Causes of perinatal lamb mortality amongst Dormer and SA Mutton Merino lambs

Perinatal lamb deaths were investigated in Dormer (n = 290) and SA Mutton Merino (n = 306) progeny born to 166 and 147 ewes respectively. Causes of mortality were investigated by autopsy in 30 Dormer and 61 SA Mutton Merino lambs that died during the perinatal period. Perinatal lamb deaths were higher (P < or = 0.01) in SA Mutton Merino lambs than in Dormers (0.199 vs 0.103). Anteparturient deaths (APD) were confined almost exclusively to triplet lambs, and contributed 10-12% of the overall perinatal lamb mortalities in both breeds. This category was closely associated with prolonged parturition, with 86% of the 7 ewes involved needing assistance after more than 4 h. The majority of parturient deaths (PD) were associated with stressful births, which contributed a higher (P < or = 0.05) proportion of total perinatal deaths in SA Mutton Merino lambs than in Dormers (0.508 vs 0.267). Ewes giving birth to litters consisting of one or more lambs in the birth stressed PD or birth stressed post parturient death (PPD) categories (also including APD deaths because of their obvious relationship to prolonged births), furthermore had longer (P < or = 0.05) parturitions than contemporaries that lost one or more lambs as a result of other causes, or ewes that reared all lambs born through the perinatal period (214 vs 98 and 74 min respectively). Uncomplicated starvation/mismothering/exposure (SME) syndromes mostly contributed to the PPD category, and constituted 21-27% of perinatal lamb deaths in the 2 breeds. Deaths with clinical signs of SME could mainly be related to udder malfunction, which was observed in nearly 60% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)