Silvestre Antonio M, Pinto Ana Carolina J, Schleifer Werner F, Miranda Lidiane S, Silva Leandro A F, Casali Daniel M, Souza Katia L R, Gasparini Vanessa G L, Cruz Gustavo D, Suen Garret, Millen Danilo D
School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18618-000, Brazil.
College of Agricultural and Technological Sciences, São Paulo State University (UNESP), Dracena 17900-000, Brazil.
Animals (Basel). 2022 Mar 24;12(7):820. doi: 10.3390/ani12070820.
The objective of this study was to examine the relationships among ruminal microbial community, rumen morphometrics, feeding behavior, feedlot performance, and carcass characteristics of Nellore cattle, classified by residual feed intake (RFI). Twenty-seven Nellore yearling bulls with an initial body weight (BW) of 423.84 ± 21.81 kg were fed in feedlot for 107 d in individual pens to determine the RFI phenotype. Bulls were categorized as high RFI (>0.5 SD above the mean, n = 8), medium RFI (±0.5 SD from the mean, n = 9), and low RFI (<0.5 SD below the mean, n = 10). At harvest, whole rumen content samples were collected from each bull to evaluate ruminal microbial community, including bacteria and protozoa. The carcass characteristics were determined by ultrasonography at the beginning and at the end of the experimental period, and behavior data were collected on d 88. As a result of ranking Nellore bulls by RFI, cattle from low-RFI group presented lesser daily dry matter intake (DMI), either in kilograms (p < 0.01) or as percentage of BW (p < 0.01) than high-RFI yearling bulls, resulting in improved gain:feed (G:F). However, variables, such as average daily gain (ADG), final BW, hot carcass weight (HCW) and other carcass characteristics did not differ (p > 0.05) across RFI groups. The eating rate of either dry matter (DM )(p = 0.04) or neutral detergent fiber (NDF) (p < 0.01) was slower in medium-RFI yearling bulls. For ruminal morphometrics an RFI effect was observed only on keratinized layer thickness, in which a thinner layer (p = 0.04) was observed in low-RFI Nellore yearling bulls. Likewise, Nellore yearling bulls classified by the RFI did not differ in terms of Shannon’s diversity (p = 0.57) and Chao richness (p = 0.98). Our results suggest that the differences in feed efficiency of Nellore bulls differing in phenotypic RFI should be attributed to metabolic variables other than ruminal microorganisms and epithelium, and deserves further investigation.
本研究的目的是考察按剩余采食量（RFI）分类的内洛尔牛的瘤胃微生物群落、瘤胃形态学、采食行为、饲养场性能和胴体特征之间的关系。27头初始体重（BW）为423.84±21.81千克的内洛尔一岁公牛在饲养场的个体栏中饲养107天，以确定RFI表型。公牛被分为高RFI（高于均值0.5个标准差以上，n = 8）、中等RFI（在均值±0.5个标准差范围内，n = 9）和低RFI（低于均值0.5个标准差以下，n = 10）。在屠宰时，从每头公牛采集整个瘤胃内容物样本，以评估瘤胃微生物群落，包括细菌和原生动物。在实验期开始和结束时通过超声检查确定胴体特征，并在第88天收集行为数据。按RFI对内洛尔公牛进行排名的结果显示，低RFI组的牛每天干物质摄入量（DMI）无论是以千克计（p < 0.01）还是以BW的百分比计（p < 0.01）都低于高RFI一岁公牛，从而提高了增重：饲料比（G:F）。然而，各RFI组之间的变量，如平均日增重（ADG）、最终BW、热胴体重（HCW）和其他胴体特征并无差异（p > 0.05）。中等RFI一岁公牛的干物质（DM）（p = 0.04）或中性洗涤纤维（NDF）（p < 0.01）采食率较慢。对于瘤胃形态学，仅在角质化层厚度上观察到RFI效应，其中低RFI内洛尔一岁公牛的角质化层较薄（p = 0.04）。同样，按RFI分类的内洛尔一岁公牛在香农多样性（p = 0.57）和 Chao 丰富度（p = 0.98）方面并无差异。我们的结果表明，表型RFI不同的内洛尔公牛在饲料效率上的差异应归因于瘤胃微生物和上皮以外的代谢变量，值得进一步研究。
