Effects of melatonin implants on mating performance of Romney and
Poll Dorset rams
P.D. Muir, N.B. Smith, L.D. Staples
AgResearch, Hawkes Bay Agricultural Research Centre, P.O. Box 85,
Lawn Road, Hastings, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1993,
53: 275-280
The effect of melatonin (RegulinĘ) implants on the early season
performance of Romney and Poll Dorset rams was investigated in
experiments carried out over three consecutive years. In each experiment,
treated and untreated rams were introduced to groups of 100 or more ewes
which had been synchronised with CIDR's. Ram to ewe ratios ranged from
3.5% to 5.5%. In Experiment 1, melatonin treatment of Poll Dorset and
Romney rams prior to a January mating significantly improved ram
performance measured as the proportion of ewes mated (P<0.0001) but not
the proportion of ewes conceiving. In Experiment 2, untreated Romney rams
were already active at a January mating and melatonin treatment was found to
have no effect. In Experiment 3, there was a significant interaction between
ram breed and melatonin treatment in December but not in January or
February. Moreover, at the December mating, the more active ram groups
not only mated more ewes which were in oestrus, but also stimulated
significantly more CIDR treated ewes to ovulate. Since more active ram
groups stimulated more ewes to ovulate the results may explain the variation
in results obtained when CIDR's are used at an early season mating.
Keywords: NZSAPAB;
Rams; Poll Dorset; Romney; Regulin; melatonin.
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Last Updated 25-01-1997
