North Florida Research and Education Center, University of Florida, Marianna, FL 32446, USA.
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton AB T6G 2P5, Canada.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skac312.
Eighty-four Angus crossbred heifers (13 ± 1 mo of age, 329.5 ± 61.92 kg of body weight [BW]) were used in a generalized randomized block design with a 2 × 2 factorial arrangement of treatments. The factors evaluated were: 1) diet type (whole plant sorghum silage [SS] vs. byproducts-based [BP]), and 2) feed additive: Aspergillus oryzae prebiotic (AOP; 2 g/d) vs. Negative control (CTL; 0 g/d), resulting in four treatments: sorghum silage-control (SC), sorghum silage-AOP (SA), byproducts-control (BC), and byproducts-AOP (BA). Heifers were stratified by body weight (BW), randomly assigned to treatments (21 heifers per treatment) and housed in 12 pens equipped with two GrowSafe feed bunks each to measure individual dry matter intake (DMI). After a 14-d adaptation, BW was measured every 14 d for 56 d. Chewing activity was monitored through collar-mounted HR-Tags (heat-related tags). Following the performance period, apparent total tract digestibility was measured in 40 heifers, using indigestible neutral detergent fiber as a marker. Heifers fed with the BP diets had greater DMI (2.92% vs. 2.59% of BW, P < 0.01) and average daily gain (ADG; 1.16 vs. 0.68 kg, P ≤ 0.01) than heifers fed with SS diets. Compared with BP-fed animals, heifers consuming the SS diets had 23 more visits/d to the feed bunks (P ≤ 0.01), consumed 53% less dry matter on each visit (P ≤ 0.01), and spent 39% more min chewing/d and 63% more min chewing/kg of DMI (P ≤ 0.01). However, chewing measured in min/kg of neutral detergent fiber intake was not affected by treatment (average 111.3 min/kg of NDF intake). Feeding AOP improved gain:feed (GF) by 15% in BP-fed heifers (0.120 vs. 0.104 kg/kg; P < 0.05). Inclusion of AOP increased organic matter digestibility (OMD) in SS diets (55.88% vs. 49.83%; P < 0.01), whereas it decreased OMD in BP diets (61.67% vs. 65.77%; P < 0.05). In conclusion, ADG and GF of BP-fed heifers was greater than SS-fed heifers, and GF was greater with AOP supplementation in BP-fed heifers. Improvement in GF in BP-fed heifers was likely not related to differences in nutrient digestibility as AOP inclusion did not enhance digestibility in the BP diet. Additionally, the effects of the AOP inclusion appear to be diet-dependent, where the 15% improvement in GF by AOP occurred in heifers fed with the more fermentable diet. Therefore, further research should explore the mechanisms responsible for the observed improvements in growth performance when feeding AOP to BP-fed heifers.
84 头安格斯杂交小母牛（13±1 月龄，329.5±61.92kg 体重）采用广义随机区组设计，具有 2×2 因子处理的析因安排。评估的因素是：1）日粮类型（全株高粱青贮[SS]与副产品基[BP]），2）饲料添加剂：米曲霉益生元（AOP；2g/d）与阴性对照（CTL；0g/d），结果得到 4 种处理：高粱青贮对照（SC）、高粱青贮 AOP（SA）、副产品对照（BC）和副产品 AOP（BA）。小母牛按体重（BW）分层，随机分配到处理组（每组 21 头），并安置在 12 个配备两个 GrowSafe 饲料仓的围栏中，以测量个体干物质采食量（DMI）。适应期为 14d 后，56d 内每 14d 测量一次 BW。通过佩戴在项圈上的 HR-Tag（与热相关的标签）监测咀嚼活动。在性能期结束后，在 40 头小母牛中使用不消化中性洗涤纤维作为标记测量表观全肠道消化率。与 SS 日粮相比，饲喂 BP 日粮的小母牛 DMI（BW 的 2.92%比 2.59%，P＜0.01）和平均日增重（ADG；1.16 比 0.68kg，P≤0.01）更高。与 SS 日粮相比，饲喂 BP 日粮的小母牛每天去饲料仓的次数多 23 次（P≤0.01），每次访问的干物质摄入量少 53%（P≤0.01），每分钟咀嚼次数多 39%（P≤0.01），每千克 DMI 的咀嚼时间多 63%（P≤0.01）。然而，处理对中性洗涤纤维摄入量的咀嚼测量没有影响（平均每分钟 111.3 分钟/kg 的 NDF 摄入量）。在 BP 日粮中添加 AOP 可提高增重：饲料（GF）15%（0.120 比 0.104kg/kg；P＜0.05）。AOP 的添加提高了 SS 日粮的有机物消化率（OMD）（55.88%比 49.83%；P＜0.01），而在 BP 日粮中降低了 OMD（61.67%比 65.77%；P＜0.05）。总之，BP 日粮的 ADG 和 GF 高于 SS 日粮，BP 日粮中添加 AOP 提高了 GF。BP 日粮中 GF 的提高可能与养分消化率的差异无关，因为 AOP 的添加并未提高 BP 日粮的消化率。此外，AOP 的添加效果似乎取决于日粮，AOP 使 GF 提高了 15%，发生在饲喂更可发酵日粮的小母牛中。因此，应进一步研究当向 BP 日粮的小母牛添加 AOP 时，观察到的生长性能提高的机制。
Trop Anim Health Prod. 2023-2-20
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