关键词: 草原红牛, 能量, 气体代谢, 养分利用, 血清指标

Abstract:

【Objective】 This study was carried out to investigate the effects of dietary energy levels on gas metabolism, nutrient digestion and serum parameter of Steppe Red cattle. 【Method】 A total of twelve healthy Steppe Red cattle with body weight of 365.08±2.76 kg were randomly allocated into three groups. Each group was subject to one of the following 3 diets: 5.65, 6.05, and 6.43 MJ·kg^-1 of net energy for gain, defining as LE, ME and HE, respectively. Experimental period was 20 days with 18 days of adaptive phase and 2 days of testing phase, respectively. Equipment of macrofauna open-type with respiration and calorimetric function was used for respiratory calorimetry trial and digestive and metabolic trial during testing phase. Blood samples were collected from jugular vein of Steppe Red cattle to isolate serum, and serum biochemical parameters were detected. 【Result】 Data showed that methane output, methane output as a proportion of dry matter intake, oxygen consumption, and heat production in HE group were higher than those of other groups, while carbon dioxide output in HE group was higher than that of ME group (P<0.05), and all the indices above increased linearly with the increase of dietary energy (P<0.05). Analysis of energy metabolism parameters showed that digestible energy intake, metabolic energy intake, gross energy digestibility, gross energy metabolic rate, fecal energy output and urine energy output were not affected by dietary treatments (P>0.05). Methane energy output and methane energy output as a proportion of gross energy in HE group were higher than other groups (P<0.05), and the two indices increased linearly as dietary energy level increased (P<0.05). Nitrogen metabolism indices did not differ among groups (P>0.05). Apparent digestibility of dry matter, organic matter, ether extract, neutral detergent fiber and acid detergent fiber were not affected by dietary energy level (P>0.05), whereas dry matter and organic matter apparent digestibility increased linearly with the increase of dietary energy (P=0.059). HE group exhibited increased serum total triglyceride and decreased urea nitrogen (P<0.05), and both indices were linearly changed as dietary energy level increased (P<0.05). Other serum parameters were not affected (P>0.05). 【Conclusion】 Overall, increasing dietary energy level could enhance nutrient utilization, whereas energy would lose in the form of methane energy when dietary energy level was too high. In general, medium energy group achieved the best energy utilization, and the appropriate supply quantity of the digestible energy and protein for 350 kg Steppe Red cattle were 128.12 MJ·d^-1 and 749.50 g·d^-1, respectively; the metabolic energy and protein were 121.78 MJ·d^-1 were 678.75 g·d^-1, respectively; the net energy for gain was 55.96 MJ·d^-1.

Key words: Steppe Red cattle, energy, gas metabolism, nutrient utilization, serum parameter