Rigueiro André L N, Squizatti Mariana M, Silvestre Antonio M, Pinto Ana C J, Estevam Daniela D, Felizari Luana D, Dias Evandro F F, Demartini Breno L, Nunes Ana B P C, Costa Victor C M, Caixeta Eduardo L, Santi Pedro F, Soares Carlos H G, Arrigoni Mario D B, Millen Danilo D
Department of Breeding and Animal Nutrition, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, Brazil.
Department of Animal Production, College of Agricultural and Technological Sciences, São Paulo State University (UNESP), Dracena, Brazil.
Front Vet Sci. 2021 Aug 2;8:692705. doi: 10.3389/fvets.2021.692705. eCollection 2021.
Feedlot cattle are usually adapted to high-concentrate diets containing sodium monensin (MON) in more than 14 days. However, for finishing diets with lower energy content, the use of MON during adaptation may hold dry matter intake (DMI), and virginiamycin (VM) may be an alternative. This study was designed to determine the potential of shortening the adaptation of Nellore cattle to high-concentrate diets using only VM as a sole feed additive relative to feedlot performance, feeding behavior, and ruminal and cecum morphometrics. The experiment was designed as a completely randomized block replicated six times (four animals/pen) in which 120 Nellore bulls (390.4 ± 19.0 kg) were fed in 30 pens for 111 days according to the following treatments: (1) MON and adaptation for 14 days (MON14), (2) MON + VM and adaptation for 14 days (MONVM14), (3) VM and adaptation for 14 days (VM14), (4) VM and adaptation for 9 days (VM9), and (5) VM and adaptation for 6 days (VM6). At the end of the adaptation, 30 animals ( = 1 per pen) were randomly slaughtered for rumen and cecum evaluations. The remaining 90 bulls were harvested at the end of the study. No effects of treatments were observed ( < 0.10) for final body weight, average daily gain (ADG), and hot carcass weight (HCW). Cattle fed VM14 presented a greater ( ≤ 0.03) DMI, expressed as percent of body weight (BW), than animals fed either MON14 or MONVM14; however, cattle fed either MON14 or MONVM14 improved ( ≤ 0.02) the gain-to-feed ratio (G/F) by 10.4 or 8.1%, respectively, when compared to bulls fed VM14. Bulls fed VM14 had smaller ( < 0.05) papillae area (0.34 vs. 0.42 cm) and rumen absorptive surface area (28.9 vs. 33.8 cm) than those fed MON14. The shortening of the adaptation period linearly decreased the 12th rib fat ( = 0.02) and biceps femoris fat daily gain ( = 0.02) of Nellore bulls fed only VM, which linearly decreased the final biceps femoris fat thickness ( < 0.01). Feedlot cattle fed VM as a sole feed additive should not be adapted to high-concentrate diets in less than 14 days. Regardless of either adaptation length or feed additive, feedlot cattle need at least 14 days to adapt to finishing diets.
饲养场的牛通常需要14天以上的时间来适应含有莫能菌素（MON）的高浓度日粮。然而，对于能量含量较低的育肥日粮，在适应期使用莫能菌素可能会抑制干物质采食量（DMI），维吉尼亚霉素（VM）可能是一种替代选择。本研究旨在确定相对于饲养场性能、采食行为以及瘤胃和盲肠形态测量指标，仅使用维吉尼亚霉素作为唯一饲料添加剂时，缩短内洛尔牛适应高浓度日粮的可能性。实验设计为完全随机区组，重复6次（每栏4头动物），将120头内洛尔公牛（390.4±19.0千克）按照以下处理方式在30个栏中饲养111天：（1）莫能菌素并适应14天（MON14），（2）莫能菌素+维吉尼亚霉素并适应14天（MONVM14），（3）维吉尼亚霉素并适应14天（VM14），（4）维吉尼亚霉素并适应9天（VM9），以及（5）维吉尼亚霉素并适应6天（VM6）。适应期结束时，随机屠宰30头动物（每栏1头）用于瘤胃和盲肠评估。其余90头公牛在研究结束时进行屠宰。在最终体重、平均日增重（ADG）和热胴体重（HCW）方面未观察到处理效应（P<0.10）。与饲喂MON14或MONVM14的动物相比，饲喂VM14的牛以体重百分比表示的DMI更高（P≤0.03）；然而，与饲喂VM14的公牛相比，饲喂MON14或MONVM14的牛的料重比（G/F）分别提高了10.4%或8.1%（P≤0.02）。与饲喂MON14的牛相比，饲喂VM14的公牛的乳头面积（0.34对0.42平方厘米）和瘤胃吸收表面积（28.9对33.8平方厘米）更小（P<0.05）。仅饲喂维吉尼亚霉素的内洛尔公牛适应期的缩短使第12肋脂肪（P=0.02）和股二头肌脂肪日增重（P=0.02）呈线性下降，这使最终股二头肌脂肪厚度线性下降（P<0.01）。仅以维吉尼亚霉素作为唯一饲料添加剂的饲养场牛不应在少于14天的时间内适应高浓度日粮。无论适应期长短或饲料添加剂如何，饲养场的牛至少需要14天来适应育肥日粮。
