2016. J. Anim. Sci. 94(11): 4688-4703
热应激会影响猪对日粮脂肪的利用吗？
T. A. Kellner, L. H. Baumgard, K. J. Prusa,N. K. Gabler和J. F. Patience
热应激降低猪只生产性能，也可能会降低胴体脂肪品质，从而给生猪产业带来巨大损失。
本试验旨在检测35天育肥期内热应激如何影响猪只对日粮脂肪（如脂肪消化率、代谢和沉积）的利用。试验选取96头PIC 337 × C22/C29（PIC, Inc., Hendersonville, TN）阉公猪（初重100.4± 1.2 kg）按3 × 3 析因设计随机分到9个处理，温度环境设置为三种，分别为：对照组（TN；稳定为24°C；自由采食）、限制采食组（PFTN；稳定为24°C；限制采食量与热应激组相同）、热应激组（夜间温度一直控制为28°C 、白天温度依次为试验开始至第7天为33°C、第7天至第14天为33.5°C、第14天至第21天为34°C，第21天至第28天为34.5°C、第28天至第35天为35°C；自由采食）；日粮设置为三种，分别为（脂肪添加量为0%的玉米-豆粕型基础日粮CNTR）、基础日粮中添加有3%牛油[TAL；碘价{IV} = 41.8]、基础日粮中添加3%玉米油[CO; 碘价IV = 123.0]。
对任何主要的指标来说，饲养环境和日粮间均无交互影响（P ≥ 0.063）。热应激导致直肠温度的增加（HS组是39.0°C、TN组为38.1°C 、PFTN组为38.2°C；P <>）。热应激降低了日均采食量ADFI （27.8%; P <>）、平均日增重ADG （热应激组0.72 kg/d , 对照组1.03 kg/d 、限制采食组0.78 kg/d ；P <>）和肉料比G:F（热应激组0.290、对照组组0.30、限制采食组0.319；P = 0.006）。热应激组阉公猪相较限制采食组来说每公斤体重需多摄入1.2 Mcal 代谢能（P <>）。热应激组猪只酸水解脂肪（AEE）的全肠道表观消化率（ATTD）相较其他组是最低的（热应激组为59.0% 、对照组60.2%、限制采食组61.4%；P = 0.055）。玉米油组（99.3%）酸水解脂肪的全肠道真消化率（TTTD）比０％脂肪组（97.3%）和牛油组（96.3%）的要高（P = 0.012）。上市后猪颊肉的碘值随着日粮脂肪不饱和度的增加而增加（对照组为68.5 g/100 g 、牛油组为68.2 g/100 g 、玉米油组为71.5 g/100 g ；P <>）。热应激降低了 ATGL和HSL两个基因的mRNA丰度（P ≤ 0.041）。热应激和玉米油使得SCD基因的mRNA丰度增加（P ≤ 0.047），且玉米油增加了FASN基因的mRNA丰度（P = 0.011）。
综上所述，热应激并没有改变猪只对日粮脂肪的利用。然而，热应激导致平均日增重、日均采食量、肉料比、热效率的降低以及脂肪分解通路相关基因mRNA丰度的下降，从而导致热应激组猪比限制采食组猪更肥的现象。
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.
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