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Asian-Australas J Anim Sci > Accepted Articles
DOI:    [Accepted] Published online January 26, 2018.
Effects of different dietary ratio of metabolizable glucose and metabolizable protein on growth performance, rumen fermentation, blood biochemical indices and ruminal microbiota of 8 to 10-month-old heifers
Jie Sun1, Jinhao Xu1, Rufang Ge1, Hongrong Wang1,*, Mengzhi Wang1, Lihuai Yu1
College of Animal Science and Technology, Yangzhou University, Yangzhou, China
Correspondence:  Hongrong Wang, Tel: +86-514-87997196, Fax: +86-514-87350440, Email:
Received: 8 December 2017   • Revised: 2 January 2018   • Accepted: 18 January 2018
Objective: The aim of this experiment was to evaluate the effects of different dietary ratios of metabolizable glucose (MG) to metabolizable protein (MP) on growth performance, blood metabolites, rumen fermentation parameters and the ruminal microbial community of 8 to 10-month-old heifers.


A total of 24 Holstein heifers weighing an average of 282.90 kg (8 month of age) were randomly assigned to four groups of six. The heifers were fed one of four diets of different dietary MG/MP (0.97, 1.07, 1.13 and 1.26).


The results showed that the ratio of MG/MP affected the growth performance, blood metabolites, rumen fermentation parameters and the ruminal microbial community of heifers. The average daily gain (ADG) of heifers was enhanced by increasing the ratio of MG/MP (P < 0.05). The concentration of blood urea nitrogen (BUN), cholesterol (CHOL) and low density lipoprotein cholesterol (LDL-C) as well as the concentration of total volatile fatty acid (VFA) in the rumen fluid of heifers decreased with the improvement in the ratio of dietary MG/MP (P < 0.05). However, the relative amount of Ruminococcus albus and Butyrivibrio fibrisolvens in the rumen of heifers was increased significantly (P < 0.05) when the dietary MG/MP increased. At the same time, with the improvement in dietary MG/MP, the amount of Fibrobacter succinogenes increased (P = 0.08).
A diet with an optimal ratio (1.13) of MG/MP was beneficial for the improvement of growth, rumen fermentation, dietary protein and energy utilization of 8 to 10-month-old heifers in this experiment.
Keywords: Metabolizable glucose; Metabolizable protein; Heifer; Rumen microbe; Fermentation parameters

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