Observations on neonatal progress of Dormer and South African Mutton Merino lambs

Author: S.W.P. Cloete
Year: 1993
Issue: 2
Volume: 23
Page: 38 - 42

Data of Dormer (n = 290) and SA Mutton Merino (n = 306) lambs, born by ewes which were observed continuously during lambing in 1989-1991, formed the basis of this investigation. Progeny of SA Mutton Merino ewes were heavier at birth (P 0.05) than progeny of Dormers in 1989 and 1990, but no difference was observed in 1991. Lambs given birth to by maiden ewes (2 years) were slower (P 0.01) to stand than progeny of adult (3-6 years) and old (7 years) ewes. A significant interaction between dam age and birth type was observed with regard to progress from standing to first suckling. Single lambs born to maiden ewes responded slower (P 0.05) than multiples. Amongst the progeny of mature ewes, singles progressed faster (P 0.05) than multiples, and a similar tendency was observed in progeny of old ewes. Time-lapses from birth to standing and from standing to apparently suckling declined (P 0.01) with an increase in birth mass. Halfsib analysis of variance heritability estimates were 0.46 ± 0.16 for the interval from birth to standing and 0.22 ± 0.12 for the interval from standing to suckling. Lambs which died subsequently were slower (P 0.01) to stand, and tended (P = 0.07) to progress more slowly from standing to suckling than their contemporaries which survived. It is doubtful whether these results will find application in practice, since such observations are very labour-intensive. From a scientific viewpoint it is important to take cognisance of the possibility of genetic variation in neonatal progress, suggesting that selection may have a role to play in the reduction of lamb mortality. Live-mass gain to ca. 3 days of age was found to be a reliable indicator of subsequent lamb mortality in twin and triplet lambs. An increase of 1 kg was associated with decreases of 22% in twin mortality and 43% in triplet mortality.



Keywords: birth mass, neonatel lamb progress, survival
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