Ewe fertility and neonatal lamb mortality

Abstract

Extract

The annual yield of lambs from a breeding flock is usually the major factor determining the success of a sheep farm. It is therefore surprising to find how many flocks are apparently reproclucing at a rate far below their genetic potential. There are many points at which the complicated and extended process of reproduction can be clistubed. Limiting factors fall into three main classes, (a) genetic limitations, (b) infective processes, (c) environmental factors (seasonal changes, environmental stresses and nutrition). At present knowledge of these influences is far from complete but it is most encouraging that research is being undertaken in many countries and progress is rapid. There is no reason to doubt that notable improvement could be made in many districts, but it must be stressed that it is difficult or even impossible to exploit all favourable influences; for example, the best time for mating may imply an unfavourable time for lambing or weaning; or market considerations may override physiological desiderata. It is obvious that in each district the pros and cons must be carefully weighed to select the most profitable combination of husbandry procedures; this can be clone rationally only on the basis of a great deal of knowledge.