New Zealand Journal of Agricultural Research abstracts

Ewe reproduction and lambing performance in a five period mating system

G. deNicolo

S. T. Morris*

P. R. Kenyon

P. D. Kemp

P. C. H. Morel

College of Sciences
Massey University
Private Bag 11222
Palmerston North 4442, New Zealand

*Author for correspondence:

S.T.Morris@massey.ac.nz

Abstract Ewe reproduction and lamb performance in two breeds (East Friesian Composite (EF) and Romney) was assessed at five different breeding and lambing periods within a year, including three aseasonal breeding periods, over a 3-year period. The experiment was designed so that weaning coincided with the first day of each synchronised breeding period. In addition to intravaginal progesterone, eCG was used for aseasonal breeding periods (January, August, November). Pregnancy rates in March (EF; 94%, Romney; 91%) and June (EF; 91%, Romney; 91%) were higher than August (EF; 54%, Romney; 45%), November (EF; 49%, Romney; 41%) and January (EF; 68%, Romney; 39%; P < 0.001). Number of lambs born and weaned per ewe lambed was highest for August-bred EF and March-bred Romney ewes, and varied within and between years. November-born lambs were heaviest at birth and had the lowest mortality, and March-born lambs were the lightest at birth (P < 0.05). Lambs born to EF ewes were heavier than Romney lambs (P < 0.05). August-born lambs were heaviest at weaning and grew faster from birth to weaning than lambs born in other lambing periods. This experiment demonstrated that for either an accelerated or an out-of-season lamb production system to be successful, low out-of-season pregnancy rates need to be addressed.

Keywords accelerated lambing system; aseasonal breeding periods; eCG; pregnancy rates; progesterone; reproduction; sheep

A07172; Online publication date 30 September 2008
Received 27 August 2007; accepted 8 September 2008

New Zealand Journal of Agricultural Research, 2008, Vol. 51:397–407
0028–8233/08/5104–0397 © The Royal Society of New Zealand 2008

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