Lancaster P A, Sharman E D, Horn G W, Krehbiel C R, Starkey J D
Oklahoma Agricultural Experiment Station, Stillwater 74078.
J Anim Sci. 2014 Apr;92(4):1462-72. doi: 10.2527/jas.2013-6976. Epub 2014 Feb 10.
The objective of this study was to determine the impact of stocker production systems differing in growth rate on differential adipogenic and lipogenic gene expression of intramuscular (IM), subcutaneous (SC), and perirenal (PR) adipose tissues. Angus steers were assigned to 4 stocker cattle production systems in 2 consecutive years: 1) cottonseed meal-based supplement while grazing dormant native range (CON), 2) ground corn/soybean meal-based supplement while grazing dormant native range (CORN), 3) grazing wheat pasture at a high stocking rate for a low rate of BW gain (LGWP), and 4) grazing wheat pasture at a low stocking rate for a high rate of BW gain (HGWP). Steers were harvested during the stocker phase at similar age (different carcass weight) in Exp. 1 (3 steers/treatment) or at similar carcass weight in Exp. 2 (4 steers/treatment). Adipose tissues were analyzed for mRNA expression of adipogenic (peroxisome proliferator activated receptor γ [PPARγ], sterol regulatory element binding factor 1 [SREBF1], CAATT/enhancer binding protein β, and delta-like homolog 1) and lipogenic (glycerol-3-phosphate dehydrogenase [GPDH], fatty acid synthase [FASN], and diacylglycerol acyltransferase 2 [DGAT2]) genes. Multivariate analysis was used to evaluate the expression of adipogenic or lipogenic genes collectively. There was not a treatment × adipose tissue interaction (F-test, P > 0.15) when steers were harvested at similar age, but a treatment × adipose tissue interaction (F-test, P < 0.05) was evident when steers were harvested at similar carcass weight. At similar carcass weight, treatment had no effect (P > 0.10) on the canonical variate of adipogenic or lipogenic mRNA expression in IM adipose tissue, but faster rates of gain of LGWP and HGWP steers increased (P < 0.10) the canonical variate of adipogenic and lipogenic mRNA expression in SC and PR adipose tissue compared with CON and CORN steers. Strong positive correlations (P < 0.05) of PPARγ, SREBF1, GPDH, FASN, and DGAT2 mRNA expression with the canonical variate indicate that these genes strongly influenced differences between treatments and adipose tissues. These results suggest that contrary to our hypothesis rate of gain has little influence on differentiation and lipid synthesis of IM adipose tissue at similar carcass weight but faster rates of gain increase differentiation and lipid synthesis of SC and PR adipose tissue even at similar carcass weight.
本研究的目的是确定生长速度不同的架子牛生产系统对肌肉内（IM）、皮下（SC）和肾周（PR）脂肪组织中脂肪生成和脂肪形成相关基因差异表达的影响。连续两年将安格斯阉牛分配到4种架子牛生产系统中：1）在休牧的天然牧场放牧时以棉籽粕为基础的补充饲料（CON），2）在休牧的天然牧场放牧时以玉米粉/豆粕为基础的补充饲料（CORN），3）以高饲养密度放牧小麦牧场，体重增加速度低（LGWP），4）以低饲养密度放牧小麦牧场，体重增加速度高（HGWP）。在试验1中，架子牛在架子牛阶段以相似年龄（胴体重量不同）屠宰（每个处理3头阉牛）；在试验2中，以相似胴体重量屠宰（每个处理4头阉牛）。分析脂肪组织中脂肪生成相关基因（过氧化物酶体增殖物激活受体γ[PPARγ]、固醇调节元件结合因子1[SREBF1]、CAATT/增强子结合蛋白β和δ样同源物1）和脂肪形成相关基因（甘油-3-磷酸脱氢酶[GPDH]、脂肪酸合酶[FASN]和二酰甘油酰基转移酶2[DGAT2]）的mRNA表达。采用多变量分析来综合评估脂肪生成或脂肪形成相关基因的表达。当架子牛以相似年龄屠宰时，不存在处理×脂肪组织的交互作用（F检验，P>0.15），但当架子牛以相似胴体重量屠宰时，处理×脂肪组织的交互作用明显（F检验，P<0.05）。在相似胴体重量下，处理对IM脂肪组织中脂肪生成或脂肪形成mRNA表达的典型变量没有影响（P>0.10），但与CON和CORN阉牛相比，LGWP和HGWP阉牛较快的增重速度增加了（P<0.10）SC和PR脂肪组织中脂肪生成和脂肪形成mRNA表达的典型变量。PPARγ、SREBF1、GPDH、FASN和DGAT2 mRNA表达与典型变量之间存在强正相关（P<0.05），表明这些基因强烈影响处理和脂肪组织之间的差异。这些结果表明，与我们的假设相反，在相似胴体重量下，增重速度对IM脂肪组织的分化和脂质合成影响很小，但即使在相似胴体重量下，较快的增重速度也会增加SC和PR脂肪组织的分化和脂质合成。
