Journal Articles

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    The Effect of Age of Dam and Birth Rank on the Reproductive Performance of Ewes as One- and Two-Year-Olds.
    (10/03/2021) Pettigrew E; Hickson R; Morris S; Kenyon P; Corner-Thomas R; Haslin E; Blair H
    Currently, 30-43% of New Zealand sheep farmers breed their ewe lambs, but few retain the offspring as replacements for their flock. No difference in lamb production as a yearling among singletons and twins born to ewe lambs and twins born to mature ewes has been reported, provided the ewe lambs had reached the 60-65% of their likely mature weight prior to breeding at seven to eight months of age. The aim of this experiment was to determine the lamb production from singletons and twins born to ewe lambs and twins born to mature ewes during their first two years of lambing. The experiment included 8-month-old ewes born as twins to mature ewes (M2, n = 135), singletons born to ewe lambs (L1, n = 135), and twins born to ewe lambs (L2, n = 88), bred during the same period to the same rams, over two years. The efficiency of lamb production (total litter weight at weaning divided by the pre-breeding weight of the ewe, for all ewes presented for breeding) after two years of production was not significantly different (p > 0.05) among the groups (0.40 ± 0.02, 0.39 ± 0.02, and 0.39 ± 0.03, for M2, L1, and L2, respectively).
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    Reproductive performance of singleton and twin female offspring born to ewe-lamb dams and mature adult dams
    (New Zealand Society of Animal Production, 7/07/2016) Loureiro, MFP; Kenyon, PR; Pain, SJ; Blair, HT
    This study was undertaken to compare the reproductive and live weight performance of female singleton and twin ewes born to either mature or young dams from 18 months to 2.5 years of age. One hundred and fifteen singleton- and twin-born female offspring born to either ewe-lamb (8 months at breeding) or adult ewe dams were maintained as one cohort under commercial New Zealand grazing conditions. Ewe live weights and body condition scores were recorded, as were ovulation rates at a synchronised breeding and number of fetuses present at pregnancy scanning. The live weight of ewes born to ewe-lambs were lighter (P<0.05) than those born to adult ewes at breeding and during their first pregnancy but not (P>0.05) at the weaning of their lambs. Twin-born ewes were lighter (P<0.05) than their singleton-born counterparts. There was no difference in corpora lutea number (P>0.05) at breeding or number of fetuses at pregnancy scanning. Lambs whose grand dam was a ewe-lamb were heavier at birth (P<0.05) but not at weaning (P>0.05) compared to those lambs whose grand dams was an adult ewe. This data suggests there are few negative impacts from selecting progeny born to ewe lambs as replacement ewes. However, before this hypothesis can be supported, lifetime data of these ewes needs to be collected.