莫能菌素撤药对采食百慕大干草的阉公牛和公牛的采食量、消化率及瘤胃发酵参数的影响。

Effect of monensin withdrawal on intake, digestion, and ruminal fermentation parameters by and steers consuming bermudagrass hay.

作者信息

Bell N L, Callaway T R, Anderson R C, Franco M O, Sawyer J E, Wickersham T A

出版信息

J Anim Sci. 2017 Jun;95(6):2747-2757. doi: 10.2527/jas.2016.1013.

DOI:10.2527/jas.2016.1013

Abstract

Effects of monensin withdrawal and cattle subspecies on the utilization of bermudagrass hay (14.3% CP, 72.3% NDF, and 36.9% ADF) were evaluated using ruminally cannulated steers (5 [BI] and 5 [BT]). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments consisted of either 0 mg·steer·d-1 monensin with no previous monensin feeding (CON) or withdrawal from 200 mg·steer·d-1 monensin (MON) fed individually in 0.91 kg dried distillers' grains with solubles for 42 d. Withdrawal was evaluated for a 28-d period. Ruminal fluid was collected 2 h after feeding on d 0, 1, 4, 7, 14, and 21 after withdrawal for determination of pH, VFA, ruminal NH-N (RAN), rate of NH production, and CH production rate. Hay, ort, and fecal grab samples were collected d 23 through 28 after withdrawal for determination of intake and digestion. No subspecies × monensin, subspecies × day, or subspecies × monensin × day interactions were observed ( ≥ 0.11). An effect of day after monensin withdrawal was observed ( < 0.01) for total VFA concentration, with an increase following withdrawal followed by a decrease and then stabilization. Monensin × day after monensin withdrawal interactions ( ≤ 0.01) were observed for the acetate:propionate (A:P) ratio and molar percent of acetate and propionate. There was a decrease in molar percent of propionate between d 1 and 4 from 19.1 to 18.0; however, it remained greater ( ≤ 0.10) for MON than CON through d 7. Withdrawal increased molar percent of acetate from 68.3 to 69.8 between d 0 and 4 for MON steers. The A:P ratio was less ( ≤ 0.01) on d 0 for MON than for CON (3.4 vs. 4.0), but by d 4, it increased to 3.8 and was not different ( = 0.14) from CON. By d 14, no differences ( ≥ 0.88) remained for acetate, propionate, or the A:P ratio. After monensin withdrawal, monensin reduced ( < 0.01) RAN by 12.3% (2.09 vs. 1.83 m for CON and MON, respectively). Monensin withdrawal and cattle subspecies had no effect ( ≥ 0.23) on rate of NH production or CH production rate. Monensin withdrawal had no effect ( ≥ 0.45) on intake or digestibility parameters. Greater forage OM intake ( = 0.09; 21.2 vs. 19.2 g/kg BW) and OM digestibility ( < 0.01; 72.4 vs. 63.0%) resulted in greater ( < 0.01) total digestible OM intake (16.8 vs. 13.2 g/kg BW) in BT steers than in BI steers. These results suggest that BT steers are better able to utilize bermudagrass hay than BI steers. Upon monensin withdrawal, steers previously fed monensin continue to have a reduced A:P ratio for at least 7 d.

摘要

使用瘤胃插管的阉牛（5头婆罗门牛[BI]和5头婆罗门×瘤牛杂交牛[BT]）评估莫能菌素撤饲和牛的亚种对百慕大干草（粗蛋白含量14.3%、中性洗涤纤维含量72.3%、酸性洗涤纤维含量36.9%）利用的影响。亚种同时采用两期、两处理交叉设计。处理包括：从未饲喂过莫能菌素的0 mg·头·d⁻¹莫能菌素（对照组），或从单独在0.91 kg干酒糟及其可溶物中添加200 mg·头·d⁻¹莫能菌素饲喂42 d后进行撤饲（莫能菌素组）。撤饲评估期为28 d。在撤饲后第0、1、4、7、14和21天饲喂后2 h采集瘤胃液，测定pH值、挥发性脂肪酸（VFA）、瘤胃氨态氮（RAN）、氨产生速率和甲烷产生速率。在撤饲后第23至28天采集干草、剩料和粪便抓取样本，测定采食量和消化率。未观察到亚种×莫能菌素、亚种×天数或亚种×莫能菌素×天数的交互作用（P≥0.11）。观察到撤饲后天数对总VFA浓度有影响（P<0.01），撤饲后总VFA浓度先升高，随后下降，然后趋于稳定。观察到莫能菌素撤饲后天数与莫能菌素的交互作用（P≤0.01）对乙酸:丙酸（A:P）比值以及乙酸和丙酸的摩尔百分比有影响。在第1至4天，丙酸的摩尔百分比从19.1%降至18.0%；然而，在第7天之前，莫能菌素组的丙酸摩尔百分比仍高于对照组（P≤0.10）。对于莫能菌素组的阉牛，撤饲使乙酸的摩尔百分比在第0至4天从68.3%增加到69.8%。在第0天，莫能菌素组的A:P比值低于对照组（P≤0.01）（3.4对4.0），但到第4天，该比值增加到3.8，与对照组无差异（P = 0.14）。到第14天，乙酸、丙酸或A:P比值均无差异（P≥0.88）。撤饲后，莫能菌素使RAN降低（P<0.01）12.3%（对照组和莫能菌素组分别为2.09和1.83 mmol/L）。莫能菌素撤饲和牛的亚种对氨产生速率或甲烷产生速率无影响（P≥0.23）。莫能菌素撤饲对采食量或消化率参数无影响（P≥0.45）。与BI阉牛相比，BT阉牛的牧草有机物质采食量更高（P = 0.09；21.2对19.2 g/kg体重）且有机物质消化率更高（P<0.01；72.4%对63.0%），从而使总可消化有机物质采食量更高（P<0.01；16.8对13.2 g/kg体重）。这些结果表明，BT阉牛比BI阉牛更能有效地利用百慕大干草。撤饲莫能菌素后，之前饲喂莫能菌素的阉牛的A:P比值至少在7 d内持续降低。