Risk factor analysis for neonatal lamb mortality at an organized farm of arid Rajasthan

The comparative neonatal mortality (NM) profile in Magra and Marwari sheep was studied to assess the influence and magnitude of different non-genetic risk factors (odds ratio, OR) using data on 8650 lambs (4768 Marwari and 3882 Magra) born from April, 2000 to March, 2016 at Arid Region Campus (ARC), Bikaner, Rajasthan. Overall annual NM was 1.79%. The NM increased with advancement of age of lambs (0.18% during 0 to1 day-old to 0.52% during 4 to 7 days-old) in Marwari lambs. Significantly (P<0.001) 2 to 4 times higher NM was observed in Marwari lambs as compared to Magra lambs. In comparison to lambs of >3.50 kg birth weight, the OR varied from 1.3 (3.01 to 3.50 kg birth weight) to 9.5 (up to 2.00 kg birth weight). In comparison to lambs of >3.50 kg birth weight, >30-times higher risk for death due to septicaemia was observed in lambs up to 2.00 kg body weight. Lambs with poor body weight were at 6 times higher risk for enteritis. An inverse relation was observed between magnitude of overall neonatal mortality and age of dam at lambing. Irrespective of breeds, the overall NM was significantly (P<0.001) affected by parity of dam with higher mortality in lambs born to primiparous ewes. Relatively higher risk (2 times) was observed for overall and cause specific NM in lambs born to ewes in their first parity compared to those in 3 ^rd parity. Dam's weight at lambing showed U-pattern for NM with maximum mortality in lambs born to ewes with <28.0 kg body weight particularly during hebdomadal phase. The NM was significantly (P<0.001) 2 times higher in the lamb to dam weight ratio of <0.100 compared to those with ratio of >0.100. Season of lambing generally had non-significant effect on neonatal mortality in both the breeds. The causes of neonatal lamb mortality were pneumonia (32.90%) in total deaths followed by septicaemia/toxaemia (23.23%), enteritis (14.84%) and tetanus (7.74%). The study revealed that sheep flocks at ARC, Bikaner had higher neonatal mortality during early phase of life, primarily due to lower birth weight of lamb. Better management should be adopted for proper nursing of lambs with low birth weight particularly born to primiparous ewes.