George J M
Aust Vet J. 1975 May;51(5):262-5. doi: 10.1111/j.1751-0813.1975.tb06931.x.
The mean incidence of dystocia in 1,510 fine-wool Merino ewes over a ten-year period was 4.1% of ewes lambing. In the 10 year period, 10% of all neonatal mortality was attributed to dystocia and in only 23% of dystocias was lamb presentation abnormal. The incidence of dystocia was not related to age of ewe. Significantly more ewes experienced dystocia at spring than winter (P less than 0.05) or summer (P less than 0.01) lambings. The mean birth weights of dystocic single and twin born lambs were 4.19 and 3.38 kg respectively. The corresponding birth weights of lambs that did not experience dystocia were 3.69 and 3.00 kg. More ewes experienced dystocia when stocked at 12 or 16 per ha than at 8 per ha (P less than 0.05). Fifty per cent of recorded dystocias occurred in ewes stocked at 16 per ha, 40 per cent at 12 per ha and 10 per cent at 8 per ha. Ewe body weight pre-lambing was not related to the incidence of dystocia but it would appear that weaker ewes are more likely to have a difficult birth than ewes that are stronger and in better condition.
在十年期间，1510只细毛美利奴母羊难产的平均发生率为产羔母羊的4.1%。在这十年中，所有新生儿死亡的10%归因于难产，且仅23%的难产病例胎位异常。难产发生率与母羊年龄无关。春季产羔的母羊发生难产的情况显著多于冬季（P<0.05）或夏季（P<0.01）产羔的母羊。难产情况下单胎和双胎羔羊的平均出生体重分别为4.19千克和3.38千克。未发生难产的羔羊相应出生体重分别为3.69千克和3.00千克。每公顷饲养12只或16只母羊时，发生难产的母羊比每公顷饲养8只时更多（P<0.05）。记录的难产病例中，50%发生在每公顷饲养16只母羊的情况下，40%发生在每公顷饲养12只的情况下，10%发生在每公顷饲养8只的情况下。产羔前母羊体重与难产发生率无关，但看起来较弱的母羊比更强壮、状况更好的母羊更有可能难产。
