THE decision whether to breed from ewe lambs is individual to each enterprise, but if there is a shortage of grazing or labour then it may not be a viable option, says vet Kythe Mackenzie, Westpoint Farm Vets, Penrith.
She adds the key to a profitable ewe lamb enterprise is using nutrition to allow good reproductive capability as well as growth.
“Ewe lambs need to be at 60 per cent of mature body weight at tupping to ensure success.
“Do not try and play catch up, as over feeding pre- and post-tupping will result in low lamb birth weight, decreased lamb vigour and decreased lamb survival. Ewe lambs use the feed for maternal weight gain and not placental development.
“Overfeeding to reach target weight will also result in poor udder development, with increased fat in the udder tissue causing decreased milk production. Ewe lambs should therefore be fed to achieve 75 per cent of maximum growth rate.”
From weaning to six weeks post-tupping (which should be a compact period following teaser rams) the aim is for the ewe lamb to gain about 250g per day, says Ms Mackenzie.
“This should result in good lamb development with some maternal growth and the birth of a single lamb, which is the ideal.
“To achieve this feed the dams 20 per cent more than adult ewes and provide excellent quality grass. If this is not available, supplement with concentrates at about 0.5kg per head per day.”
Into later pregnancy (six weeks pre-lambing) it is vital to feed to the number of foetuses. At this stage of nutrition the aim is to minimise foetal oversize so a decrease in daily liveweight gain should be expected.
“In late-pregnancy dry matter intake falls due to the size of the uterus, but ensure you feed a good source of digestible undegradable protein to maximise colostrum production and lamb vigour.
“To achieve this, the dams will require a low level of concentrates about 0.2 to 0.3kg/head/day [with all figures based on an average adult ewe weight of 80kg].”
Once lambed, the energy and protein requirements will increase to allow lactation without significant condition loss.
“A single lamb can be reared while allowing the dam to grow so she is fit to go back to the tup at 18 months of age.
“If she is feeding twins she needs significantly more energy, which will detract from her growth.
“During lactation a ewe lamb will require 20 per cent more feed than an adult ewe and needs an 18 per cent crude protein concentrate.
“The lambs should be creep fed from one-week-of-age and abruptly weaned at nine weeks, but certainly by 14 weeks to ensure the dams get maximum benefit from their feed and a chance to be in peak condition as shearlings.”
According to Novartis vet Matthew Colston, managing parasite burdens effectively is essential if the flock is to make best use of the nutrition available.
He says gastrointestinal worms and liver fluke are the two most common parasite problems for most farms, but require quite different approaches for effective control.
Sheep will generally mount an effective, protective immune response to gastrointestinal worms in response to exposure over the first one or two grazing seasons, so when it comes to managing worms in ewe lambs this has to be an important consideration.
“Suppressive dosing regimes [killing as many worms as often as possible] via frequent, repeated use of drenches or repeated use of persistent products can appear to give effective control in the short-term, but may leave some ewes without immunity to worms and therefore vulnerable to disease if faced with a worm challenge later on.”
For ewe lambs, Mr Colston says the best approach is to have a grazing management plan allowing for a low level, controlled exposure to parasites. This should be backed up with a programme to monitor worm burdens.
The opposite is true for liver fluke, says Mr Colston. The parasite affects both cattle and sheep, and neither species mount an effective, protective immune response to liver fluke.
“Minimising or eliminating exposure to the infective stages of the parasite is the aim, rather than controlled low level exposure,” he says.
“As liver fluke affects both cattle and sheep, any control measures for replacement ewe lambs have to be part of an overall ‘whole farm’ control plan.
"The key point for ewe lambs is to avoid exposure to the infected fluke cysts on pasture, as even low levels of liver fluke infection will have a negative impact on health.
"For this to be possible ‘safe’ or low risk areas have to be identified for the ewe lambs at high risk times of year (autumn and winter).
“Effective monitoring programmes can be set-up with little effort, which will show if/when ewe lambs meet a fluke challenge and allow the most effective use of the flukicides.
"Effective control of both GI worms and liver fluke rely on factors specific to the individual farm. One size does not fit all, so speaking to your vet or adviser to develop a plan specific to your own farm is the best approach to managing them in your replacement ewe lambs."
For more information see www.scops.org.uk and read George’s Journal on the National Sheep Association website.