Dias Batista Luiz F, Rivera Madeline E, Fonseca Mozart A, Tedeschi Luis O
Department of Animal Science, Texas A&M University, College Station, TX 77843-2471, USA.
Department of Agriculture, Veterinary, and Rangeland Sciences, University of Nevada, Reno, NC 89557, USA.
Transl Anim Sci. 2024 Feb 14;8:txae019. doi: 10.1093/tas/txae019. eCollection 2024.
This experiment aimed to assess the impact of virginiamycin on in vitro gas production dynamics, rumen kinetics, and nutrient digestibility in beef steers fed a grain-based diet. Nine ruminally cannulated British-crossbred steers (596 ± 49 kg) were assigned to this experiment. Animals were housed in three pens ( = 3/pen) equipped with a Calan gate feed system and water troughs. Pens were enrolled in a 3 × 3 Latin square design containing three periods of 16 d, and a 5-d washout interval between periods. Dietary treatments consisted of virginiamycin () administration at 0 (VM0), 180 (VM180), or 240 mg/d (VM240). During days 15 and 16 of each period, about 600 mL of rumen fluid and urine samples were collected before (0 h), and at 4, 8, 12, and 16 h after the morning feed (0730 hours), rumen inoculum was used to take pH and redox potential measurements immediately after collection using a portable pH and redox meter, and subsamples were taken for volatile fatty acids () and NH-N analyses, and urine samples were composited daily and analyzed for creatinine and purine derivatives () content to estimate microbial crude protein flow. During the 4-h post-morning feed rumen collection, rumen inoculum was utilized to perform in vitro gas production measurements. Fecal samples were collected on day 16 of each period to estimate nutrient digestibility using acid detergent insoluble ash as an internal marker. Animals were considered the experimental unit for the statistical analyses, and periods and squares were included as random variables. The total and rate of gas production were similar among treatments ( ≥ 0.17). The second-pool (i.e., fiber) gas production increased linearly as VM inclusion increased ( = 0.01), with VM240 being greater compared to VM180 and VM0 (7.84, 6.94, and 6.89 mL, respectively). Ruminal pH linearly increased as VM increased, with VM240 being greater than VM0 and VM180 intermediate (5.90, 5.82, and 5.86, respectively; = 0.03). The VFA concentrations did not differ ( ≥ 0.13), but the acetate-to-propionate ratio was the highest in VM240 ( = 0.005). Branched-chain VFA increased ( ≤ 0.03) while lactate concentrations decreased ( = 0.005) linearly with VM. The ruminal NH-N concentration was the lowest in the VM0 ( = 0.006). The estimated absorbed PD, purine derivative to creatinine index, and microbial N flow increased linearly with VM ( ≤ 0.07). The provision of VM influenced rumen dynamics in a dose-dependent manner.
本试验旨在评估维吉尼亚霉素对以谷物为基础日粮育肥牛体外产气动力学、瘤胃动力学及养分消化率的影响。选用9头装有瘤胃瘘管的英国杂交阉牛（体重596±49千克）进行本试验。动物被饲养在三个栏舍（每栏3头）中，栏舍配备卡兰门饲喂系统和水槽。试验采用3×3拉丁方设计，包含三个16天的周期，周期之间有5天的洗脱期。日粮处理包括分别以0（VM0）、180（VM180）或240毫克/天（VM240）的剂量添加维吉尼亚霉素。在每个周期的第15天和第16天，于晨饲（0730时）前（0小时）及晨饲后4、8、12和16小时采集约600毫升瘤胃液和尿液样本，瘤胃接种物采集后立即使用便携式pH计和氧化还原电位计测量pH值和氧化还原电位，取子样本进行挥发性脂肪酸（VFA）和NH-N分析，尿液样本每天混合并分析肌酐和嘌呤衍生物（PD）含量以估算微生物粗蛋白流量。在晨饲后4小时的瘤胃采集过程中，利用瘤胃接种物进行体外产气测量。在每个周期的第16天采集粪便样本，以酸性洗涤不溶性灰分为内标物估算养分消化率。动物被视为统计分析的试验单位，周期和区组作为随机变量。各处理间总产气量和产气速率相似（P≥0.17）。随着维吉尼亚霉素添加量的增加，第二组分（即纤维）产气量呈线性增加（P = 0.01），VM240组高于VM180组和VM0组（分别为7.84、6.94和6.89毫升）。瘤胃pH值随维吉尼亚霉素添加量增加呈线性增加，VM240组高于VM0组，VM180组介于两者之间（分别为5.90、5.82和5.86；P = 0.03）。挥发性脂肪酸浓度无差异（P≥0.13），但VM240组的乙酸与丙酸比值最高（P = 0.005）。支链挥发性脂肪酸呈线性增加（P≤0.03），而乳酸浓度随维吉尼亚霉素呈线性下降（P = 0.005）。瘤胃NH-N浓度在VM0组最低（P = 0.006）。估计的吸收PD、嘌呤衍生物与肌酐指数和微生物氮流量随维吉尼亚霉素呈线性增加（P≤0.07）。维吉尼亚霉素的添加以剂量依赖的方式影响瘤胃动力学。
