The overall aim of this project is to identify genetic markers for lamb survival. This paper reports the results from the first stage of the investigation aimed to identify the primary causes of lamb death from parturition to three days of age for highly fecund flocks. Flocks in the study consisted of 9 breeds and 12,000 breeding ewes and were located in New Zealand regions; Southland, Otago and Manawatu. All lambs were tagged and identified to their dam and sire. Lambs dead at birth and up to three days of age were collected (n = 1529), weighed, measured and examined by post mortem to determine cause and time of death. Primary causes of lamb death included: dystocia, starvation/exposure, amnion over nose, organ rupture, disease, and unknown. The mean mortality rate from birth to weaning for the 20 flocks studied was 14 ± 0.6% (SEM) in singles, 16 ± 0.3% in twins and 29 ± 0.6% in triplets. The study showed that the predominant primary cause of lamb deaths from parturition to three days of age was dystocia (difficult births). The dystocia rate was highest for dead single lambs (57 ± 4.2% SEM) (P < 0.05), where there was an unexpectedly high incidence for dystocia for dead twin (46 ± 1.7% SEM) and triplet lambs (48 ± 2.3% SEM). This suggests that dystocia as a primary cause of lamb death may be underestimated within highly fecund sheep flocks. The high death rate from dystocia in twin and triplet lambs has not been previously reported and is currently under further investigation. KEYWORDS: lamb survival; dystocia; post-mortem; cause of death; mortality; genetic; phenotypic.
Proceedings of the New Zealand Society of Animal Production, Volume 65, Christchurch, 13-18, 2005
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