Orlowski Sara K, Dridi Sami, Greene Elizabeth S, Coy Cynthia S, Velleman Sandra G, Anthony Nicholas B
Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States.
Department of Animal Sciences, The Ohio State University, Wooster, OH, United States.
Front Physiol. 2021 Aug 25;12:712095. doi: 10.3389/fphys.2021.712095. eCollection 2021.
Muscle development during embryonic and early post-hatch growth is primarily through hyperplastic growth and accumulation of nuclei through satellite cell contribution. Post-hatch, muscle development transitions from hyperplasia to hypertrophic growth of muscle fibers. Commercial selection for breast yield traditionally occurs at ages targeting hypertrophic rather than hyperplastic growth. This has resulted in the production of giant fibers and concomitant challenges with regard to muscle myopathies. The current study investigates the impact of selection during the period of hyperplastic growth. It is hypothesized that selection for percentage breast yield during hyperplasia will result in an increased number of muscle cells at hatch and potentially impact muscle fiber characteristics at processing. This study characterizes the breast muscle histology of three broiler lines at various ages in the growth period. The lines include a random bred control (RAN) as well as lines which have been selected from RAN for high (HBY4) and low (LBY4) percentage 4-day breast yield. Post-rigor pectoralis major samples from six males of each line and age were collected and stored in formalin. The sample ages included embryonic day 18 (E18), post-hatch day 4 (d4), and day 56 (d56). The samples were processed using a Leica tissue processor, embedded in paraffin wax, sectioned, and placed on slides. Slides were stained using hematoxylin and eosin. E18 and d4 post-hatch analysis showed advanced muscle fiber formation for HBY4 and immature muscle development for LBY4 as compared to RAN. Post-hatch d56 samples were analyzed for fiber number, fiber diameter, endomysium, and perimysium spacing. Line HBY4 had the largest muscle fiber diameter (54.2 ± 0.96 μm) when compared to LBY4 (45.4 ± 0.96 μm). There was no line difference in endomysium spacing while perimysium spacing was higher for HBY4 males. Selection for percentage 4-day breast yield has impacted the rate and extent of muscle fiber formation in both the LBY4 and HBY4 lines with no negative impact on fiber spacing. The shift in processing age to later ages has exposed issues associated with muscle fiber viability. Selection during the period of muscle hyperplasia may impact growth rate; however, the potential benefits of additional satellite cells are still unclear.
胚胎期和孵化后早期生长阶段的肌肉发育主要通过增生性生长以及卫星细胞贡献使细胞核积累来实现。孵化后，肌肉发育从增生转变为肌纤维的肥大性生长。传统上，针对胸肉产量的商业选择是在以肥大性生长而非增生性生长为目标的年龄进行的。这导致了巨型纤维的产生以及与肌肉肌病相关的挑战。当前研究调查了增生性生长阶段选择的影响。研究假设，在增生期对胸肉产量百分比进行选择将导致孵化时肌肉细胞数量增加，并可能影响加工时的肌纤维特征。本研究对三个肉鸡品系在生长期间不同年龄的胸肌组织学进行了表征。这些品系包括一个随机繁殖对照品系（RAN）以及从RAN中选出的高（HBY4）、低（LBY4）4日龄胸肉产量百分比的品系。采集每个品系和年龄的六只雄性肉鸡宰后胸大肌样本，并保存在福尔马林中。样本年龄包括胚胎第18天（E18）、孵化后第4天（d4）和第56天（d56）。样本经徕卡组织处理仪处理，石蜡包埋，切片，置于载玻片上。载玻片用苏木精和伊红染色。与RAN相比，E18和孵化后d4的分析显示HBY4的肌纤维形成提前，而LBY4的肌肉发育不成熟。对孵化后d56的样本进行了纤维数量、纤维直径、肌内膜和肌束膜间距分析。与LBY4（45.4±0.96μm）相比，HBY4品系的肌纤维直径最大（54.2±0.96μm）。肌内膜间距在品系间无差异，而HBY4雄性的肌束膜间距更高。对4日龄胸肉产量百分比的选择影响了LBY4和HBY4品系中肌纤维形成的速率和程度，对纤维间距没有负面影响。加工年龄向更大年龄的转变暴露了与肌纤维活力相关的问题。在肌肉增生期进行选择可能会影响生长速度；然而，额外卫星细胞的潜在益处仍不明确。
