Effect of weather on conception rates of sheep

During the spring of 1970 a number of farmers in Hawke`s Bay observed that they had more dry-dry ewes than usual in their flocks or that two distinct peaks had occurred in their lambing pattern. Possible explanations for this situation included weather fluctuations, either directly or through factors dependent on them, excess amounts of subterranean clover or disease. After investigation the two latter suggestions were discarded. To investigate the events of the autumn of 1970, detailed mating records were sought and on one property accurate records had been kept of 2550 ewes mated to raddled rams…