Four steps to reducing lamb mortality

Take-home message:

Creating structured management plans specific to their individual farm could help producers improve lamb survival rates to as much as 95%. Key areas to focus on include good nutrition throughout pregnancy, provision of good birthing sites, ensuring lambs are at the optimal birth-weight for the breed, and giving ewes time to develop a maternal bond.​

Lamb mortality has remained at about 15% over the past few decades, of which 50% will occur in the first 24 hours after birth[1].

However with farm specific management plans, research suggests it is possible to reduce lamb mortality to 5% or less.

According to scientists, the main principles around improving mortality are around the physiological, behaviour, nutritional and health requirements of the lamb and its mother pre-and post-lambing.

Risk factors for lamb mortality can be grouped into four categories: trauma at birth; a poor bond between ewe and lamb; disease development and uncommon factors such as predation.

The management system used will have a large effect on the types of risk factors that are more prevalent.

Outdoor lambing is more likely to see a greater prevalence of deaths related to hypothermia and starvation, whereas indoor lambing is more likely to experience higher rates of infectious disease spread.

This highlights that, although it is imperative to be aware of all risks for lambs in their first few days of life, producers should concentrate on targeting their management plan to their specific system.

Physiological

Small lambs find it harder to maintain their body temperature once they are born, making them more prone to hypothermia. Ensuring lambs are born with a good body weight and are able to raise their own body temperature is key to increasing survival rates.

As well as the immunological properties of colostrum, it is also essential that lambs ingest the high fat and energy content of colostrum to help increase heat production. Smaller lambs are less efficient at suckling and so are often unable to suckle the required amount of colostrum. This becomes even more of a problem in outdoor lambs who, due to lower environmental temperatures, will require a larger volume of colostrum compared to indoor housed lambs.

Behaviour

Ewe and lamb behaviour before and after lambing are important to understand to ensure that a strong maternal bond is made. Ewes seek sheltered areas before lambing, so producers should make sure there are plenty of areas to suit the flock size. If there are not enough lambing sites, ewes are more likely to lamb close together and there may be an issue over mis-mothering and contamination of sites.

Provision of shelters in advance of lambing will ensure that ewes are used to them and likely increase their use. It is also important to give the lamb and ewe plenty of time in the lambing area so they develop a bond ad learn to recognise each other.

Health

Lambs require a passive immunity from their mother through intake of good-quality colostrum in the first 24 hours after birth. As many as 22% of ewes on-farm are reported to produce colostrum that is inadequate for the lamb (<50 g/L immunoglobulin G). There are several ewe related factors which affect colostrum quality, but the main factor in control of the farmer is nutrition provision in late pregnancy.

Recent on-farm research has shown that it is better for lambs to suckle colostrum for themselves. Flocks that are tube fed have higher mortality rates, which may be attributed to infections transmitted through the tube.

Hygiene must be maintained throughout the lambing period to prevent the spread of infection, especially in indoor systems. New bedding should be provided daily in lambing pens during the initial neonatal period.

Nutrition

Under nutrition of outdoor ewes is common during pregnancy due to the lack of nutrient rich grazing during winter. Ewes that are underweight before mating are less likely to be able to cope with under-nutrition during pregnancy, as they have less fat reserves to draw on. Therefore regular body condition scoring around mating is important. KPI work at AHDB Beef and Lamb advises aiming for a body condition score at tupping of 2.5 for hill ewes; 3 for upland and 3.5 for lowland, this will also increase lamb weaning weights.

A further consideration is the effect of nutrition on the quality of colostrum produced. Metabolic profiling three weeks before lambing can be useful to investigate the nutritional state of your ewes. At three weeks, there is still enough time to tweak the nutrition to improve colostrum.

Key goals for improving lamb survival

•   Good ewe nutrition throughout pregnancy, especially in the final six weeks

•   Provision of good birthing sites - shelter helps to improve thermoregulation

•   Optimal birth weight for the breed. Too light = reduced vigour and ability to thermoregulate;

     too heavy = birthing problems

•   Development of a maternal bond - encourages a ewe accept the offspring and allows suckling of colostrum

For more details, see Farming Connect

Article reproduced with kind permission by Farming Connect, written by Dr Ruth Wonfor, IBERS, Aberystwyth University