein steers at a high-energy feeding level during the fattening and finishing phases improves ADG and reduces the slaughter age from 24 months to 22 months.

Keywords: Average daily gain; Fatty acid composition; Feed conversion ratio; Holstein steer.