Energy and protein requirements for maintenance of Southern Yellow cattle fed a corn silage or straw-based diet

The objective of this study was to estimate the net energy and net protein requirements for maintenance (NEm and NPm) of Southern Yellow cattle in China. A database involving 175 cattle with body weight (BW) ranging from 211 to 454 kg was obtained from a series of calorimetry experiments. The diets offered to cattle consisted of proportionately corn-soybean meal concentrate and roughage containing corn silage, rice straw and wheat straw. Linear regression equations of the logarithm of heat production (HP) and retained energy (RE) against metabolizable energy intake (MEI) were developed to predict the maintenance requirements for metabolizable energy (MEm) and NEm. The combined data indicated that the MEm and NEm were 522 and 348 MJ/kg0.75 of BW d−1, respectively. In addition, the partial efficiency of use of ME for maintenance was 0.66, and the partial efficiency for growth was 0.51. Similarly, there was also a linear relationship between retained nitrogen (RN) and nitrogen intake (NI). The pooled data provided a NPm of 2.63 g/kg0.75 of BW d−1 and a metabolizable protein requirement for maintenance (MPm) of 3.93 g/kg0.75 of BW d−1 for Southern Yellow cattle. In conclusion, our estimate of NEm was extremely similar to the value of the AFRC nutritional system, whereas it was slightly greater than that recommended by the NRC nutritional system. Additionally, the MPm value obtained in the current study was in agreement with the NRC recommendation.