JUNE 2018 www.irishfarmersmonthly.com Sheep Focus Dosing yield by week eight is only 50 per cent of its peak. By week 12, it is considerably less. Therefore, lambs at 12-14 weeks are getting practically all their feed from grass and very little from milk. Ewes turn to foe for lambs at this time of year. They produce little milk and compete with their lambs for grass. The lambs are better weaned at this stage. At 12-14 weeks, a ewe requires 2-2.5kg of dry matter (DM) and each lamb requires over 1kg each. Lambs are selective grazers, picking the sweetest and best grass for themselves. If the ewes are with them at week 14, then this intake of 1kg is not possible. When to wean Cobalt solution may be purchased or home-mixed. • 10-15ml/lamb is administered depending on the concentration of cobalt sulphate, which contains 21 per cent cobalt. Dose lambs as frequently as possible, ideally at two-week intervals. Longer intervals will give very poor responses; •  A combination of cobalt and vitamin B12 gives immediate B12 and the cobalt necessary to enable the lamb to produce its own supply of B12; •  Do not mix the cobalt mixture with a worm drench, as mixing will not be uniform. Some worm drenches contain added cobalt, however the quantity is usually insufficient in deficiency situations. Other minerals, eg. copper and selenium, may also be required. Supplementation of these must be based on herbage and blood analysis. June can be a ‘crunch’ month as far as lamb thrive is concerned. Attention to detail, especially in grazing management, can make the difference as to whether that crunch will take the form of expensive meal to shore up lack of quality grass. The recommended practice is to wean at 12-14 weeks. A farm where the ram goes out in mid-October and lambing commences in early-to-mid-March reaches 12 weeks in early June and 14 weeks in late June. Do not allow lambs go more than 14 weeks. Being able to supply adequate grass to lambs is the key to successful weaning. If grass is scarce for the ewe, then it is very scarce for the lambs. Early weaning should then be considered to allow lambs have the best. After weaning lambs will eat over 1kg of grass DM. In trials where 1.5kg was offered, the lambs were forced to eat practically all the grass available. This lowered growth rates to less than 0.6kg/week. Where this grass is not available on farms, the gap is often filled with creep to prevent lambs stalling and going into a store period. Lambs offered 5kg of DM/day could selectively graze the sward. This gave gains of over 1kg/ week. Offering 5kg/day is equivalent to 8-9cm of grass in a set stocking situation. Do not graze tighter than 6cm with rotational grazing. Allowing lambs to selectively graze ryegrass/clover swards will give gains of over 1.5kg/week. Identify fields with high clover content and close for weaned lambs. Cobalt on deficient farms Some soils are naturally low in cobalt. Other soils are high in manganese, which ties up cobalt, making it unavailable to grazing animals. Lambs in mid-summer will be the first animals to show signs of cobalt deficiency. Take action now; otherwise, lamb growth will suffer. Cobalt is not directly required by the lamb. It is needed by the rumen microbes to manufacture vitamin B12. This vitamin is then absorbed by the lamb. Where the rumen microbes are denied cobalt, vitamin B12 will not be produced. Lambs will not thrive, will lose condition and wool will dry out. Cobalt is normally supplied after weaning but it may be beneficial pre-weaning on some farms. In a perfect world, cobalt should be given every day as lambs cannot build up a store of cobalt in the rumen. 41