J Anim Sci. 2017 Dec;95(12):5388-5396. doi: 10.2527/jas2017.1633.
The objective of this study was to compare pre- and postweaning growth performance, carcass characteristics, and meat quality attributes of calves that did not receive an implant or were implanted early or late in the nursing period. Crossbred steer calves ( = 135) were stratified by birth date and birth weight and randomly assigned to the following implant treatments: control (CON; no preweaning implant), 58 d (EARLY; 36 mg zeranol, administered at an average of 58 ± 13 d of age), and 121 d (LATE; 36 mg zeranol, administered at an average 121 ± 13 d of age). After weaning, steers were blocked by initial feed yard BW to 15 pens (5 pens/treatment and 9 steers/pen). All steers were implanted on d 21 after arrival at the feed yard and again on d 108 of finishing. Steer BW and ultrasound assessment of rib eye area (uREA), rib fat thickness (uRFT), and percent intramuscular fat (uIMF) were collected when implants were administered, at weaning, and on harvest day. Carcass measurements included HCW, rib eye area (REA), 12th-rib fat thickness (FT), and marbling score. Objective color (L*, a*, and b*) was recorded, and a 3.8-cm strip loin section was removed from both sides of each carcass and portioned into 2.54-cm steaks that were aged for 3 or 14 d for analysis of cook loss and Warner-Bratzler shear force (WBSF). The remaining portion of each sample was used for analysis of moisture and crude fat. Steer BW, ADG, and G:F did not differ among treatments ( > 0.05). Steers implanted in the EARLY treatment had a greater ( < 0.05) cumulative DMI than CON but were not different from steers implanted in the LATE treatment. Ultrasound REA and uRFT (averaged across all collection days) did not differ ( > 0.05); however, steers on the CON treatment had a greater ( ≤ 0.05) percent uIMF than EARLY implanted steers, whereas steers receiving the LATE implant were intermediate and not different from the other treatments. Hot carcass weight, REA, FT, USDA yield grade, marbling score, and objective color did not differ ( > 0.05) among treatments. The proportion of steers in each USDA yield and quality grade was similar ( > 0.05) among treatments, and no differences were detected for total carcass value or price per 45.4 kg (hundredweight; > 0.05). Treatment did not influence ( > 0.05) percent cook loss, crude fat, moisture, or WBSF. In conclusion, administering a nursing implant, regardless of timing, did not influence live performance, carcass characteristics, or meat quality of steers fed in this study.
本研究的目的是比较未接受植入物或在哺乳期早期或晚期接受植入物的犊牛在断奶前和断奶后的生长性能、胴体特性和肉质属性。杂交公牛犊（n=135）按出生日期和出生体重分层，随机分配到以下植入物处理组：对照组（CON；无断奶前植入物）、58 天（EARLY；在 58±13 日龄时给予 36mg 止汗隆）和 121 天（LATE；在 121±13 日龄时给予 36mg 止汗隆）。断奶后，根据初始饲料场体重将公牛分为 15 个栏（每个处理组 5 个栏，每栏 9 头公牛）。所有公牛在到达饲料场后的第 21 天和育肥结束时的第 108 天再次接受植入。当植入物给药、断奶和收获日时，收集公牛体重和超声评估的肋眼面积（uREA）、肋脂肪厚度（uRFT）和肌内脂肪百分比（uIMF）。胴体测量包括 HCW、肋眼面积（REA）、第 12 肋骨脂肪厚度（FT）和大理石花纹评分。记录客观颜色（L*、a和 b），从每具胴体的两侧取下 3.8 厘米的腰肉条，并将其分成 2.54 厘米的牛排，在 3 天或 14 天进行分析，以测定烹煮损失和 Warner-Bratzler 剪切力（WBSF）。每个样本的其余部分用于分析水分和粗脂肪。处理组之间的公牛体重、ADG 和 G:F 没有差异（>0.05）。早期处理的公牛的累积采食量（DMI）大于 CON 处理组（<0.05），但与晚期处理组的公牛没有差异。超声 REA 和 uRFT（所有采集日的平均值）没有差异（>0.05）；然而，CON 处理组的公牛的 uIMF 百分比大于 EARLY 植入组的公牛，而接受 LATE 植入的公牛则处于中间水平，与其他处理组没有差异。热胴体重、REA、FT、美国农业部产量等级、大理石花纹评分和客观颜色在处理组之间没有差异（>0.05）。每个美国农业部产量和质量等级的公牛比例在处理组之间相似（>0.05），总胴体价值或每 45.4 公斤（百磅）的价格也没有差异（>0.05）。处理组对烹煮损失、粗脂肪、水分或 WBSF 没有影响（>0.05）。总之，在本研究中，无论时间如何，给予哺乳期植入物都不会影响育肥公牛的生长性能、胴体特性或肉质。
