New Zealand


The key factors that impact a lamb’s performance start with the ewe prior to the lamb being born. These factors are:


The minimum pasture cover for ewes carrying multiple lambs should be 1200kgDM/ha (3.5-4.0 cm pasture height) in late pregnancy, and this should increase to 1400kgDM/ha (4.5-5.0 cm) in early lactation. Hence lambing should be timed so that it coincides with an increase in pasture growth rates.

Body condition score (BCS) also plays a significant role in influencing performance over lambing, for example milk production increases as body condition score increases. As a result, we should be aiming to have the ewes at BCS 3 or better pre-lamb in order to maximise milk production.

One of the single most important factors influencing the profitability of the ewe flock is the percentage of ewes in the flock that are below BCS 3 at mating and lambing. There is nothing on a farm that will give a better return for the feed consumed, than taking a BCS 2 ewe and getting her to BCS 31.

Pre-lamb Early lactation
Minimum pasture cover 1200 kgDM/ha 1400 kgDM/ha
Minimum pasture height 3.5-4.0 cm 4.5-5.0 cm


Parasites will have an impact on both the ewes and their lambs. Ewes in late pregnancy, that are carrying multiple lambs, simply cannot eat enough pasture to meet their total energy requirements, as a result their immune system becomes compromised. This allows more infective larvae to survive and become established, and the existing parasites to increase their egg output.

The size and duration of this rise in egg output will often depend on the degree of stress the ewe is under. Generally, the greater the stress, the greater will be the period of higher egg output. The size of this contamination dictates the degree of exposure for the lambs once they start grazing pasture.

The periparturient rise in egg count of the ewe is often a good indicator of the stress the ewe is under.

Pre-lamb Parasites Challenge

In order to effectively reduce this exposure, we need to match the drench treatment of the ewes with the likely period of contamination. This is best achieved by dividing our ewes up based on the number of lambs they carry and their body condition score.

  • Poor conditioned ewes carrying multiple lambs need the longest cover, so a long acting product like Cydectin® Long Acting Injection for Sheep is an ideal choice.
  • Ewes carrying multiple lambs that are in good body condition, and ewes carrying single lambs but are in poor condition may need treatment if other factors such as poor feed level and early lambing dates put them under more stress. Where this occurs, a shorter period of parasite cover is probably appropriate. Eweguard® or Cydectin injection are ideal choices in this situation.
  • Ewes in good body condition that are only carrying a single lamb do not need any anthelmintic treatment.
Ewe Treatments

Trial work looking at treating poor conditioned ewes carrying twins with Cydectin Long Acting Injection for Sheep, showed that by weaning the treated ewes were 3.2kg heavier, and their lambs were 2.6kg heavier than those of untreated ewes2. It also showed that about 40% more of the treated ewes were at BCS 3 or better by weaning, meaning less feed was required to get them up to mating weight over the summer and autumn. This feed could then be allocated for lamb fattening.

BCS Ewes

Disease Management

To optimise not only lamb health but also the number of lambs for sale, lambs need to be protected from disease. Vaccination of the ewes pre-lamb with a clostridial vaccine such as Ultravac® 5in1 vaccine will ensure the ewes produce colostrum for their lambs which have high levels of protective antibodies. These antibodies should protect the lamb for 6-8 weeks.

Lambs need to be able to produce their own antibodies before this period of protection is finished. Hence lamb vaccination should begin at docking and repeated 4-6 weeks later or as close to this time as possible, at the next yarding.

Work has shown that about 13% of lambs do not receive adequate levels of maternal antibodies3. Yet another reason to ensure these lambs get vaccinated as soon as possible to prevent unnecessary losses.

Trace Elements

Supplementation of ewes or lambs with minerals or vitamins will only be of benefit if a deficiency exists. Where deficiencies of vitamin B12 and selenium do exist, supplementation of the ewes pre-lambing has been shown to be effective4.

Ewes can be treated with Ultravac 5in1 with selenium 2-4 weeks pre-lamb. This is for adult sheep only and not for use in lambs at docking.

Selenium supplementation is used to prevent white muscle disease. A condition that causes damage and scarring of the skeletal or heart muscle and can result in lambs being born dead or developing a stiff back and hind leg muscles, 3-6 weeks after birth. Subclinical ill-thrift can also be seen where the deficiency is less severe.

Vitamin B12 deficiency is seen where farms are cobalt deficient. Vitamin B12 is used by ruminants in the pathway for glucose production. Deficiency results in poor growth rates in lambs generally around weaning. Additional supplementation of lambs at docking and weaning with Ultravac 5+1 B12 or Ultravac 5+1 Se B12 is a cost-effective option.

In summary

To maximise the performance of our lambs we need to minimise the environmental factors that will negatively affect their health and production. This needs to start with the ewe. Plans must be set in place well before pre-lambing to ensure the BCS and feeding targets are met and that the requirements for supplementation, disease prevention and parasite control are adequately covered. Use the best products which match the differing unique requirements of ewes that may be carrying single or multiple lambs for optimal results.


  1. Beef and lamb NZ. Ewe body condition scoring handbook. May 2013
  2. Bingham, C., et al. (2017). "Comparison of two long acting pre-lambing anthelmintic treatments on the productivity of ewes in low body condition." New Zealand veterinary journal 65(3): 152-155.
  3. Sutherland, S. (2019). Colostrum intake by lambs on four commercial farms in the wairarapa. Proceedings of the Society of the sheep and beef cattle veterinarians and the deer branch of the NZVA, Wellington.
  4. Miller, C. M., et al. (2015). "Production benefits from pre- and post-lambing anthelmintic treatment of ewes on commercial farms in the southern North Island of New Zealand." N Z Vet J 63(4): 211-219.