Matched groups of ewe hoggets were mated to either fertile Southdown rams or vasectomised rams for a 6-week period in 1980 and 1981. The percentage of Romney, Coopworth and Perendale hoggets born in 1979 showing oestrus were 82, 92 and 92, and for those born in 1980 47, 84 and 79 respectively. The lower incidence of oestrus in those born on 1980 can be partly explained by lower hogget pre-lambing weights related to an outbreak of facial eczema in April 1981. Of hoggets joined to fertile rams, the percentages that weaned a lamb were 47, 60 and 67 for those born in 1979, and 13, 53 and 52 for those born in 1980. The percentages of two-tooths joined that weaned a lamb (average for those born in 1979 and 1980) were 71 for those not tupped as hoggets, 74 for those tupped by vasectomised rams, 53 for those tupped by fertile rams but not lambing, and 76 for those lambing as hoggets. There was no suggestion that hogget lambing impaired two-tooth reproduction, but those lambing produced 0.15 kg less wool at the two-tooth pre-mating shearing. The April 1981 GGT level of the 1980-born ewes was inversely related to live weight in April through to September 1981, and to percentage of ewes lambing as hoggets and as two-tooths, and to two-tooth pre-mating fleece weight.
Proceedings of the New Zealand Society of Animal Production, Volume 43, , 13-16, 1983
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