Schoonmaker J P, Cecava M J, Fluharty F L, Zerby H N, Loerch S C
Department of Animal Sciences, The Ohio State University, Wooster 44691, USA.
J Anim Sci. 2004 Jan;82(1):273-82. doi: 10.2527/2004.821273x.
One hundred eighty-four Angus x Simmental steers (initial BW 161.7 +/- 3.4 kg) were used to determine whether different sources and amounts of energy in the growing phase could extend the growth curve and maintain high amounts of intramuscular fat deposition in early-weaned steers. Steers were allotted by source, age, and BW to one of four growing-phase (119 to 259 d of age) regimens. For three regimens, steers were weaned at 119 d of age and either 1) fed (DM basis) a 50% grain diet ad libitum (ALC); 2) limit-fed a 70% grain diet to achieve a gain of 0.8 kg/d from 119 to 192 d of age, and 1.2 kg/d from 193 to 259 d of age (LFC); or 3) fed a 60% haylage diet ad libitum from 119 to 192 d of age, and a 25% haylage diet ad libitum from 193 to 259 d of age (ALF). For the fourth regimen, steers were normal-weaned at 204 d of age and fed a silage diet from 205 to 259 d of age (NW). From 260 d of age to slaughter, all steers consumed a 70% grain (DM basis) diet. Limit-fed and ALF steers spent the most, and NW the least amount of time (P < 0.01) in the feedlot to achieve a target fat depth of 1.27 cm. Ad libitum-fed steers were the youngest (331 d), and NW the oldest (383 d) at slaughter (P < 0.01). Overall ADG was greatest for ALC and least for NW steers (P < 0.01). Overall, ALF steers consumed the most DM (P < 0.01). While in the feedlot, LFC and ALC steers were more efficient in converting feed to BW gain (P < 0.01) than ALF and NW steers. Normal-weaned had the least and ALC the greatest (P < 0.01) fat depth at 260 d of age. Consequently, NW steers produced the heaviest, and ALC the lightest (P < 0.01) carcasses at slaughter. Normal-weaned steers had the largest, and ALC and LFC steers had the smallest longissimus muscle area (P < 0.06). Growing phase dietary treatments did not affect (P > 0.20) yield grade. Marbling score did not differ (P > 0.35), but laboratory analysis revealed that ALC steers had the lowest percentage of fat (P < 0.02) in the longissimus muscle. Shear force was greatest (P < 0.08) for steaks from ALC and LFC steers, and least for steaks from ALF and NW steers. Feeding steers the ALC diet from 119 to 260 d of age hastened physiological maturity, decreased marbling scores, and decreased muscle tenderness compared with forage feeding (ALF, NW). Limit-feeding a high-grain diet also hastened physiological maturity and decreased muscle tenderness but did not decrease marbling scores. Source and amount of energy affected partitioning of fat deposition.
选用184头安格斯×西门塔尔杂交阉牛（初始体重161.7±3.4千克），以确定生长阶段不同能量来源和水平是否能延长生长曲线，并使早期断奶阉牛维持较高的肌内脂肪沉积量。阉牛按来源、年龄和体重分配到四个生长阶段（119至259日龄）的饲养方案中。在三个饲养方案中，阉牛在119日龄断奶，然后：1）自由采食（以干物质计）50%谷物日粮（ALC）；2）限量饲喂70%谷物日粮，使119至192日龄日增重达到0.8千克，193至259日龄日增重达到1.2千克（LFC）；或3）119至192日龄自由采食60%青贮干草日粮，193至259日龄自由采食25%青贮干草日粮（ALF）。在第四个饲养方案中，阉牛在204日龄正常断奶，205至259日龄饲喂青贮日粮（NW）。从260日龄至屠宰，所有阉牛均采食70%谷物（以干物质计）日粮。达到1.27厘米目标脂肪厚度时，限量饲喂和ALF组阉牛在育肥期停留时间最长，NW组最短（P<0.01）。自由采食组阉牛屠宰时最年轻（331日龄），NW组最老（383日龄）（P<0.01）。总体平均日增重ALC组最高，NW组最低（P<0.01）。总体而言，ALF组阉牛干物质采食量最大（P<0.01）。在育肥期，LFC组和ALC组阉牛饲料转化为体重增加的效率高于ALF组和NW组（P<0.01）。260日龄时，正常断奶组阉牛脂肪厚度最薄，ALC组最厚（P<0.01）。因此，NW组阉牛屠宰时胴体最重，ALC组最轻（P<0.01）。正常断奶组阉牛背最长肌面积最大，ALC组和LFC组最小（P<≤0.06）。生长阶段日粮处理对产量等级无影响（P>0.20）。大理石花纹评分无差异（P>0.35），但实验室分析表明，ALC组阉牛背最长肌脂肪百分比最低（P<0.02）。ALC组和LFC组阉牛牛排的剪切力最大（P<0.08），ALF组和NW组阉牛牛排的剪切力最小。与饲喂牧草（ALF、NW）相比，119至260日龄给阉牛饲喂ALC日粮可加速生理成熟，降低大理石花纹评分，并降低肌肉嫩度。限量饲喂高谷物日粮也可加速生理成熟并降低肌肉嫩度，但不会降低大理石花纹评分。能量来源和水平影响脂肪沉积的分配。
