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熱應激會影響豬對日糧脂肪的利用嗎？ T. A. Kellner, L. H. Baumgard, K. J. Prusa,N. K. Gabler和J. F. Patience 熱應激降低豬只生產性能，也可能會降低胴體脂肪品質，從而給生豬產業帶來巨大損失。 本試驗旨在檢測35天育肥期內熱應激如何影響豬只對日糧脂肪（如脂肪消化率、代謝和沉積）的利用。試驗選取96頭PIC 337 × C22/C29（PIC, Inc., Hendersonville, TN）閹公豬（初重100.4± 1.2 kg）按3 × 3 析因設計隨機分到9個處理，溫度環境設置為三種，分別為：對照組（TN；穩定為24°C；自由采食）、限制采食組（PFTN；穩定為24°C；限制采食量與熱應激組相同）、熱應激組（夜間溫度一直控制為28°C 、白天溫度依次為試驗開始至第7天為33°C、第7天至第14天為33.5°C、第14天至第21天為34°C，第21天至第28天為34.5°C、第28天至第35天為35°C；自由采食）；日糧設置為三種，分別為（脂肪添加量為0%的玉米-豆粕型基礎日糧CNTR）、基礎日糧中添加有3%牛油[TAL；碘價{IV} = 41.8]、基礎日糧中添加3%玉米油[CO; 碘價IV = 123.0]。 對任何主要的指標來說，飼養環境和日糧間均無交互影響（P ≥ 0.063）。熱應激導致直腸溫度的增加（HS組是39.0°C、TN組為38.1°C 、PFTN組為38.2°C；P < 0.001）。熱應激降低了日均采食量ADFI （27.8%; P < 0.001）、平均日增重ADG （熱應激組0.72 kg/d , 對照組1.03 kg/d 、限制采食組0.78 kg/d ；P < 0.001）和肉料比G:F（熱應激組0.290、對照組組0.30、限制采食組0.319；P = 0.006）。熱應激組閹公豬相較限制采食組來說每公斤體重需多攝入1.2 Mcal 代謝能（P < 0.001）。熱應激組豬只酸水解脂肪（AEE）的全腸道表觀消化率（ATTD）相較其他組是最低的（熱應激組為59.0% 、對照組60.2%、限制采食組61.4%；P = 0.055）。玉米油組（99.3%）酸水解脂肪的全腸道真消化率（TTTD）比０％脂肪組（97.3%）和牛油組（96.3%）的要高（P = 0.012）。上市后豬頰肉的碘值隨著日糧脂肪不飽和度的增加而增加（對照組為68.5 g/100 g 、牛油組為68.2 g/100 g 、玉米油組為71.5 g/100 g ；P < 0.001）。熱應激降低了 ATGL和HSL兩個基因的mRNA豐度（P ≤ 0.041）。熱應激和玉米油使得SCD基因的mRNA豐度增加（P ≤ 0.047），且玉米油增加了FASN基因的mRNA豐度（P = 0.011）。 綜上所述，熱應激并沒有改變豬只對日糧脂肪的利用。然而，熱應激導致平均日增重、日均采食量、肉料比、熱效率的降低以及脂肪分解通路相關基因mRNA豐度的下降，從而導致熱應激組豬比限制采食組豬更肥的現象。 Does heat stress alter the pig’s response to dietary fat? T. A. Kellner, L. H. Baumgard, K. J. Prusa,N. K. Gabler and J. F. Patience Heat stress (HS) results in major losses to the pork industry via reduced growth performance and, possibly, carcass fat quality. The experimental objective was to measure the effects of HS on the pig’s response to dietary fat in terms of lipid digestion, metabolism, and deposition over a 35-d finishing period. A total of 96 PIC 337 × C22/C29 (PIC, Inc., Hendersonville, TN) barrows (initial BW of 100.4 ± 1.2 kg) were randomly allotted to 1 of 9 treatments arranged as a 3 × 3 factorial: thermoneutral (TN; constant 24°C; ad libitum access to feed), pair-fed thermoneutral (PFTN; constant 24°C; limit fed based on previous HS daily feed intake), or HS (cyclical 28°C night time, 33°C from d 0 to 7, 33.5°C from d 7 to 14, 34°C from d 14 to 21, 34.5°C from d 21 to 28, and 35°C from d 28 to 35 day time; ablibitum access to feed) and diet (a corn–soybean meal–based diet with 0% added fat [CNTR], CNTR with 3% added tallow [TAL; iodine value {IV} = 41.8], or CNTR with 3% added corn oil [CO; IV = 123.0]). No interactions between environment and diet were evident for any major response criteria (P ≥ 0.063). Rectal temperature increased due to HS (39.0°C for HS, 38.1°C for TN, and 38.2°C for PFTN; P < 0.001). Heat stress decreased ADFI (27.8%; P <0.001), ADG (0.72 kg/d for HS, 1.03 kg/d for TN, and 0.78 kg/d for PFTN; P <0.001), and G:F (0.290 for HS, 0.301 for TN, and 0.319 for PFTN; P = 0.006).Heat stress barrows required 1.2 Mcal of ME intake more per kilogram of BW gain than PFTN (P < 0.001). Heat stress tended to result in the lowest apparent total tract digestibility of acid hydrolyzed ether extract (AEE; 59.0% for HS, 60.2% for TN, and 61.4% for PFTN; P = 0.055). True total tract digestibility(TTTD) of AEE of CO-based diets (99.3%) was greater than that of CNTR (97.3%) and TAL-based diets (96.3%; P = 0.012). Environment had no impact on TTTD of AEE (P = 0.118). Environment had no impact on jowl IV at market (69.2 g/100 g for HS, 69.3 g/100 g for TN, and 69.8 g/100 g for PFTN; P = 0.624). Jowl IV at market increased with increasing degree of unsaturation of the dietary fat (68.5 g/100 g for CNTR, 68.2 g/100 g for TAL, and 71.5 g/100 g for CO; P <0.001). Heat stress decreased mRNA abundance of ATGL and HSL (P ≤ 0.041).Heat stress and CO increased mRNA abundance of SCD (P ≤ 0.047), and CO increased abundance of FASN (P = 0.011). In conclusion, HS does not alter the pig’s response to dietary fat. However, HS leads to reduced ADG, ADFI, G:F, and caloric efficiency and a suppression of mRNA abundance of genes involved in the lipolytic cascade, which resulted in a phenotype that was fatter than PFTN。 作者：李廣然 來源： 豬營養國際論壇CSIS 
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