Improving Lamb Survival And Growth Rates

(condensed from a presentation by Dr. Annette Litherland, AgResearch, Palmerston North)

Maximising the lambing percentage and lamb growth can substantially lift farming profitability.

Every farmer understands that, yet many sheep farmers seem to have problems in matching the desired end product and his/her particular farming system.

  1. Improving lamb survival
  2. Pre-weaning lamb growth rates
  3. Post-weaning lamb growth rates
  4. Increasing summer feed quality
  5. Canterbury Farmlet Studies

1. Improving lamb survival

What is your level?

As the number of twins increase, lamb survival can be expected to decrease slightly.

Research established these average figures from scanning results:

Scanning percentage:120140160180
% lamb loss:16171819

If your lamb losses are greater than these figures, work down the list and eliminate potential risks:

Inadequate vaccination programme

Protect lambs from clostridial diseases by vaccinating ewes with "5 in 1". If warranted, use Toxovax to improve lamb survival. Campylobacter abortions can be prevented by vaccinating with Campyloxvexin.

Poor mineral status

In selenium deficient areas, ewes should be injected with a supplement at mating and two weeks prior to lambing.

Look for sub clinical iodine deficiency if healthy born lambs die for no obvious reason. This is also possible when brassica crops have been fed during winter without iodine supplementation. Ask your vet for help since iodine deficiency can vary between years.

Underweight or overweight lambs at birth

If low lamb weights are a consistent problem, shear (use winter comb) twin bearing ewes at mid pregnancy (70 to 100 days pregnant) as this can increase twin lamb birth weights by 0.5 kg. Prevent extreme weight loss of ewes during pregnancy (up to 4 kg) as this can reduce twin lamb size by 0.4 kg.

A terminal sire crossed with highly fecund ewes will increase lamb survival due to increased birth weights and heterosis.

Steep slopes, poor shelter and disturbance

Bad weather can have a profound effect on lamb survival. You can increase lamb survival by giving the highest risk group the best paddocks. The ewes with the greatest risk of lamb loss are those bearing triplets, followed by young twin bearing ewes, then twinning mixed aged ewes, and so on.

Ewes like to select birth sites with a clear view, and so often lamb at the top of slopes and exposed ridges.

In the case of twin lambs ewes might not always leave the birth site to follow a lamb falling down a slope. Streams, swamps, exposed ridges etc. are potential death traps in stormy weather.

Shelter improves lamb survival, but shelter that prevents the ewe from seeing her lamb may prevent the ewe looking for the lamb. Often slopes in the lee of the prevailing storm can provide shelter.

Avoid disturbing lambing ewes since this can cause mismothering. Try to avoid lambing in paddocks you have to drive through every day. Ewes will move larger distances in flat paddocks than on steeper hills.

Poor maternal traits in the ewe

Some breeds of sheep show better mothering ability than others. Younger ewes have less developed maternal instincts than older ewes (incidentally, Coopworth's usually display a very strong maternal instinct - ed)

Poor ewe condition and nutrition

Ewes that are well fed before lambing have less clinical and sub clinical sleepy sickness, produce more colostrum and milk, have stronger lambs, and bond better with their lambs. In late pregnancy fetal growth is very rapid and the ewe has high feed requirements. For ewes bearing singles, feed requirements are 29% higher, twins 52% and triplets 73%, compared with a dry ewe two weeks before lambing.

At lambing, single carrying ewes should be set stocked at 1000 kg DM/ha and twins at 1200-1500 kg DM, depending on the lambing date. If feed is going to be short, keep ewes tight at the early stages of pregnancy rather than later.

It is unlikely that twin bearing ewes will increase their condition over the last few weeks before lambing.

Triplet ewes can not eat enough to meet the requirements over late pregnancy, and a new high protein supplement has shown some promising results in survival of triplets (G. Davis, AgResearch Invermay)

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2. Pre-Weaning Lamb Growth Rates

Actual measurements of lamb growth rates from birth to weaning on several North and South Island farms revealed:

Feeding ewes during lactation

Pasture quality declines by late October due to rising temperatures and longer days. The graph below shows the actual measured values of pasture growth rates for dry, southern North Island farms.

To adequately feed ewes in early lactation and insure good pasture quality in late lactation, the lambing date needs to be judiciously timed.

Improved pasture management in spring, to better match supply and demand, offers potential lamb growth rates of 300 to 350 g/day. This provides a 100 day weaning weight of around 35 kg.

Allocation of feed to ewes

Ewes won't milk well if they are in poor condition at lambing and/or underfed during lactation.

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3. Post - Weaning Lamb Growth Rates

Pasture quantity and lamb growth rate

The goal of 400 grams/day lamb growth rates remains just that for many farmers - a goal. In reality maximum growth rates for weaned lambs is more like 340 g/day on very high quality forages fed at very high allowances.

Most lambs show much slower live weight gains.

Pasture quality and sheep performance

Pasture quality facts:

  1. The most important nutritional limitation for sheep is insufficient metabolisable energy (ME) intake.
  2. Fungal toxins (Facial Eczema, Fusarium, grass staggers) will reduce ewe reproductive performance and lamb weight gain.
  3. Contamination with parasite larvae reduces quality (energy is needed to fight the challenge)
  4. Trace elements can also be a problem - consult your vet.

Pasture components vary in quality

Quality declines with age

Diet selection and feed quality


  1. Dead matter substantially reduces the quality of diet
  2. In high dead matter pastures, shift lambs more frequently to maximise their available selection
  3. Predominantly grass pastures grown in high temperatures have lower quality
  4. Predominantly grass pastures grown in high temperatures and grazed for long periods have markedly lower quality

So what constitutes high quality pasture?

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4. Increasing Feed Quality In Summer

Control pastures in spring:

Grow lambs faster pre-weaning

This reduces the requirements for a high quality feed in summer.

Plant alternative forage crops

Reasons for alternatives to ryegrass:

If you want to increase feed quality by using a crop it should:

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5. Canterbury Farmlet Studies

(Tom Fraser, AgResearch Lincoln)

System: 12 ewes/ha, mid August lambing, mid November weaning, lambs drafted at 15 kg CW until 5 January when all remainder sold store, dryland farming. Data collected 1997 to 2000.

Cost of renewal $250/ha

Time of renewal
    Chicory, red clover: 5 years
    Tall fescue: 7 years
    Hybrid rye grass: 3 years
    Perennial ryegrass: 20 years

Farmlet Control: 12 Perennial Ryegrass paddocks Farmlet Improved: 5 Hybrid ryegrass + chicory, 3 tall fescue, 4 chicory + red clover.

Cost of renewal per hectare/year
Control $12
Improved $56

The revenue considered is only from additional lamb weight and assumes the same lambing percentages.

Lamb live weight gain
Lamb Income
Net Benefit
Birth to Weaning    Post-weaning

Net benefit to the improved system was $50-$60 per hectare. In addition, the ewes on the improved pastures are also about 6 kg heavier at mating and this should increase lambing percentages by about 12%; this is not included in the analysis. The ewes also produced an extra 0.4 kg of wool.

The above should be read in conjunction with other articles on this web site e.g.. Summer feeding of sheep (by Sue Mc Kay) and Pasture quality and alternative feeding of sheep (by Tom Frazer). For more extensive information, consult the Sheep council publication : A guide to improved lamb growth "400 plus"

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