Wind chill index and neonatal lamb mortality at an organized farm in semi-arid Rajasthan

Abstract

Using climatic data from 1991 to 2016 recorded at Avikanagar, wind chill index (WCI) was calculated for each day during winter (December–February) coinciding with major lambing season. The WCI (kcal/m2/h) was categorized as no chill (<300.0), low (<300.1–350.0), moderate (350.1–400.0), high (400.1–450.0) and extreme (>450.1) and the neonatal lambs death (857) in a total of 2257 days (December–February of each year) were considered to observe the effect of WCI. The overall annual neonatal lamb mortality was 5.85%. Over the years daily WCI revealed a significant increase in number of extreme chill days (WCI > 400.1 kcal/m2/h) since December 2003. The overall proportion of neonatal death ranged from 2.10% (WCI < 300 kcal/m2/h) to 69.34% ((WCI > 400.1 kcal/m2/h). The climatic data showed that out of total days, majority of days (64.99%) covered were of high to extreme chill in nature (WCI > 400.1 kcal/m2/h). The daily rate of neonatal mortality found to possess a positive and linear relation with WCI and ranged from 0.25 lamb death/day (WCI < 300 kcal/m2/h) to 0.46 lamb death/day (WCI > 450.1 kcal/m2/h). The entities responsible for exposure-inanition syndrome (EIS, debility, exposure, inanition) had positive relation with WCI. The contribution of EIS in overall neonatal mortality ranged from 29.08 (WCI 300.1–350.0 kcal/m2/h) to 42.00% (WCI > 450.1 kcal/m2/h). The analysis suggested requirement of proper shelter management for neonatal lambs during extreme climate.