The effect of melatonin on the onset of first oestrus in Romney ewe lambs

R.W. Moore, C.M. Miller, P.R. Lynch; R.A.S. Welch, D.R. Barnes, H-U.P. Hockey

Whatawhata Hill Country Research Centre, Ministry of Agriculture and Fisheries, Hamilton; Ruakura Agricultural Research Centre, Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1984, 44: 21-24

Treatments were; no melatonin in 10 ml saline drenched daily (control), 2 mg melatonin in 10 ml saline drenched daily and 435 mg of melatonin implanted subcutaneously, each on 2 start dates - February 17 and March 17. Fertile rams were introduced on March 10 and April 7 respectively. All ewes were killed on July 28 and foetal crown-rump lengths measured to estimate the date of conception.

The mean dates of first tup in the early treatments were not statistically different (May 25, May 9 and May 13) but there was a difference between the control and implant in the estimated dates of conception (June 1 and May 17, P<0.05).

In the late treatment the mean dates of first tup were June 2, May 16 and May 10 respectively (P<0.01). However this difference did not lead to a treatment difference in the estimated date of conception because the percentages conceiving to the first tup were 38, 80 and 21 respectively.

Keywords: NZSAPAB;