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Beyond the Bale : September 2012
Once that's clear, the producer can investigate ways to overcome the problem. It is no good conceiving more lambs if lamb loss either through predation or ewe nutrition is the problem, he says. Equally, having ewe nutrition and predation spot on can only improve things so much if the ewes are not conceiving enough lambs. Dr Mike Rival says it's difficult to get hard data on the repeatability of multiple births because it's often skewed by seasonal conditions, but warns that it could be as low as 50 per cent. He suggests that pastoral producers in South Australia or NSW who join in November may experience lower fecundity (number of lambs born) than a similar mob structure joined in Autumn in Queensland. Dr Rival pregnancy tests up to 50,000 ewes a year in the eastern states and agrees with Mr Hickson that the focus should be on nutrition, scanning and condition score. He believes the Hickson system is simple and effective: 1. Scan maidens for pregnancy and cull ewes not in lamb -- at least during the initial or early years. 41 ON-FARM September 2012 BEYOND THE BALE So while it is very beneficial to put twin lambing ewes on the best feed available and have them in the best condition possible, it can actually be slightly detrimental to have single bearing ewes in too good condition. After scanning, twin bearing mothers go on to the best feed on the property -- native medic, lucerne or grazing oats, depending on what is available that year. If grass supply is limited, decisions are constantly made to adjust the stocking rate to match carrying capacity, and certain classes of stock are sold. Often the Hicksons find it is not feed quantity that is the problem, but quality. In those years, twin bearing ewes are supplemented with faba beans or grazed on the worst corners of grain crops to provide them with the massive amount of energy required to have and rear twins. Mr Hickson says being able to anticipate lamb numbers and match stocking rates with feed has been proven to have many benefits. In the severe drought year of 2007, the Hicksons, who normally run up to 15,000 DSE, had sold all their livestock except for 1700 of their core breeding ewes. These were sent to a nearby irrigator to put on his failed wheat crop. The result was 2300 lambs on the ground in good condition and a very small supplementary feeding bill. And the core breeding nucleus of Merino sheep was very much intact. Preferential feeding of twin bearing ewes during gestation can also largely overcome another challenge -- the fact that twin born lambs, due to lower secondary follicle density, have lower fleece weights and higher fibre diameters than single born lambs. In the past year, following information from the Lifetime Ewe Management program offered by Rural Industries Skill Training (RIST) and supported by AWI, the Hicksons have begun to concentrate on condition scores at weaning, joining, scanning and just prior to lambing, to ensure that ewes are in optimal condition to conceive and rear a lamb. Mr Hickson says if twin bearing ewes have a condition score of 3.5 to 4 at lambing, lambs are usually strong enough to withstand the vagaries of weather and predators. Last year helicopter contractors shot 480 pigs on Eural, with numbers boosted by good rains in the past two years. Foxes can be a problem and baiting is undertaken at times especially around the areas where twin bearing ewes are due to lamb. However, if the nutrition is right and lamb birth weights are up, foxes are less of a problem as the stronger lambs are more viable. In pastoral zones where flocks are larger, around 5000 ewes, Mr Hickson suggests scanning ewes on their second lambing and drafting off those with twins, to be given the best feed or supplemented in a hard season. These could be treated as twinning ewes for the rest of their life, meaning pastoralists only have to scan 20 per cent of their ewes each year. He cautions that this strategy will only work if the nutrition of the twinning mob is got right, otherwise after a tough year, the ewes will be less likely to conceive twins again as their condition score will be down from raising the previous lambs. He recommends scanning as the place to start investigating a flock's reproduction rate. By scanning, producers can find out whether getting their ewes in lamb is the problem or whether lamb survival is the problem. ewes for more lambs Dr Mike Rival pregnancy scanning ewes at 'Eural', NSW. Continued overleaf...