ChileanJAR

A report is made on a five year study (1960-1964) conducted at the Cauquenes Experimental Sub-Station of the Instituto de Investigaciones Agropecuarias (Cauquenes, Chile), on some of the factors affecting sheep fertility, such as age at time of lambing, body weight as an expression of size, breeding age, and genetic effects through the differences observed in three breeds: German Merino, French Merino and Suffolk Down. Ages of the animals at time of lambing varied betwen two and eight years. The highest lambing percentage occurred at six years of age in German Merino, at four to six years of age in French Merino, and at five years of age in Suffolk Down. The percentage of animals born with respect to those bred, gave no significant differences for any of the ages of the three breeds under consideration. vVeight of ewes at first lambing indicated that the heavier ewes tend to give birth to twins in a higher proportion than lighter ewes. Times of breeding tried (beginning of January ami middle of February) gave no significant differences for any of the years under study, although the times closest to Fall gave the highest rates of lambs born, especially in the Suffolk Down breed. German Merino had the highest lambing percentage, although the differences were not significant for any of the years under study. It is estimated that the prevailing idea that Downs are more fertile than Merinos is based on the fact that the former are bred under better conditions than the latter. These differences would disappear if they were compared under favorable conditions.