Blood metabolites and fecal starch as indicators of feed efficiency of beef cattle in the feedlot

ABSTRACT The use of blood metabolites (BM), fecal starch (FS), and apparent digestion of starch, (ATTSD) as indicators of feed efficiency (FE) in beef cattle in the feedlot was studied. Fourteen bulls were used, originating in an industrial cross, without a defined racial group, with mean body weight of 284.86kg, individually fed, being evaluated in a 42-day confinement system. After the evaluation, the animals were divided into two groups according to the individual FE: high feed efficiency (HE) and low feed efficiency (LE). There was a difference between the groups in the variables FE, feed conversion (FC), final weight (FW), and daily weight gain (DWG). The FE had a positive correlation with DWG, FC, and FW. There was no difference between the groups for the variables BM, FS, and ATTSD, nor was there any correlation between these variables and FE. Considering the feed cost, the HE animals proved more profitable. BM, FS, and ATTSD did not statistically show potential to be used as indicators of FE, despite the evidence of numerical differences of these variables between the different groups, tendency of correlations with FE, and discriminating function with potential assertiveness.

摘要
本研究探讨了血液代谢物（blood metabolites, BM）、粪便淀粉（fecal starch, FS）及淀粉表观消化率（apparent digestion of starch, ATTSD）作为育肥场肉牛饲料效率（feed efficiency, FE）指标的可行性。试验选用14头源自工业杂交、无明确品种群的肉牛，初始平均体重为284.86kg，采用单栏个体饲喂方式，在42天圈养育肥体系中开展试验。试验结束后，根据个体饲料效率将试验牛分为高饲料效率（HE）组与低饲料效率（LE）组。两组在饲料效率、饲料转化率（feed conversion, FC）、末重（final weight, FW）及日增重（daily weight gain, DWG）等指标上存在显著差异。饲料效率与日增重、饲料转化率及末重呈正相关。血液代谢物、粪便淀粉及淀粉表观消化率在两组间无显著差异，且上述指标与饲料效率均未表现出相关性。从饲养成本角度考量，高饲料效率组肉牛展现出更高的养殖收益。尽管不同组别间上述三项指标存在数值差异，且与饲料效率呈现一定的相关趋势，同时存在具备潜在判别效力的判别函数，但血液代谢物、粪便淀粉及淀粉表观消化率并未在统计学层面显示出可作为饲料效率指标的应用潜力。