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Acta Prataculturae Sinica ›› 2017, Vol. 26 ›› Issue (11): 113-122.DOI: 10.11686/cyxb2017019

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Comparing the calculation of corn silage’s effective energy value for beef cattle using direct and regression methods

WEI Ming, CUI Zhi-Hao, CHEN Zhi-Qiang, ZHENG Yue, YAN Pei-Shi*   

  1. College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
  • Received:2017-01-18 Revised:2017-03-15 Online:2017-11-20 Published:2017-11-20

Abstract: A study was conducted to determine the digestible energy (DE), metabolizable energy (ME) and net energy (NE) values of corn silage for beef cattle by direct and regression methods. The study sought to determine the feasibility of estimating the effective energy value of a single roughage using regression techniques. Twelve bulls with similar body weight [(259±14.08) kg] were randomly divided into three groups of four. In experiment 1, bulls were fed a full corn silage diet at 3 levels of feed intake: 95%, 80% and 60% of ad libitum intake (AL). In experiment 2, bulls were fed corn silage diets with concentrate added at 3 different ratios (15%, 25% and 50% respectively). Each experiment lasted for 14 days, including a 10-d pretest period and a 4-d test period. Digestibility and respirometry tests were conducted to determine the energy metabolism of corn silage for beef cattle. The results were as follows: 1) With increasing feed intake, the nutrient digestibility, energy digestibility and metabolizability of the full corn silage diet decreased, whereas energy intake improved significantly (P<0.05). 2) The DE, ME and NE values of corn silage tended to decrease with increasing levels of feed intake, with the decreases ranging from 10.58-11.48 MJ/kg, 8.33-9.44 MJ/kg and 5.20-6.21 MJ/kg respectively. 3) Adding concentrate to corn silage significantly improved the diet’s dry matter (DM) and crude protein (CP) digestibility, whereas it did not affect the digestibility of neutral detergent fiber (NDF) and acid detergent fiber (ADF) (P>0.05). With increasing concentrate additions, the diet’s energy intake and energy digestibility increased, whereas there were no significant differences in DE metabolizability between the three groups (P>0.05). 4) According to the linear regression equations for dietary available energy value and concentrate addition, the DE, ME and NE values for corn silage were 10.53 MJ/kg, 8.29 MJ/kg and 5.35 MJ/kg, which were not different (P>0.05) from those obtained using the direct method (10.58 MJ/kg, 8.33 MJ/kg and 5.20 MJ/kg respectively) for the high level intake treatment (95% AL). In conclusion, regression and direct methods do not give different values for the effective energy value of corn silage for beef cattle, indicating that regression can be used to estimate the value of single roughage for beef cattle.