Year round lambing, Massey University

September 2006
New Zealand lamb production is driven by the seasonal pattern of pasture growth, resulting in an inconsistent supply of lamb for slaughter. Yet, international lamb markets require a consistent supply of product throughout the year.

Year-round lambing would better service international market demand, make more efficient use of processing facilities, and could offer 12-month employment to skilled people in the meat processing industry.

The year-round lambing trial is funded under Meat & Wool New Zealands R&D strategy for High Performance Sheep Systems. This aims to increase sheep productivity by 4% per year by targeting the national weaning percentage, lamb growth rate, optimising system efficiency and meeting market specifications.

The Massey trial

The Massey trial began in January, 2003 and ended this year. The final drop of lambs was born in June and weaned on August 21. Year-round lambing will continue on the Massey farm, as a commercial operation.

Four hundred and eighty mixed-aged ewes comprising equal numbers of East Friesian composite (50% East Friesian, 25% Poll Dorset, 25% Texel) and Romney were used in the trial.

Half were assigned to a year-round lambing group and further split into three mobs. At each breeding period, ewes were synchronised then joined with mixed age rams of their respective breed for a 21-day period on January 14, March 28, June 9, August 21 and November 2. Progesterone-primed intravaginal devices (CIDRs) were used to synchronise oestrus at all five matings. Ovulation was induced using PMSG.

The other half of the ewes were joined with rams on March 28 each year and no reproductive hormones were used.

Lambs in the year-round system were weaned at 73 days after the planned start of lambing and were finished off the unit.

Each flock was managed on a separate 20 hectare area.

The results

The East Friesian composite performed better in the year-round system than the Romney, producing an extra 1880kg of lambs weaning weight (versus 88kg) with a similar number of lambs born and weaned under the two regimes.

For East Friesian composite ewes, the extra lamb production generated by year-round lambing would pay for induction and synchronisation costs, says Massey Associate Professor Steve Morris who oversaw the trial with hands-on help from PhD scholar Gina deNicolo. However, this would not be the case for Romney-type ewes.

The extra kilograms of lamb produced from year-round lambing reflects a greater number of ewe matings (934 vs 478) and a higher number of lambs weaned (772 vs 553) than in the once-a-year system.

The limiting factor was low out-of-season pregnancy rates, which were higher in the once-a-year flock (90.9-99.1% vs 55.3-75.7%).

Year-round lambing did not compromise ewe live weight at mating or two weeks prior to lambing. Average daily weight gains in lambs were better in the year-round system.

Uptake on farm

Relevance of the trial on farm was ensured by the involvement of a farmer mentor group, as was required by trial funding body Meat & Wool New Zealand.

Already, a farm in Hawkes Bay is experimenting with year-round lambing without the use of hormones. A Southland property is using the Dorset Horn breed to trial three lambings in two years, rather than five lambings in three. There is also strong interest from farmers with milking sheep, looking for consistent yearly supply of milk.

The system will not be applicable to summer-dry areas or places with extremely cold winters due to the pattern of pasture growth.

It will be relevant on the West Coast of the North Island and maybe on irrigated areas elsewhere, and on properties with crop reside, Morris suggests.

Results will be communicated to farmers via an R&D brief to be published through Meat & Wool New Zealand.