SheepNet produces first technical datasheets
Prof. Cathy Dwyer, Dr Antonello Carta, Prof Fabien Corbiere
SRUC Scotland, Agris, Sardinia, INRA France
SheepNet is an EU funded project on sheep productivity and involves the 6 main EU sheep producing countries (United Kingdom, Spain, France, Ireland, Romania, and Italy) and Turkey. The three main topics on which SheepNet works are improving reproductive success, gestational efficiency and lamb survival. SheepNet have been produced 3 technical data sheets on improved reproductive and gestation efficiency, and improved lamb survival. These data sheets are translated into the 6 languages of SheepNet.
Fertility in sheep averages 90% but there is considerable flock and breed variation in fertility and number of lambs produced per ewe joined to the ram. However, low fertility is preventable and can be improved by tackling the main risk factors. Adequate nutrition of the ewe and ram, ensuring good environmental and health management and an appropriate number of ewes per ram are highlighted as the main route to improving reproductive success.
Embryonic loss and abortion will occur but this can be minimised by tackling the main causes and risk factors on farm. Appropriate nutrition before and during gestation are important to improve the survival of fertilised embryos, and ewe health is also critical. Abortion outbreaks of over 5% of ewes should always be investigated and can be reduced by maintaining good biosecurity and vaccinating ewes against the main infectious abortion agents.
Average lamb mortality before weaning is 15-25% but significant between flock variation (3%-50% mortality) exists. Highest mortality occurs on the day of birth, and nearly half of all deaths will occur in the first week of life. Lamb survival can be improved by attention to management and selection of appropriate breeding stock. Good ewe nutrition is critical in reducing lamb deaths. Provision of a suitable lambing environment, maintaining good hygiene and providing extra attention to vulnerable groups (larger litter sizes, inexperienced ewes) will also help to minimise losses.
SheepNet will hold its next transnational workshop in Sardinia in November 2018. Stakeholders who are interested in participating can register on line on the SheepNet website (http://www.sheepnet.network).
SheepNet is an EU funded project on sheep productivity and involves the 6 main EU sheep producing countries (United Kingdom, Spain, France, Ireland, Romania, and Italy) and Turkey. Ewe productivity (number of lambs reared per ewe joined), which has been static for the past few decades, is a combination of reproduction success (improving ewe fertility and ovulation rate), gestational success (maintenance and appropriate development of fertilised embryos and preventing abortions) and lamb survival. These three areas are the targets for the SheepNet project.
SheepNet has developed three technical datasheets which provide the frame of reference and the current state of knowledge for each of these areas. These have been translated into the 6 different languages of SheepNet and are freely available to download through the SheepNet website (http://www.sheepnet.network).
Improving reproductive efficiency
Reproduction efficiency of sheep is measured by fertility rate (the percentage of ewes lambing per ewe joined with rams or artificially inseminated [AI]) and prolificacy (the number of lambs born per ewe lambing). The economic relevance of the two parameters depends on the production system, i.e fertility is crucial in dairy systems where milk yield is the most important source of income, whereas prolificacy is more relevant in meat systems. The worldwide acceptable rate of fertility is around 90%, whereas prolificacy depends very much on the sheep breed, varying from 1 to 4 lambs per ewe lambing.
It is well known that, within a sheep breed, reproduction efficiency can vary widely, with fertility rates less than 70% and prolificacy as low as 1 lamb per ewe lambing. The improvement of these parameters is possible, with the best flocks reaching 95-100% fertility rate and litter size up to 3-4 lambs in prolific breeds. To optimize the reproductive efficiency of a flock it is fundamental to consider the management of the flock during the reproduction cycle, according to the genetic potential of the breed.
Reduced fertility rates may result from management factors affecting either male and/or female reproductive performances. Ewes may fail to become pregnant because they are not mated or because they are unable to conceive after mating or AI. In addition, ewes may not maintain the pregnancy or lose some or all of their fetuses during pregnancy (see later).
Ewes may not be mated because she is not in the right condition to breed (e.g. due to ill health, poor nutrition or age), is not cycling, or the ram is not able to serve the ewe (e.g. due to ill health, libido or too many ewes per ram). Ewes may not conceive because of poor egg or semen quality, stress (e.g. heat or handling), or pathology. Reasons for poor prolificacy include: 1) insufficient energy in the diet prior to and during joining thus ewes been in moderate to poor body condition score; 2) early death of embryos; 3) very young or very old animals; 4) insufficient dose of eCG if used in the synchronization program before AI.
Each farm or flock may have different risk factors and prevalence for different causes of low fertility. Identifying the main reasons for fertility failure and the more important risk factors are key in developing mitigation strategies. Recording fertility data and identifying when and why sheep do not lamb will help to improve reproduction efficiency.
Improving gestation efficiency
Gestation efficiency in sheep is defined by the proportion of ewes known to have conceived that give birth to viable lamb(s). Average fertilization rate is around 90-95%, however, not all embryos and fetuses will survive until delivery. Abortions (termination of a pregnancy after day 30) can occur at any stage of pregnancy.
Reduced embryonic and fetal survival rates may result from nutritional factors, infectious, fungal or toxic factors, maternal factors, environmental factors and genetic causes. These can affect the quality of the egg, and the physiology of the ewe, which increases the risk of embryo death. A range of bacterial, viral and parastitic agents, as well as plant-based toxins, can cause embryonic death and abortion. Caution must always be taken when handling aborted ewes and fetuses as some infectious microorganisms can be transmitted to humans.
Each farm or flock may have different risk factors and abortion at different gestational stages. Identifying the main reasons for abortion and the more important risk factors are the key steps in developing mitigation strategies. Recording whether ewes have bred (e.g. raddle marks), ultrasonography dates/results and abortion data, in order to identify when and why sheep do not lamb, will help to improve gestation efficiency.
Improving lamb survival
The average lamb mortality from birth until weaning or sale is between 15-25% worldwide, with a significant impact on financial margins. However, significant between-flock variation is known to exist, ranging from 3% to nearly 50% mortality. Lamb mortality is highest on the day of birth, and nearly half of all deaths occur within the first week of life, but the risk of dying remains higher for lambs than for adult sheep throughout early development.
The causes of lamb mortality have been well described across many different countries. Lambs die because of: 1) a difficult birth process (dystocia) causing hypoxia (lack of oxygen) or damage, 2) an inability to adjust to postnatal life, which can lead to starvation, mis-mothering and hypothermia, 3) infectious disease, 4) congenital malformation, 5) predation and 6) accident. The relative importance of these factors will depend on lamb age: for example newborn lambs are more likely to die because of birth difficulty (which can result in stillbirth, or may contribute to losses from other causes due to lamb damage), starvation and hypothermia, whereas older lambs may be more likely to die from infectious disease. The prevalence of different causes will also be affected by farm system. Indoor lambing systems can protect the lamb from hypothermia and predation, for example, but deaths from infectious causes may be more common. In outdoor systems, lambs may be more likely to die from starvation, hypothermia and predation, but will be less exposed to the build up of infectious agents.
The risk factors for lamb mortality are ewe undernutrition resulting in light lambs, poorer maternal care and less colostrum and milk; larger litter sizes and smaller lambs from multiple births are more vulnerable to starvation and exposure; maternal inexperience and genetic factors, stress or disturbance at lambing and the lambing environment.
Many of the causes of lamb mortality are preventable. A key goal should be for the lamb to suckle adequate amounts of colostrum from the ewe as soon as possible after birth. This will ensure a good bond between ewe and lamb, prevent starvation and hypothermia, and protect the lamb from some causes of infectious disease as gut closure will occur more quickly. Actions to improve lamb survival involve selecting animals with appropriate traits for the environment and the farm system, providing sufficient nutrition to ewes, particularly in late pregnancy, and ensuring a quiet and clean lambing environment.
SheepNet is open to all EU countries, stakeholders, sheep producers.