Lambing time is here for many people and although we strive for ‘easy care’ systems; surveillance of lambing paddocks is essential for animal welfare. Picking up dead lambs and ewes controls disease and predators and gives good information on prevalence of problems eg mastitis. Keeping records of losses and reasons for these losses, when known, provides invaluable information for flock productivity in the future.
Try to assess the liveweight of single and twin lambs to see if they are adequate, in relation to ewe weight and the climatic conditions and nutrition over pregnancy. Lamb liveweight is strongly associated with lamb survival rates, lambs of good birthweight have more energy stored as fat reserves and so are better equipped to survive starvation, wet and windy conditions, and will maintain their suckling drive longer than low birthweight lambs. Aim for birthweights of 4-5kg. Low birthweight lambs are usually born to ewes in poor condition and these ewes will require preferential feeding if they are to feed their lambs adequately. Underweight ewes can still feed their lambs as long as they are given top quality feed, and ewes in good condition can milk ‘off their backs’. But they can’t do both ie an underweight ewe cannot be expected to feed her lambs from her body reserves if she doesn’t have any!
Remember the best liveweight gain per day will be achieved between birth and weaning. The onset of lactation and colostrum production are affected by ewe nutrition in late pregnancy, whilst feeding during lactation influences total milk production. Daily milk production peaks at 2-3 weeks after lambing, and then gradually declines. The ewe uses dietary energy (ME) and her own body reserves for milk production in early lactation, regardless of the level of feeding, and particularly in ewes rearing twins. The ewe normally replaces some of these losses (mainly fat and muscle) during the second half of lactation. However due to the high cost of replacing body tissue, weight losses during pregnancy and lactation should be minimised.
Ewes with twins produce 30-50% more milk than singles, but as this is shared between 2 lambs, each lamb only receives two thirds as much milk as a single lamb. To make up for this lower milk consumption, twin lambs are forced to start eating pasture at an earlier age than singles. Peak production has been measured at around 2.3litres/day for a single suckled ewe and 3.5litres/day for twins, and 40%-50% of total milk is produced in the first 4 weeks of lactation.
During lactation to ensure milk supply and avoid excessive weight loss, it is recommended that ewes are offered 6-8kg green DM/day to ensure that they eat 2-3kg DM/day. Remember this means 10-15kg fresh grass and this requires covers of 1500-2000kg DM/Ha (approx. 5-7cm height).
