Epidemiological and Aetiopathological Investigations on Neonatal Lamb Mortality

Abstract

This study was conducted on pregnant Pak-Karakul (n=525) and Thalli (n=412) ewes and their lambs (528,423, respectively) born at Sheep and Goat Development Centre, Rakh Khairewala, District Layyah during the parturition season 1998-99. Blood sampling with and without anticoagulant was made at pre- and post-lambing periods from ewes and blood samples of neonates were taken 24-36 hours post-lambing. Hematological, biochemical and physical parameters were recorded and correlated with neonatal lamb mortality. Neonatal lamb mortality was recorded to be 9.28 and 12.06% in Pak-Karakul and Thalli neonatal lambs, respectively. In Pak-Karakul lambs, pneumonia rendered highest morbidity and mortality and all mortalities recorded were in the first week of life whereas in Thalli lambs diarrhea was at peak and 82.35% mortalities were recorded in the first week of life and 17.65% mortalities in the second week of life. Chilling and mis-mothering was not observed in Pak-karakul lambs and parrot mouth in Thalli lambs. Parity of the ewes and sex of neonatal lambs in both the breeds did not effect mortality rates whereas birth weight of neonates, those died was significantly (P<0.001) lower than those survived. Male had more birth weight than females in both the breeds. Hematological parameters showed non-significant effect on mortality but the neonates those died had low values of TEC, PCV, Hb and erythrocytic indices except MCV. Neonates those survived had higher values of TLC than those died. Lambs with lgs level less than 20 ZST-units died and neonates with >20 ZST-units survived. Dams those lost their lambs had low values (12.11+1.97; 14.13+2.55 g/L) of colostral lgs than those with live neonates (15.81+3.72; 18.43+10.14 g/L). It was interesting to note that enzymic concentration in the dams has relation with the neonatal lamb mortality. AST and AP level at pre- and post-lambing stage in the dams whose lambs survived was significantly (P<0.05) low compared with the dams whose lambs died. However, ALT at the post-lambing stage between the dams of survived and died lambs did not differ significantly. Birth weight was negatively correlated with age of the dam (r=-0.052). Birth weight of lamb showed positive correlation with TEC (r=0.055), PCV (r=0.153), Hb (r=0.160), TLC (r=0.262), lymphocytes (r=0.089), monocytes (r=0.115), total proteins (r=0.303), albumin (r=0.028), globulins (r=0.256) and serum lgs (r=0.451). there was negative correlation (r=-0.531) between sex and birth weight of neonates. TEC, PCV, Hb, TLC, neutrophils, lymphocytes, eosinophils, total proteins, albumin, globulins and serum lgs showed negative correlation in survived and died neonates. Colostral lgs were negatively correlated with age of the dam. Neonates died of diarrhea of either breed exhibited lesions in the small intestine in the form of congestion and hemorrhages. Lesions were in wide spread distribution both involving small and large intestine. In the neonates died of pneumonia, trachea contained moderate to excessive amount of frothy exudate to copious amount occluding lumen. Lungs were moderate to severely congested and contained froth. Microscopically in neonates those did of diarrhea, sections of the intestine revealed congestion, pneumonia, the alveolar capillaries were dilated and studded with erythrocytes. Congestion and oedema of alveoli, alveolar septa were observed. Inflammatory cells including neutrophils followed by mononuclear cells were seen in the alveolar walls forming the walls thickened.