Thermal Status in Three Breeds of Newborn Lambs during the First 24 Hours of Postnatal Life

1Institute of Mountain Stockreeding and Agriculture, BG -5600 Troyan, Bulgaria
2Institute of Animal Science, BG - 2230 Kostinbrod, Bulgaria
3Agrobioinstitute, BG - 1164 Sofia, Bulgaria


ALEKSIEV, Y., D. GUDEV and G. DIMOV, 2007. Thermal status in three breeds of newborn lambs during the first 24 hours of postnatal life. Bulg. J. Agric. Sci., 13: 563-573

Rectal temperature (RT) dynamics during the first 24 h after birth was studied in Pleven black head (PBH), Bulgarian fine wool (BFW) and Bulgarian fine wool x East-Friesian breed crosses (FC) lambs. Data were collected from a total of 137 lambs. For each breed group all lambs were paternal half sibs and born at term, without assistance. The ewes were housed in a sheep barn throughout the lambing period, which occurs in winter. Rectal temperature was recorded at 1, 3, 12, and 24 h after birth, within 0.1 °C. The newborn lambs were weighed within 1 h after birth. Skin fold thickness and fleece depth were measured on mid side. Time taken of each lamb until it first sucking was also recorded.
The lambs of the studied breeds had similar pattern of RT dynamics throughout the first 24 h after birth. Fall of RT was observed in all breeds up to 12 h postpartum followed by an increase at the 24th h. Bulgarian fine wool lambs had lower RT than the lambs of the other two breeds over the first day of postnatal life, but the difference was only significant at 1 h after birth (P<0.001). Lamb sex had no significant effect on the rate of RT decline during the first 12 h following birth. Single lambs had higher RT values at 1 h (P<0.01) and at 12 h (P<0.05) after birth than those in twins. Time to first sucking was similar in all breeds. In PBH lambs RT at 3, 12 and 24 h of postnatal life tended to be lower at ambient temperature 4.1 – 8.0 °C compared to that at 0.0 – 4.0 °C.
The results suggest that under prevailing management system and specific conditions in the barn the newborn lambs of the studied breeds were able to maintain successfully their body temperature at a range of ambient temperature 0.0 – 8.0 °C without any incidence of hypothermia.

Key words: breeds, lambs, newborn, rectal temperature dynamics
Abbreviations: RT = rectal temperature; PBH= Pleven black head breed; FC= Friesian crosses, BFW= Bulgarian fine wool breed

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