Stoller G M, Zerby H N, Moeller S J, Baas T J, Johnson C, Watkins L E
Ohio State University, Columbus 43210, USA.
J Anim Sci. 2003 Jun;81(6):1508-16. doi: 10.2527/2003.8161508x.
The present experiment utilized Berkshire (n = 76), Duroc (n = 81), and high-lean commercial crossbred (n = 75) barrows and gilts with an initial BW of approximately 85.1 kg. Pigs were fed a standard commercial diet (17.6% CP, 1.02% lysine) supplemented with ractopamine hydrochloride at a level of 0 or 10 ppm for 28 d. The experiment was conducted in a randomized complete block design, with animals blocked within genetic line according to litter, gender, and weight, for a total of four blocks per genetic line for each treatment. Pigs were harvested at a commercial abattoir and chilled for 24 h at 1 to 4 degrees C. At 24 h postmortem, wetness and firmness scores and ultimate muscle pH were measured in the center of the longissimus muscle (LM) at the 10th to 11th rib interface. Visual and instrumental color and marbling score were measured at 48 h postmortem on a fresh cut LM surface. Percentage of chemically extracted intramuscular fat (IMF) was measured, and a trained sensory panel evaluated cooked LM chops for juiciness, tenderness, and chewiness. Cooking loss (%) and instrumental measurement of tenderness also were measured on cooked LM chops. Ractopamine treatment increased ADG (P < 0.01) and LM area (P < 0.05), but had no effect (P > 0.05) on LM quality, sensory attributes, or instrumental measures of palatability. Berkshire LM received higher tenderness and juiciness (P < 0.05) scores and had lower cooking losses (P < 0.05) and instrumental tenderness (P < 0.05) than LM from the Duroc and high-lean lines. Loins from barrows were firmer (P < 0.05), had lower drip loss percentages (P < 0.05), and received greater tenderness scores (P < 0.05) than the LM from gilts. Genetic line x treatment and gender x treatment interactions were detected for IMF. The LM of Berkshire pigs fed ractopamine had lower (P < 0.05) IMF than Berkshires fed the control diet, with no interaction in the other lines. Purebred barrows (Berkshire and Duroc) had greater (P < 0.001 and P < 0.05, respectively) IMF than their respective purebred gilts, with no gender difference in IMF in the high-lean line. Results from the present study indicate that feeding ractopamine does not affect most muscle quality and palatability characteristics. However, the genetic line x treatment interaction for loin IMF suggests that feeding ractopamine might reduce IMF within the loin muscle of genetic lines that have a propensity to produce greater levels of IMF.
本试验选用了初始体重约85.1千克的伯克夏猪（n = 76）、杜洛克猪（n = 81）和高瘦肉率商业杂交猪（n = 75）的公猪和母猪。给猪饲喂标准商业日粮（粗蛋白含量17.6%，赖氨酸含量1.02%），添加盐酸莱克多巴胺的水平为0或10 ppm，持续28天。试验采用随机完全区组设计，根据窝别、性别和体重在遗传系内对动物进行分块，每个遗传系每种处理共分四个区组。猪在商业屠宰场屠宰，并在1至4摄氏度下冷藏24小时。宰后24小时，在第10至11肋间隙的背最长肌（LM）中部测量湿度和紧实度评分以及最终肌肉pH值。宰后48小时，在新鲜切割的LM表面测量视觉和仪器颜色以及大理石纹评分。测量化学提取的肌内脂肪（IMF）百分比，由经过训练的感官评价小组对煮熟的LM猪排的多汁性、嫩度和咀嚼性进行评价。还测量了煮熟的LM猪排的烹饪损失率（%）和嫩度的仪器测量值。莱克多巴胺处理提高了平均日增重（P < 0.01）和LM面积（P < 0.05），但对LM品质、感官特性或适口性的仪器测量值没有影响（P > 0.05）。与杜洛克猪和高瘦肉率品系的LM相比，伯克夏猪的LM嫩度和多汁性评分更高（P < 0.05），烹饪损失更低（P < 0.05），仪器测量的嫩度更低（P < 0.05）。公猪的腰肉比母猪的LM更紧实（P < 0.05），滴水损失百分比更低（P < 0.05），嫩度评分更高（P < 0.05）。检测到遗传系×处理和性别×处理对IMF有交互作用。饲喂莱克多巴胺的伯克夏猪的LM的IMF低于饲喂对照日粮的伯克夏猪，其他品系没有交互作用。纯种公猪（伯克夏猪和杜洛克猪）的IMF分别比各自的纯种母猪更高（分别为P < 0.001和P < 0.05），高瘦肉率品系的IMF没有性别差异。本研究结果表明，饲喂莱克多巴胺不影响大多数肌肉品质和适口性特征。然而，腰肉IMF的遗传系×处理交互作用表明，饲喂莱克多巴胺可能会降低倾向于产生更高水平IMF的遗传系腰肉中的IMF。
