Department of Animal Science, Texas A&M University, College Station, TX.
Cooperative Agricultural Research Center, Prairie View A&M University, Prairie View, TX.
J Anim Sci. 2019 Mar 1;97(3):1335-1346. doi: 10.1093/jas/skz007.
The use of active dried yeast (ADY) in the diets of feedlot steers may improve feed efficiency, growth performance, and reduce days on feed. Strategic timing of ADY inclusion in the diet may increase feed conversion or aid in the dietary transition from growing to finishing diets. One hundred twenty steers, blocked by weight, were fed four diets for 164 d: grower (70 d), first transition diet (7 d), second transition diet for (7 d), and finisher (80 d) in a GrowSafe System. Four treatment sequences of ADY inclusion were evaluated in a Balaam's design where steers were fed a control diet before and after the grower phase (CC), control before and ADY after the grower phase (CY), ADY before and control after the grower phase (YC), and ADY before and after the grower phase (YY). A random coefficients model was used to evaluate the following variables of interest: feeding performance and growth traits, including biometric measurements and carcass ultrasound measurements, and carcass characteristics. Treatment was a fixed effect and block was a random effect. Treatment did not affect feeding performance or behavior (P ≥ 0.14). The rate of change of biometric measurements were not different (P ≥ 0.16) across treatment groups except for rib girth circumference, which was greater for the YY and CY groups intermediate for the CC group and least for the YC group (0.828 and 0.809 vs. 0.751 vs. 0.666 cm/d, respectively; P < 0.01). Faster growth rates of rib girth circumference resulted in larger final measurements for steers that were finished on ADY (P < 0.01). Ultrasound measurements (backfat, LM area, intra-muscular fat, and rump fat) were not different across treatments (P ≥ 0.15). However, there was a tendency for the YC group to have a slower rate of back fat deposition than other treatment groups (P = 0.09). Steers' final shrunk BWs did not differ (P = 0.61), but shrink percentage was greater for CC than for YY groups (3.7% vs. 2.7%, respectively; P = 0.05). Carcass characteristics were not different across treatments (P ≥ 0.20). Crude fat, CP, ash and moisture analyses of the 9th to 11th rib section were not different across treatments, and there was no difference in adjusted final shrunk BW (P ≥ 0.45). Feeding the ADY strain used in this study to growing and finishing feedlot steers increased rib girth circumference development rate and reduced shrink loss without affecting feeding behavior, feeding performance, or carcass characteristics.
在育肥场肉牛的日粮中使用活性干酵母（ADY）可以提高饲料效率、生长性能，并减少饲养天数。在日粮中战略性地添加 ADY 的时间可能会增加饲料转化率或有助于从生长日粮向育肥日粮的过渡。120 头肉牛按体重分组，在 GrowSafe 系统中饲喂四种日粮 164 天：育肥期（70 天）、第一过渡期日粮（7 天）、第二过渡期日粮（7 天）和育肥后期日粮（80 天）。在 Balaam 设计中评估了 ADY 纳入的四种处理顺序，其中肉牛在育肥期之前和之后饲喂对照日粮（CC）、育肥期之前和之后饲喂 ADY 日粮（CY）、育肥期之前和之后饲喂对照日粮（YC）和育肥期之前和之后饲喂 ADY 日粮（YY）。使用随机系数模型评估以下感兴趣的变量：饲养性能和生长特性，包括生物测量和 carcass 超声测量以及 carcass 特性。处理是固定效应，块是随机效应。处理对饲养行为或性能没有影响（P≥0.14）。除了肋弓周长，各组的生物测量指标的变化率没有差异（P≥0.16），其中 YY 和 CY 组的变化率较大，CC 组的变化率中等，YC 组的变化率最小（0.828 和 0.809 与 0.751 与 0.666 cm/d，分别；P<0.01）。肋弓周长生长速度较快的肉牛最终测量值较大，因为它们是用 ADY 育肥的（P<0.01）。超声测量（背膘、LM 面积、肌内脂肪和臀部脂肪）在处理之间没有差异（P≥0.15）。然而，YC 组的背脂沉积速度有变慢的趋势，比其他处理组慢（P=0.09）。肉牛的最终收缩 BW 没有差异（P=0.61），但 CC 组的收缩率高于 YY 组（分别为 3.7%和 2.7%；P=0.05）。处理之间 carcass 特性没有差异（P≥0.20）。第 9 至 11 肋段的粗脂肪、CP、灰分和水分分析在处理之间没有差异，调整后的最终收缩 BW 也没有差异（P≥0.45）。在育肥场肉牛的日粮中添加本研究中使用的 ADY 菌株可增加肋弓周长的发育速度，并减少收缩损失，而不影响饲养行为、饲养性能或 carcass 特性。
