ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2014, Vol. 45 ›› Issue (11): 1815-1823.doi: 10.11843/j.issn.0366-6964.2014.11.011

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Effects of Dietary Energy Levels on Growth Performance，Digestion and Metabolism of Nutrients of Weaned Heifers

CUI Xiang1，DIAO Qi-yu1，ZHANG Nai-feng1，QIU Guo-liang2，LIU Ce1，ZENG Shu-qin1，TU Yan1*   

  1. (1.Key Laboratory of Feed Biotechnology of Ministry of Agriculture，Feed Research Institute，Chinese Academy of Agricultural Sciences，Beijing 100081，China；2.Chinese Academy of Agricultural Sciences Achievements Conversion Board，Beijing 100081，China)
  • Received:2014-03-21 Online:2014-11-23 Published:2014-11-24

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Abstract:

The current study was performed to investigate the effects of different energy levels on nutrients digestion and metabolism of weaned heifers.Thirty-two Holstein heifers aged 98 days were divided into 4 groups (A，B，C and D)，each with 8 heifers，and was fed with a diet which the net energy for lactation (NEL) was 6.24，7.04，7.53 or 7.85 MJ•kg-1 for 89 days，respectively.The weight，feed intake and glucose，urea nitrogen，and triglyceride content of serum were measured.Two digestion and metabolism trails were conducted at 151-157 and 181-187 day-old，respectively.Four heifers were randomly selected from each group，feces and urine were collected and the apparent digestibility，utilization rate of energy and nitrogen were measured.The results showed that：the average daily gain of heifers in 4 groups at aged 150-180 days were 0.77，0.91，0.86 and 1.11 kg•d-1，respectively，the value of group D was significantly higher than that of group A (P<0.05).Body weight of heifers aged 180 days had an increasing trend with the amount of dietary NEL increasing (P<0.10)；the apparent digestibility of gross energy increased before decreased (P<0.10).The NEL level had significant effect on the apparent digestibility of dry matter，neutral detergent fiber and acid detergent fiber，digestible energy and metabolic energy (P<0.05)；When heifers aged 180 days，the ratio of retained nitrogen/nitrogen intake and retained nitrogen/nitrogen digestion increased first and decreased later with dietary NEL increasing(P<0.10)，and the value of group C reached the peak.In conclusion，as for the overall nutrition balance of heifers and digestion and metabolism levels，the optimum dietary NEL of heifers is 7.53 MJ•kg-1.

Key words: heifer, apparent digestibility, energy utilization, nitrogen metabolism

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