Drafting lambs: Draft lambs for slaughter as soon as they become ‘fit’.
Lambs can be drafted from as low as 40 kg live weight early in the season as kill-out percentages tend to be higher. This is particularly the case for young, creep fed lambs which can kill out as high as 50%. Kill-out percentage can be as low as 42-44% for lambs fed only grass later in the season. Bear in mind carcase weight limits of individual factories and aim to draft lambs before they become too heavy. However it is equally important to have adequate fat cover on lambs. Ensure withdrawal dates of any anthelmintic treatments or other animal medicines used are observed.
Aim to wean lambs at 12-14 weeks of age. Target the best quality grass to lambs. Ewes in good condition can be used as followers to graze poorer quality swards. After eight to ten weeks of age the contribution of milk to the overall diet of lambs is minimal. Early weaning at ten weeks of age is an option for hogget ewes, especially if body condition is poor. It may seem a long time until the next breeding season but remember it could take ten to 12 weeks for a ewe to gain one body condition score (BCS). A rule of thumb is that one BCS is equivalent to 12 kg of live weight and ewes on good grass can gain 1.0 kg of live weight per week.
Warm, damp conditions provide the ideal environment for blueflies and maggot strike. A darkening of the wool at the site of attack is the common primary sign of bluefly attack, with wool loss in the more advanced stage. Closely monitor lambs in particular and decide on appropriate preventative treatments as some provide a longer period of protection than others. Traditional dipping, pour-ons and showering are the main options. Pay particular attention to the withdrawal periods on these products as some are relatively long and will not suit heavier lambs closer to finishing.
Continue to monitor worm burdens
Monitor worm burdens in both cattle and sheep. Damp, warm conditions can increase worm burdens. Mixed grazing of cattle and sheep reduces their individual worm challenge as the worms infecting cattle are different to those infecting sheep. Burdens will increase as calves and lambs become more reliant on grazed grass. Dairy bred beef calves are particularly susceptible due to their higher grass intakes from an earlier age compared to suckler bred calves. A leader-follower system also reduces burdens on young stock.
If first cut silage has not been harvested yet assess the crop regularly. Strike a balance between silage quality and yield. A later harvest date generally leads to higher yields but poorer grass quality. Target a silage dry matter of 30% and a D-value greater than 70. This can be achieved by harvesting before a lot of seed emergence occurs and ensuring a good rapid wilt. A concern sometimes is that nitrate may still be present in the grass, particularly if fertiliser spreading was late, as this can negatively affect silage fermentation. A rule of thumb is that two units of nitrogen per acre is used up by the crop daily. Therefore if three 50 kg bags of CAN (27% N) was spread this equates to 81 units of nitrogen. This would take just under six weeks to be used up. It is important to note that this is just a general guide, the rate will be higher during periods of high growth and lower in periods of poorer grass growth. Any nitrate present in grass at harvesting is less of an issue where a good wilt has been achieved.