A NOTE ON MORTALITY OF SOCORRO ISLAND MERINO LAMBS

Abstract

Background. The Socorro Island Merino sheep constitutes a unique population in the world whose number is reduced to less than a hundred individuals, thus facing an imminent risk of extinction. Objective. The objective of this study was to analyze the causes and risk factors associated with the mortality of Socorro Island Merino lambs. Methodology. The rate and causes of mortality were determined and the association between mortality and weight, year of birth, sex, genotype of the lamb and the number of lambing of the ewe was determined by Chi-square test. Subsequently, a logistic regression analysis was performed using only those variables significantly associated with mortality. Results. Mortality rate was 29.31%. The 70.59% of deaths occurred during the first 48 hours after lambing being starvation the main cause of death. Mortality was associated (P<0.05) with the lambs’ year birth and the number of lambing of the ewe, while birth weight, sex and genotype were not related (P>0.05) with death of the lambs. According to the logistic regression analysis, lambs born in 2020 and born to a multiparous ewe had an 83 and 74% lower risk of death than those born in 2019 and to a primiparous ewe, respectively. Implications. The use of professionally qualified personnel and the establishment of good zootechnical management practices significantly reduces lamb mortality. Conclusions. Starvation represented the main cause of death, while the year of birth of the lamb and the number of lambing of the ewe were the risk factors associated with mortality.