ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2019, Vol. 50 ›› Issue (2): 332-342.doi: 10.11843/j.issn.0366-6964.2019.02.011

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The Effect of Dietary Energy Levels on Growth Performance and Rumen Fermentation in Chinese Holstein Heifers

HUO Luman1, CAO Yufeng1, GAO Yanxia1, LI Yan2, LI Qiufeng1, LI Jianguo1,3*   

  1. 1. College of Animal Science and Technology, Hebei Agricultural University, Baoding 071001, China;
    2. College of Veterinary Medicine, Hebei Agricultural University, Baoding 071001, China;
    3. Embryo Engineering and Technological Center of Cattle and Sheep of Hebei, Baoding 071001, China
  • Received:2018-07-27 Online:2019-02-23 Published:2019-02-23

Abstract:

The objective of this study was to investigate the effect of dietary energy levels on nutrient apparent digestibility, growth performance and rumen fermentation of Chinese Holstein heifers. Forty-five Chinese Holstein heifers averaged at aged 8 months were selected and randomly allocated into 3 groups with 15 heifers in each group. Animals in group I were fed a low-energy diet (NEL 5.64 MJ·kg-1), those in group Ⅱ were fed a medium energy diet (NEL 5.94 MJ·kg-1), and those in group Ⅲ were fed a high-energy diet (NEL 6.21 MJ·kg-1). The experiment lasted for 110 d. Protein levels of the 3 diets were similar(CP14.04%). The growth performance indicators of heifer, including body weight, withers height, body length, heart girth, circumference of cannon bone, teat length and teat spacing, were determined, and fecal samples were collected for the analysis of apparent digestibility of nutrient, and the rumen fluid samples were collected for the determination of rumen pH, microbial protein(MCP), NH3-N and volatile fatty acid(VFA). The results showed that:1) Compared with group I and Ⅱ, the apparent digestibility of neutral detergent fiber (NDF) and acid detergent fiber (ADF) in group Ⅲ were significantly decreased (P<0.05). Compared with group I, the apparent digestibility of NDF in group Ⅱ and Ⅲ were decreased by 4.84% and 7.03%, and the apparent digestibility of ADF were decreased by 2.99% and 7.50%, respectively. There was no significant difference in the dry matter intake(DMI),the apparent digestibility of crude protein(CP), crude fat(EE), calcium(Ca) and phosphorus(P) among group I, Ⅱ and Ⅲ (P>0.05). 2) The average daily gain (ADG) in group I, Ⅱ and Ⅲ were 0.70, 0.80 and 0.91 kg·d-1, respectively. Compared with group I, ADG in group Ⅱ and Ⅲ were increased by 14.28% and 30.00%(P<0.05), respectively. There was no significant differences in body measurements (withers height, body length, heart girth, circumference of cannon bone) among group I, Ⅱ and Ⅲ (P>0.05). 3) Compared with group I and Ⅲ, the average length of anterior teats in group Ⅱ were increased 4.15% (P>0.05) and 9.06% (P<0.05), and the average length of posterior teats were increased 9.02%(P<0.05) and 11.54%(P<0.05), respectively. 4) There was no significant differences in rumen pH, MCP content, the concentration of acetic acid, butyric acid, total volatile fatty acids (T-VFA) and the ration of acetic acid/propionic acid (A/P) among group I, Ⅱ and Ⅲ (P>0.05). The content of ammonia nitrogen (NH3-N) was the lowest in group Ⅱ, which was significantly lower than that of group I by 3.56% (P<0.05), but there was no significant difference between group Ⅱ and Ⅲ (P>0.05). Propionic acid content in group Ⅲ was higher than that in groupⅠand Ⅱ by 4.99% (P<0.05) and 4.83%(P>0.05), respectively. In conclusion, a dietary NEL level of 5.94 MJ·kg-1 and CP level of 14% are recommended for Chinese Holstein heifers averaged at 8-11 months old.

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