Ho L, Field R A, Russell W C, Riley M L, Ercanbrack S K, Williams F L
University of Wyoming, Laramie 82071.
J Anim Sci. 1989 Sep;67(9):2460-70. doi: 10.2527/jas1989.6792460x.
Fifty-one ewes, 50 wethers and 51 rams of Finn x whiteface or Suffolk x whiteface breeding were slaughtered at an average age of 271, 361, 459, 557 or 652 d to study changes in maturity characteristics with changes in age. When metacarpal epiphyseal cartilage (growth plates) ossifies with age, break joints on the distal end of the metacarpals fuse and the end of the bone then appears as a spool joint rather than as a break joint. This fusion occurs earlier chronologically in ewes than in rams or wethers. Most Finn x whiteface-cross ewes, which normally reach reproductive maturity earlier than Suffolk x whiteface-cross ewes, exhibited ossified metacarpal growth plates by 459 d of age; break joints of Suffolk x whiteface crosses were not fused until 557 d of age. Both breed groups of rams exhibited fused joints by 557 d of age, but only 3 of 10 wethers exhibited spool joints at 652 d of age. Microscopic examination showed that even in these three wethers the epiphyseal growth plate could still be detected. Yearling 2-yr-old classifications of sheep from teeth were not gender-dependent within the discrete age classes of this study. About half the sheep in each gender group were classified as yearlings at 459 d of age and about half in each group were classified as 2-yr-olds by 652 d of age. Stepwise multiple regression equations to estimate age of sheep in days were developed. Overall maturity, lean color and texture and rib bone maturity were the best carcass measures of maturity. Maturity scores for characteristics of the break joint did not enter any of the equations studied. When eye lens weight was included in equations with the best measures of carcass maturity, accuracy of estimates for age of sheep was improved.
选取51只芬兰×白面或萨福克×白面杂交繁育的母羊、50只阉羊和51只公羊，分别在平均年龄271、361、459、557或652日龄时屠宰，以研究成熟特征随年龄变化的情况。随着年龄增长，掌骨骨骺软骨（生长板）会发生骨化，掌骨远端的断关节融合，此时骨头末端呈现为卷轴关节而非断关节。这种融合按时间顺序在母羊中比在公羊或阉羊中更早发生。大多数芬兰×白面杂交母羊通常比萨福克×白面杂交母羊更早达到生殖成熟，在459日龄时就表现出掌骨生长板骨化；萨福克×白面杂交羊的断关节直到557日龄才融合。两个品种组的公羊在557日龄时都表现出关节融合，但10只阉羊中只有3只在652日龄时呈现卷轴关节。显微镜检查表明，即使在这三只阉羊中，仍能检测到骨骺生长板。在本研究的离散年龄组内，根据牙齿对一岁和两岁绵羊的分类与性别无关。每个性别组中约一半的羊在459日龄时被分类为一岁羊，到652日龄时，每个组中约一半被分类为两岁羊。建立了逐步多元回归方程来估计绵羊的日龄。整体成熟度、瘦肉颜色和质地以及肋骨成熟度是胴体成熟度的最佳衡量指标。断关节特征的成熟度评分未纳入所研究的任何方程。当将眼球晶状体重量纳入具有最佳胴体成熟度衡量指标的方程中时，绵羊年龄估计的准确性得到了提高。
