Mortality rate of Boer, Central Highland goat and their crosses in Ethiopia: Nonparametric survival analysis and piecewise exponential model.

BACKGROUND: Analysis of survival data by linear or logistic model ignores censoring and skewness inherent in the mortality data. The objective of this study is to estimate the morbidity and mortality rates of kids and adult goats, identify important risk factors for mortality using survival analysis and summarise important causes of goat death. METHODS: Nonparametric survival analysis and a piecewise exponential model (PEM) were used. RESULTS: The mortality rates of kids and adult goats were 0.629 and 0.302 per animal year, respectively. The 25th, 50th and 75th percentiles of survival time of kids were 5, 162 and 1300 days, respectively, and those of adults and goats were 280, 828 and 1,735 days, respectively. Gastrointestinal-related diseases, pneumonia, weak kid, agalactia, mismothering and heartwater (cowdriosis) were the most important causes of mortality. Constant piecewise exponential regression analysis of risk factors indicated that breed, kid birth weight, doe post-partum weight (PPWT), birth type, birth year and precipitation variables were associated with (p-value < 0.05) kid mortality rate. Pure Boer kids compared with Central Highland goat cross with Boer goats were 2.505 times at a higher probability of mortality (p-value < 0.001). A 1-kg increase in kid birth weight and dam PPWT reduces mortality probability by 32.5% (p-value = 0.000) and 6.4% (p-value < 0.001), respectively. Twin birth kids had a 1.512 times higher rate of mortality (p-value = 0.001) than single-born kids. A 1-ml increment of 15 days of average precipitation significantly reduced kid mortality by 7.8% (p-value < 0.001). CONCLUSION: Vaccination, extensive control of ticks and the use of proper comfortable housing to reduce the stress of goats are recommended. Scheduling a mating programme (May to early July) to match the kidding period to the less kid mortality seasons (end of the long rainy season) of flocks is also important to reduce kid mortality.

Survival Analysis of Clinical Cases of Caseous Lymphadenitis of Goats in North Shoa, Ethiopia.

Caseous lymphadenitis (CLA) is a bacterial disease of small ruminants causing abscesses in lymph nodes of the body and internal organs. A longitudinal study from 2011 to 2019 was undertaken at Ataye site of Debre Birhan Research Center to estimate the prevalence and incidence, identify associated risk factors, and characterize the causative bacteria. 1025 goats were followed up for the CLA study. Survival analysis was done using SAS 9.4 software program. Biochemical tests and Biolog microbial identification system were used to characterize the bacteria. In the recurrent survival data analysis, there were 1,138 clinical observations and 214 CLA cases (18.8% prevalence) based on clinical diagnosis. The incidence rate was 0.14 cases per animal year. From a total of 214 cases, 130 have occurred once and 84 cases are recurrent cases following first cases. The cumulative failure rates were 68% for newborn and 64% for yearling age groups. The parotid lymph node was the most frequently affected site. Proportional hazard analysis results showed that sex, age, and breed were associated (p < 0.05) with CLA incidence. Females, newborn age group, Boer, and Boer × Central Highland Goat (CHG) were at higher risks compared to males, yearling age group, and CHG goats, respectively. The present study indicated that a high incidence rate of CLA in the goat farm is difficult to control and prevent because of its poor response to clinical treatment. Thus, control and prevention should focus on the spread of the disease such as isolation of clinically sick animals, culling, and vaccination of flocks.