Rauw Wendy M, Mayorga E Johana, Lei Soi Meng, Dekkers Jack C M, Patience John F, Gabler Nicholas K, Lonergan Steven M, Baumgard Lance H
Departamento de Mejora Genética Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain.
Department of Animal Science, Iowa State University, Ames, IA, United States.
Front Genet. 2017 Oct 26;8:155. doi: 10.3389/fgene.2017.00155. eCollection 2017.
Heat stress (HS) is one of the costliest issues in the U.S. pork industry. Aims of the present study were to determine the consequences of repeated exposure to HS on growth performance, and the effects of a high fiber diet, the genetic potential for high lean tissue accretion, and the genetic potential for residual feed intake (RFI) on resilience to HS. Barrows ( = 97) from three genetic lines (commercial, high RFI, low RFI) where subjected three times to a 4-day HS treatment (HS1, HS2, and HS3) which was preceded by a 9-day neutral (TN) adaptation period (TN1) and alternated by 7-day periods of neutral temperatures (TN2, TN3, and TN4). Body weight gain (BWG), feed intake (FI), feed conversion efficiency (FCE), RFI, and the drop in BWG and FI between TN and HS were estimated for each period, and slaughter traits were measured at the end of TN4. Commercial pigs had lower FI when fed a high fiber diet compared to a regular diet (2.70 ± 0.08 vs. 2.96 ± 0.08 kg/d; < 0.05), while no differences were found for BWG, RFI or FCE. HS reduced FI, BWG, and FCE, increased RFI, and resulted in leaner pigs that generate smaller carcasses at slaughter. In TN, commercial pigs grew faster than the low and high RFI pigs (1.22 ± 0.06 vs. 0.720 ± 0.05 and 0.657 ± 0.07; < 0.001) but growth rates were not significantly different between the lines during HS. Growth rates for the low RFI and high RFI pigs were similar both during TN and during HS. Pigs of interest for genetic improvement are those that are able to maintain growth rates during HS. Our results show that response in growth to HS was repeatable over subsequent 4-d HS cycles, which suggests the potential for including this response in the breeding index. The best performing animals during HS are likely those that are not highly superior for growth in TN.
热应激（HS）是美国猪肉行业成本最高的问题之一。本研究的目的是确定反复暴露于热应激对生长性能的影响，以及高纤维日粮、高瘦肉组织生长的遗传潜力和剩余采食量（RFI）的遗传潜力对热应激恢复力的影响。来自三个遗传品系（商业品系、高RFI品系、低RFI品系）的97头公猪接受了三次为期4天的热应激处理（HS1、HS2和HS3），在此之前有一个为期9天的中性（TN）适应期（TN1），并交替进行为期7天的中性温度期（TN2、TN3和TN4）。估计每个时期的体重增加（BWG）、采食量（FI）、饲料转化率（FCE）、RFI，以及TN和HS之间BWG和FI的下降情况，并在TN4结束时测量屠宰性状。与常规日粮相比，商业猪饲喂高纤维日粮时FI较低（2.70±0.08对2.96±0.08千克/天；P<0.05），而BWG、RFI或FCE未发现差异。热应激降低了FI、BWG和FCE，增加了RFI，并导致猪在屠宰时更瘦、胴体更小。在TN期，商业猪比低RFI和高RFI猪生长更快（1.22±0.06对0.720±0.05和0.657±0.07；P<0.001），但在热应激期间各品系之间的生长速度没有显著差异。低RFI和高RFI猪在TN期和热应激期间的生长速度相似。对遗传改良有意义的猪是那些在热应激期间能够保持生长速度的猪。我们的结果表明，在随后的4天热应激周期中，对热应激的生长反应是可重复的，这表明有可能将这种反应纳入育种指数。热应激期间表现最佳的动物可能是那些在TN期生长优势不高的动物。
