Year-round lamb production in the Manawatu region - results from year one

Abstract

Four hundred and eighty East Friesian composite (50% East Friesian, 25% Poll Dorset, 25% Texel) or Romney ewes were assigned to either a conventional lambing (March) group or a year-round lambing group. The trial began in January 2003 and the year-round system aims to have ewes lambing every 73 days. In the year-round system approximately a third of the ewes were synchronised and joined with mixed age rams of their respective breed for a 21 day period on 13 January, 27 March, 8 June, 21 August and 1 November. This results in each ewe having the opportunity to lamb five times in a three-year period. The conventionally bred ewes were joined with rams on 27 March for 2 cycles of breeding. Results after year one indicate the number of lambs born and weaned per ewe lambing was similar for East Friesian ewes in the year-round and conventional lambing groups. However Romney ewes reared less lambs (1.22 vs 1.41, P<0.05) than East Friesian composite ewes in the conventional system. Pregnancy rates at scanning were higher in East Friesian composite than Romney ewes in the year-round system (0.75 vs 0.65, P<0.05) but there were no differences between the two breeds in the conventional system. Lamb birth weights were heavier in the conventional system than the year-round system (5.1 ± 0.1 kg vs 4.2 ± 0.1 kg and 4.8 ± 0.1 kg vs 4.1 ± 0.1 kg for East Friesian and Romney ewes respectively). Lambs born in June were significantly lighter than lambs born in August or November in the all year-round system. Lamb growth rates and weaning weights of lambs born to East Friesian composite dams were heavier than lambs born to Romney dam in both systems. The major constraint that appears to be limiting high performance in the year-round system is the low pregnancy rates in the non-breeding season (i.e. August to January). Based on year one data it can be concluded that income from lamb sales in the year-round system can match or better (in the case of East Friesian composite ewes) a conventional March lambing system without any premiums for the out-of-season lambs and is likely to be further improved if pregnancy rates can be improved. Keywords: lamb growth, lamb production, number of lambs born, year-round lambing