Notter D R, Kelly R F, McClaugherty F S
Dept. of Anim. Sci., Virginia Polytechnic Institute and State University, Blacksburg 24061.
J Anim Sci. 1991 Jan;69(1):22-33. doi: 10.2527/1991.69122x.
Lamb growth, survival and carcass characteristics were compared for progeny of either 1/2-Suffolk, 1/2-Rambouillet (Western) ewes or 1/2-Suffolk, 1/4-Rambouillet, 1/4-Finnsheep (1/4-Finn) ewes produced over 3 yr in three different management systems. System 1 lambs were born in late fall and fed to slaughter on a concentrate diet. System 2 lambs were born in January and February and grazed pure stands of alfalfa or ladino clover after weaning. System 3 lambs were born in March and April and remained with their dams on native bluegrass-white clover pasture throughout the grazing season. Lambs were slaughtered as males reached 55 kg and as females reached 50 kg. One-half of the males in System 1 were left intact; all males in Systems 2 and 3 were castrated. Lamb survival did not differ among systems. Lambs from yearling 1/4-Finn ewes had higher survival rates than lambs from yearling Western ewes, but at older ewe ages, progeny of the ewe groups did not differ in survival. Lambs in System 1 grew fastest (mean lifetime gains of 310 +/- 4 g/d) and were youngest at slaughter (156 +/- 3 d), and lambs in System 3 were oldest at slaughter (234 +/- 2 d). System 2 lambs differed considerably among years in growth rate and slaughter age (mean slaughter ages of 191, 230 and 193 d across years), primarily in response to differences in rainfall. Lifetime gains and slaughter ages of lambs did not differ between ewe breeds. Ram lambs grew 15% faster than wethers and were leaner. Differences among systems in carcass traits were small. System 1 lambs tended to be fattest and System 2 lambs leanest. Progeny of 1/4-Finn ewes had higher subjective scores for carcass fatness (e.g., feathering, flank fatness) and conformation but did not differ from progeny of Western ewes in objective measures of fatness (e.g., backfat, yield grade).
在三种不同的管理系统下，对三年间所产的1/2萨福克、1/2兰布耶（西部）母羊或1/2萨福克、1/4兰布耶、1/4芬兰羊（1/4芬兰）母羊的后代的羔羊生长、存活和胴体特征进行了比较。系统1的羔羊在深秋出生，以精饲料育肥至屠宰。系统2的羔羊在1月和2月出生，断奶后在苜蓿或拉地诺三叶草纯种牧场上放牧。系统3的羔羊在3月和4月出生，在整个放牧季节与母羊一起留在原生早熟禾-白三叶牧场上。当雄性羔羊达到55千克、雌性羔羊达到50千克时进行屠宰。系统1中一半的雄性羔羊未去势；系统2和3中的所有雄性羔羊都被阉割。各系统间羔羊的存活率没有差异。一岁龄1/4芬兰母羊所产羔羊的存活率高于一岁龄西部母羊所产羔羊，但在母羊年龄较大时，两组母羊的后代在存活率上没有差异。系统1中的羔羊生长最快（平均终生日增重310±4克），屠宰时最年轻（156±3天），系统3中的羔羊屠宰时最老（234±2天）。系统2的羔羊在不同年份间生长速度和屠宰年龄差异很大（各年份平均屠宰年龄分别为191、230和193天），主要是由于降雨量不同。羔羊的终生日增重和屠宰年龄在母羊品种间没有差异。公羊羔羊比阉羊生长快15%，且更瘦。各系统间胴体性状的差异较小。系统1的羔羊往往最肥，系统2的羔羊最瘦。1/4芬兰母羊的后代在胴体脂肪度（如被毛、肋腹脂肪度）和体型方面的主观评分较高，但在脂肪度的客观测量指标（如背膘厚、产肉等级）上与西部母羊的后代没有差异。
