Norton J H, Tranter W P, Campbell R S, Shepherd R K
Queensland Department of Primary Industries, Oonoonba Veterinary Laboratory, Townsville.
Aust Vet J. 1989 Jun;66(6):167-70. doi: 10.1111/j.1751-0813.1989.tb09793.x.
An association with a rank correlation of 0.55 (p = 0.06) was obtained between monthly rainfall and monthly abortions for a group of 24 farms in tropical Australia where cows grazed predominantly summer rain-dependent pasture. A similar association was found among cows grazing nitrogen-fertilised, irrigated pasture in winter in the same area. On farms with irrigated pasture the first service conception and abortion rates in herds which grazed intensively during the night (abortion 8.9%; first service conception 42.9%) differed significantly from those which grazed during the day (abortion 6.4%; first service conception 52.9%), and this suggested that increased abortion rates and decreased first conception rates may be part of the one syndrome. An hypothesis was developed that the feeding of immature nitrogen-fertilised pasture, rich in protein and stimulated by rain or irrigation, is associated with an increased abortion rate and a depressed conception rate. Other evidence included an increased susceptibility of first lactation cows to abortion, a lower abortion rate in late pregnant dry cows fed more mature pasture, a 20% repeat abortion rate in the population sampled and the lack of conclusive evidence for infectious and selected non-infectious agents. There were no other observed clinical signs in most aborting cows.
在澳大利亚热带地区的24个农场中，牛主要采食依赖夏季降雨的牧场，研究发现月降雨量与月流产率之间存在等级相关性为0.55（p = 0.06）的关联。在同一地区冬季放牧于施氮肥灌溉牧场的奶牛中也发现了类似的关联。在有灌溉牧场的农场中，夜间 intensive 放牧的牛群（流产率8.9%；首次配种受胎率42.9%）的首次配种受胎率和流产率与白天放牧的牛群（流产率6.4%；首次配种受胎率52.9%）有显著差异，这表明流产率增加和首次受胎率降低可能是同一综合征的一部分。由此提出一个假说，即采食富含蛋白质、受雨水或灌溉刺激生长的未成熟施氮肥牧场，与流产率增加和受胎率降低有关。其他证据包括头胎奶牛流产易感性增加、采食更成熟牧场的妊娠后期干奶牛流产率较低、抽样群体中20%的重复流产率以及缺乏感染性和特定非感染性因素的确凿证据。大多数流产奶牛没有观察到其他临床症状。 （注：原文中“grazed intensively”的“intensively”翻译可能不准确，需结合语境进一步确定准确含义）
