What are the two types of life tables used in veterinary epidemiology?

• A. Cohort (generation) life table.
• B. Cohort (generation) life table and current (period) life table.
• C. Current (period) life table.
• D. Cross-sectional life table.

Answer: (B)

Life tables summarize how survival or mortality changes with age in a population. In veterinary epidemiology, two main forms are used: a cohort (generation) life table and a current (period) life table. A cohort life table follows a defined birth cohort through time, recording deaths as they occur and calculating age-specific mortality and survival for that particular group as it ages. This approach tells the actual experience of that cohort, but it needs long follow-up and complete follow-up data.

A current (period) life table uses data from a cross-sectional snapshot in a single time period to estimate age-specific mortality rates and survival, essentially applying those rates to a hypothetical cohort to describe mortality conditions for that period. It’s quicker and useful when follow-up data aren’t available or you want a timely picture, but it reflects the mortality conditions of that specific time rather than the experience of a specific birth cohort.

Cross-sectional life table is not a separate type; it’s the form used to construct a current (period) life table from a single-time snapshot. So the two types you’d typically encounter are the cohort life table and the current (period) life table.