Comerford J W, House R B, Harpster H W, Henning W R, Cooper J B
Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802.
J Anim Sci. 1992 Apr;70(4):1022-31. doi: 10.2527/1992.7041022x.
Fifty-eight Holstein and 58 crossbred beef steers were individually fed one of four isonitrogenous diets to evaluate the effects of forage source (corn silage and alfalfa haylage) and protein source (soybean meal and fish meal) on feedlot performance. Phase 1 diets (up to 354 kg of BW) were 40% forage and 60% concentrates and were fed for 70 to 136 d (depending on diet and breed group). Phase 2 diets (354 kg of BW until slaughter) were 20% forage and 80% concentrates and were fed for 127 to 150 d (depending on diet and breed group). Slaughter end points were .6 cm of 12th rib fat for Holsteins and 1.0 cm of rib fat for crossbreds using real-time ultrasonic estimates. The steers were fed for a maximum of 330 d each year. Forage source was a significant component of variation for most growth, efficiency, and carcass traits. Holstein and crossbred steers fed alfalfa haylage had significantly lower average daily gain, feed efficiency, dressing percentage, and empty body fat and required more days on feed to reach slaughter end points, but had higher total feed energy intake available for production. Steers fed corn silage diets had significantly greater energetic efficiency (P less than .05) than those fed alfalfa haylage, due to increased use of ME to produce fat in the carcass. Protein type did not influence gain, feed or energetic efficiency, energy intake, or most carcass traits. A significant protein system x forage source interaction among the four diets was detected for crossbred steers fed corn silage and fish meal, for which there was significantly greater feed conversion with lower energy intake above maintenance, possibly due to better fiber digestion and(or) amino acid flow to the lower tract. Alfalfa haylage plus soybean meal diets decreased (P less than .05) the percentage of Holsteins grading USDA Choice or higher. These results indicate that corn silage, because of greater energy concentration, was a more desirable forage in feedlot diets composed of less than or equal to 40% forage and that protein type (soybean meal and fish meal) in growing diets is not an important factor in feedlot performance or carcass traits of Holstein or crossbred steers that are fed these diets.
选取58头荷斯坦牛和58头杂交肉牛公牛，分别给它们饲喂四种等氮日粮中的一种，以评估饲草来源（玉米青贮和苜蓿青贮）和蛋白质来源（豆粕和鱼粉）对育肥性能的影响。第一阶段日粮（体重达到354千克之前）含40%的饲草和60%的精饲料，饲喂70至136天（取决于日粮和品种组）。第二阶段日粮（体重从354千克到屠宰）含20%的饲草和80%的精饲料，饲喂127至150天（取决于日粮和品种组）。屠宰终点为使用实时超声测定，荷斯坦牛第12肋骨处脂肪厚度达0.6厘米，杂交肉牛为1.0厘米。这些公牛每年最多饲喂330天。对于大多数生长、效率和胴体性状而言，饲草来源是变异的一个重要组成部分。饲喂苜蓿青贮的荷斯坦牛和杂交肉牛公牛平均日增重、饲料效率、屠宰率和胴体脂肪显著较低，且需要更多的饲喂天数才能达到屠宰终点，但用于生产的总饲料能量摄入量较高。由于胴体中用于产脂的代谢能利用增加，饲喂玉米青贮日粮的公牛能量效率显著更高（P<0.05）。蛋白质类型对生长速度、饲料或能量效率、能量摄入量或大多数胴体性状没有影响。在饲喂玉米青贮和鱼粉的杂交肉牛公牛的四种日粮中，检测到显著的蛋白质体系×饲草来源交互作用，对于该日粮，维持以上能量摄入量较低时饲料转化率显著更高，这可能是由于纤维消化更好和（或）氨基酸向下消化道的流动更好。苜蓿青贮加豆粕日粮降低了（P<0.05）评定为美国农业部精选级及以上的荷斯坦牛的比例。这些结果表明，由于能量浓度更高，在由不超过40%饲草组成的育肥日粮中，玉米青贮是更理想的饲草，并且在生长日粮中蛋白质类型（豆粕和鱼粉）对于饲喂这些日粮的荷斯坦牛或杂交肉牛公牛的育肥性能或胴体性状而言不是一个重要因素。
