Parturition difficulties in sheep

Abstract

The incidence of difficult parturition was recorded in Texel Sheep lambs (224), Milk Sheep lambs (273) and various crossbreeds (1043) in ten spring lambing seasons. at lambing time the ewes were under 24-hour observation.

Difficult parturition is defined as necessity for obstetrical assistance as a result of failure of expulsion or progress within a given time limit.

The course of parturition was recorded on a standard protocol. Shortly after parturition ewes and lambs were weighted and several body measurements of the lambs were taken.

In this first report of the study, special attention is given to the influence of presentation of the lambs at birth. Presentation type is divided into four categories:

• - stretched: upright cranial presentation with forelegs stretched in all joints (nose of lamb at upper end of metacarpus) • - shoulder-elbow flexion: upright cranial presentation with flexion of forelegs in shoulder and elbow (nose of lamb at the hooves) • - various abnormal cranial presentations • - posterior presentations Records from 1540 lambs became available. For 284 (18.4%) presentation was unknown, partly due to rapid delivery. Stretched presentation was observed in 172 (11.2%) lambs. No lambs in this category needed assistance at birth. Shoulder-elbow flexion occurred in 707 (45.9%) lambs, of which 36.9% needed assistance. The incidence as well as need of assistance in this presentation increased rapidly with birthweight of the lamb. Various abnormal cranial presentations were noted in 289 (18.8%) lambs, 50.9% needed assistance. Posterior presentation was seen in 88 (5.7%) lambs, of which 64.13% needed assistance at birth.

For the statistical analysis of the data a stepwise logistic regression analysis was used. The significant factors influencing the incidence of difficult parturition in this study were in order of decreasing importance: (1) presentation of lamb, (2) birthweight, (3) number of lambs per ewe, (4) genetic type or breed, (5) parity of the ewe, (6) birthweight– presentation interaction, (7) genotype–presentation interaction, (8) sex of lamb.

The distinction between stretched and shoulder-elbow flexion presentation is discussed and related to results of other investigations. It is concluded that cranial presentation with forelegs stretched in all joints is the most optimal (however infrequent) presentation.