McLeod K R, Baldwin R L
USDA, ARS, Livestock and Poultry Sciences Institute, Nutrient Conservation and Metabolism Laboratory, Beltsville, MD 20705, USA.
J Anim Sci. 2000 Mar;78(3):760-70. doi: 10.2527/2000.783760x.
We used 28 crossbred wether lambs to determine the effects of dietary forage:concentrate ratio and metabolizable energy intake on visceral organ growth and oxidative capacity of gut tissues in lambs. Lambs were assigned randomly to a factorial arrangement of dietary treatments consisting of pelleted diets containing either 75% orchardgrass or 75% concentrate fed once daily at either .099 or .181 Mcal ME x (kg BW(.75))(-1) x d(-1). After a 52-d feeding period, lambs were slaughtered to obtain measurements of visceral organ mass and composition and oxidative capacity of isolated epithelial cells. Lamb performance, as measured by DMI, ADG, and efficiency of gain, was greater (P = .0001) for both diets at high ME intake. Likewise, lambs fed 75% concentrate gained faster and more (P < or = .01) efficiently than lambs fed 75% forage. Total digestive tract (TDT; includes rumen, reticulum, omasum, abomasum, and intestines) weight increased (P = .0001) with ME intake and was greater (P = .03) in lambs fed 75% forage than in those fed 75% concentrate. As a percentage of empty body weight (EBW), TDT weight increased with ME intake in lambs fed 75% forage, but it was unaffected by ME intake in lambs fed 75% concentrate (diet x intake, P = .03). Liver weight increased (P = .0001) with ME intake and was greater (P = .005) in lambs fed 75% concentrate vs 75% forage; however, liver weight as a percentage of EBW was increased (P = .0002) with ME intake but was unaffected by diet. Greater ME intake increased (P < or = .02) small intestinal (SI) epithelial and muscle mass of 15-cm sections, whereas jejunal epithelial mass was greater (P = .01) for lambs fed 75% forage vs 75% concentrate. Rumen epithelial concentrations of DNA and RNA increased (P < or = .02) with greater ME intake, whereas SI concentrations of DNA and RNA were largely unaffected by diet or ME intake. The activity of Na(+)-K(+)-ATPase increased in ileal epithelium (P < or = .02) with ME intake and concentrate in the diet, but activity in ruminal epithelium increased (P = .05) with concentrate. Total oxygen consumption by isolated ruminal and intestinal epithelial cells was unaffected by treatment. These data suggest that ME intake and level of dietary forage affect ruminal and intestinal growth via changes in cellular hyperplasia. Additionally, this study supports the concept that ME intake and diet composition alter gut energy expenditure, at least in part, through changes in mass rather than mass specific metabolism.
我们使用28只杂交去势公羔羊来确定日粮中粗饲料与精饲料比例以及代谢能摄入量对羔羊内脏器官生长和肠道组织氧化能力的影响。将羔羊随机分配到日粮处理的析因设计中，日粮处理由颗粒饲料组成，分别含有75%的果园草或75%的精饲料，每天以0.099或0.181兆卡代谢能×(千克体重(0.75))(-1)×天(-1)的量投喂一次。经过52天的饲养期后，宰杀羔羊以获取内脏器官质量、组成以及分离的上皮细胞氧化能力的测量值。以干物质采食量、平均日增重和增重效率衡量的羔羊生长性能，在高代谢能摄入量时两种日粮下均更高(P = 0.0001)。同样，采食75%精饲料的羔羊比采食75%粗饲料的羔羊增重更快且更高效(P≤0.01)。总消化道(包括瘤胃、网胃、瓣胃、皱胃和肠道)重量随代谢能摄入量增加(P = 0.0001)，采食75%粗饲料的羔羊总消化道重量高于采食75%精饲料的羔羊(P = 0.03)。作为空腹体重的百分比，采食75%粗饲料的羔羊总消化道重量随代谢能摄入量增加，而采食75%精饲料的羔羊则不受代谢能摄入量影响(日粮×摄入量，P = 0.03)。肝脏重量随代谢能摄入量增加(P = 0.0001)，采食75%精饲料的羔羊肝脏重量高于采食75%粗饲料的羔羊(P = 0.005)；然而，肝脏重量作为空腹体重的百分比随代谢能摄入量增加(P = 0.0002)，但不受日粮影响。较高的代谢能摄入量增加了(P≤0.02)15厘米肠段的小肠上皮和肌肉质量，而采食75%粗饲料的羔羊空肠上皮质量高于采食75%精饲料的羔羊(P = 0.01)。瘤胃上皮中DNA和RNA浓度随代谢能摄入量增加(P≤0.02)，而小肠中DNA和RNA浓度在很大程度上不受日粮或代谢能摄入量影响。回肠上皮中Na(+)-K(+)-ATP酶活性随代谢能摄入量和日粮中精饲料增加(P≤0.02)，但瘤胃上皮中该酶活性随精饲料增加(P = 0.05)。分离的瘤胃和肠上皮细胞的总耗氧量不受处理影响。这些数据表明，代谢能摄入量和日粮粗饲料水平通过细胞增生变化影响瘤胃和肠道生长。此外，本研究支持这样的观点，即代谢能摄入量和日粮组成至少部分通过质量变化而非质量比代谢改变肠道能量消耗。
