Parturition and neonatal behaviour data of Dormer and SA Mutton Merino lambs were recorded during 1992-1996. Single and first-bom multiple SA Mutton Merino lambs were heavier (P < 0.05) at birth, and had longer (P < 0.01) parturitions. Dormer lambs were less (P < 0.05) likely to die during or shortly after birth than SA Mutton Merinos (0.035 vs 0.067; Chi2 = 6.14). Relative to the total phenotypic variation, the magnitude of direct additive effects (h2 ± SE) was of the same magnitude as that of maternal permanent environmental effects (c2) for birth weight (0.22 ± 0.09 and 0.19 ± 0.04 respectively). Direct additive effects were relatively unimportant for length of parturition (0.02 ± 0.04) but c2 effects were important (0.17 ± 0.03). Dormer lambs were respectively 22 and 40% slower (P < 0.01) to progress from birth to standing and from standing to apparently suckling than SA Mutton Merinos. Post partum deaths within 3 days of birth was more (P = 0.06) prevalent in Dormer lambs than in SA Mutton Merinos (0.042 vs 0.022; Chi2 = 3.52). The time lapse from birth to first standing was equally influenced by h2 and c2 effects (0.10 ± 0.05 and 0.09 ± 0.04 respectively). In the case of the period from standing to first suckling, h2 effects were less important than c2 effects (0.07 ± 0.04 and 0.19 ± 0.04 respectively). The c2 effects are probably related to maternal behaviour in the neonatal phase, and will include intensive and persistent grooming of the neonate, co-operation with its first suckling attempts, the absence of aggression and aspects like teat placement and size. A better understanding of the inheritance of behaviour traits conducive to lamb survival will assist in the formulation of a sound breeding strategy for sheep.

S. WP Cloete, J. J Olivier, A. J Scholtz

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 27: Reproduction; fish breeding; genetics and the environment; genetics in agricultural systems; disease resistance; animal welf, , 39–42, 1998
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