Abstract:

【Objective】 The study was conducted to evaluate the dietary protein to metabolizable energy ratios on growth performance and nutrients digestion of the 8-10-month-old Chinese Holstein heifers. 【Method】 Eighteen 7-month-old Chinese Holstein heifers (234±21.9 kg of BW) were divided into 3 groups in a randomized experiment design with the treatment period of 90 d. Each group was randomly assigned to one of three treatment rations with a CP:ME ratios of 46.2(Group A),54.2 (Group B) or 62.0 (Group C) g of CP per Mcal ME. The ratio of dietary protein to energy was altered by adjusting the concentration of CP with a similar amount of energy across all diets. Three periods metabolism trials were carried out on 21-28 days, 51-58 days and 81-88 days after formal tests, by AIA method. 【Result】 The results showed that ADG did not differ among the treatments (P＞0.05) and the growth curves of all groups in 8-10 months were similar. The apparent digestibility of CP increased with the increasing CP:ME ratios(P＜0.05). The apparent digestibility of the nutrients increased with the age and became steady after nine months of the feeding trials. The increased CP:ME ratios were accompanied by increasing concentration of plasma urea N. 【Conclusion】 The diet of CP:ME ratios was 46.2 g of CP per Mcal ME, could meet the needs of the 8-10-month-old Chinese Holstein calves gaining 0.80-1.0 kg•d-1.

Key words: Holstein')">Holstein, protein energy ratio, heifer, growth performance, apparent digestibility