Andrews A H
Vet Q. 1981 Jan;3(1):9-18. doi: 10.1080/01652176.1981.9693788.
The development of the mandibular cheek teeth was examined, both visually and by radiograph, in a group of 76 Hereford cross Friesian steers, of which all but one were slaughtered at the same weight - 464 kg (1020lb). The age of the youngest animal was 1 year 0.3 months whereas the slaughter ages of the others ranged from 1 year 3 months to 1 year 8 months. The first molar was fully erupted and crown and root formation complete in all but the youngest steer. In the other five cheek teeth there were one or more significant differences between the mean ages of tooth development stages as assessed by radiograph. Cattle of 1 year 3 months could not be absolutely distinguished from those of 1 year 8 months by intra-oral second molar eruption. Examination of stages of development seen radiographically gave a maximum age range of 4 months before differentiation. In this study, development of the first two molars was in advance of the three permanent premolars and in these latter teeth the second premolar was the most developed.
对一组76头赫里福德与弗里斯兰杂交阉牛的下颌颊齿发育情况进行了视觉和X光检查。除一头牛外，其余所有牛均在体重达到464千克（1020磅）时屠宰。最年幼的动物年龄为1岁零0.3个月，而其他牛的屠宰年龄在1岁3个月至1岁8个月之间。除最年幼的阉牛外，第一磨牙均已完全萌出，牙冠和牙根形成完整。通过X光评估，在其他五颗颊齿的牙齿发育阶段平均年龄之间存在一个或多个显著差异。仅通过口腔内第二磨牙的萌出情况，无法绝对区分1岁3个月的牛和1岁8个月的牛。通过X光检查牙齿发育阶段发现，在分化前的最大年龄范围为4个月。在本研究中，前两颗磨牙的发育先于三颗恒前磨牙，且在这些后一组牙齿中，第二前磨牙发育最为充分。
