Generally, finer wool merino sheep are best suited to cooler areas Major Sheep Breeds In Australia Merino (75%) Border Leicester Merino x Border Leicester (12%) Suffolk Cheviot Poll Dorset Romney Merino Strains Strain Characteristics Adult Body Weight (kg) Fine and Superfine (Saxon) Medium Merino Strong Wool Lower body weight Lower fertility Lower fleece weight Includes both Peppin and non-peppin Most common sheep in Australia Devloped in the Riverina Micron range from 20-22 Often used in breeding first cross ewes South Australian type Higher bodyweight Higher preproduction 35-40 40-45 (fine) Fibre Diameter (microns) <19 19-20 (fine) 35-55 20-22 4-6 50-60 22+ 5-7 Greasy Fleece Weight (kg) 2-4 3-5 (fine) Main Factors Which Affect Sheep System Profits 1. Stocking Rates 2. Time of Lambing (and time of mating) 3. Supplementary Feeding Costs 4. Reproduction Rates (marking and weaning rates) 5. Wool and Meat Production per Head 6. Market Prices Stocking Rate Greater SR can often require a greater volume of supplementary feed o Reduce profits Lots of variation in farm profits with different stocking rates Need to cover risk
o Therefore, most farmers will be more conservative with stocking rates o Most farms operate under peak profit but with less variation and therefore less risk Production Targets (general) Meat: 100kg liveweight/ha per 100mm growing season rainfall Wool: 15kg greasy wool/ha per 100mm growing season rainfall Production Targets (Homes-Sackett)- Prime Lamb 1. 20kg dressed weight lamb sold/ha per 100 mm rainfall 2. 9 kg dressed lamb sold per DSE 3. 1 ewe joined/ha per 100mm rainfall 4. 120% lambs weaned per ewe joined 5. Lamb liveweight gain of 280g/day across the flock up to time of sale 6. Majority of lambs sold before pasture quality declines Key Management Decisions 1. Weaning and preparing ewes for the next year s joining 2. Linking ewe condition at joining with lambing potential 3. Pregnancy management and the impacts of ewe nutrition 4. Looking forward and planning for lambing- optimising lamb survival and future productivity 5. Setting up for joining in the second season- manipulating ewe condition and preparing rams 6. Economic analysis of different feeding strategies Reproduction Traditionally, ewes are first mated at 19 months In modern times, ewes are first mated at 8 months if the appropriate live weight has been met
o 5-month pregnancy + 3 month with lamb at foot + 4 month dry period before mating again The reproductive rate (both conception and the number of foetuses) of ewes is mainly affected by nutrition o Pre-joining nutrition affect ovulation rate o Mid-late pregnancy nutrition impacts lamb survival (particulary in cold conditions) and future performance of offspring o Early lactation nutrition affects milk production and therefore lam b growth rates and time taken to reach market liveweight o Nutrition around time of minimum fibre diameter impacts on wool staple strength Mothers of twins require up to 25MJ/day at peak of lactation cycle whilst mothers of singles only require up to 15MJ/day o Ideal to have twins if pasture availability is good as more liveweight=more profit The energy demand of the reproducing lamb is met with a late winter lambing time o Pasture does not provide adequate nutrition during most late summers and some level of supplementary feeding is usually required Time of Lambing Most important management decision Choosing a time of lambing for feed base can be influenced by: 1. The ewe s natural breeding season
2. The pasture supply throughout the year and matching it to peak energy demand of the ewes 3. Date of lamb turnoff for slaughter and target weight targets Prime lamb flocks will often lamb 4-5 months before the end of the reliable growing season to give a better result as it maximises the chance of finishing the lambs on pasture (cheapest source of energy and protein) Self-replacing Merino flocks often lamb 3-4 months before the end of the reliable growing season Joining Time of joining: Oestrus activity in ewe increase after the longest day of the year o As the day length shortens, cycling activity increases to peak between March and May when most ewes are cycling and with higher ovulation rates Decisions around ewe and ram health and nutrition should be made prior to joining Seasonal breeders o Merinos and poll dorsets least affected by day length o Border Leicesters and other British Breeds are most affected by day length Ram Effect: Ewes can be stimulated to cycle by the introduction of males prior to the natural mating season o Teaser rams can be introduced to assist in inducing oestrus and help manipulate the time of breeding o Ewes often have a silent oestrus and will therefore have to cycle again before falling pregnant o For this reason, teasing ewes 14 days prior to joining rams in recommended when joining before February Ewe preparation o Check ewes condition at least one month prior to joining to asses if feeding is required to maintain condition Check 25-50 sheep from middle of the mob
o Check ewes for low condition, udders, poor feet and mouth condition (cull from flock) o Ewes should be in 3+ condition score Good cover of muscle and fat over the short ribs o Tease ewes if mating prior to mid-jan o Join for 35 days (equivalent to two cycles) Condition Score and Ewe Performance The higher the CS of the ewes at joining, the higher the potential number of lambs and lower number of dry ewes in a flock o Average response is an extra 20 lambs per 100 ewes for an additional CS at joining The higher reproductive rate is due to fewer dry ewes and more ewes conceiving twins At condition score 3, there should be no more than 10% dry ewes in most Merino flocks and less than 5% dry ewes in cross bred flocks At condition score 3, around half of the lambs born will be twins Ideal to reduce the number of unproductive ewes to improve reproductive efficiency in the system Most of the wool follicle development occurs in the second and third trimesters and can be significantly affected by nutrition Also need to consider vaccination and worm control to maintain good health (and therefore CS) Optimal birthweights are from 4-6kg and a decrease in condition score of ewes during pregnancy can reduce lamb birthweight by 0.4-0.5kg 15-20% more lambs survive when born to ewes above CS of 2.3 Twin survival is doubled compared to that of a single lamb survival with better conditions during pregnancy Additionally, ewes in better condition have less mortality during late pregnancy Split Lambing Lambing early in winter leaves sheep exposed to lack of pasture if rain is late Lambing late in winter gives better pasture growth but less time to grow lambs before pasture growth ends