Sheep Abortion / Improving Your Lambing Percentage
Lambing percentage is a crucial and true production figure. It is defined as the number of lambs sold or retained as a percentage of the total numbers of ewes put to the tup. Many factors can reduce the lambing percentage and these may be identified at various stages of the production cycle.
1. Poor Scanning Results
At scanning time the expected scanning percentage will vary from flock to flock. Low ground flocks may achieve 190% or more while hill flocks would target around 110%. The barren rate should be as low as possible. If this exceeds 2%, further investigation should take place, as infectious causes of infertility may be present. Poor scanning results may be due to:
Poor body condition – check body condition of 20% of the flock pre-tupping. Aim for condition score 3 – 3.5 in lowland/upland ewes, condition score 2.5 – 3 in hill ewes.
Sub fertile or infertile tups – tups should be assessed for fertility 2 – 3 months before mating. Check teeth, toes and testicles and contact a vet if you have any concerns. Semen testing of tups is also available through the practice.
Tup power – traditionally 1 tup to 40 ewes was considered appropriate, however increasingly athletic and more robust tups are capable of much more provided that they are all fit and fertile. The tup to ewe ratio must be appropriate to the breed and type/area of ground the tups are expected to cover when out with ewes.
Poor Nutrition – forage must be adequate both in quantity and quality. Copper, cobalt, selenium and iodine status can be checked as deficiencies in these trace elements may contribute to poor scanning results. Flushing ewes on better quality grazing for up to one month before tupping should increase ovulation rates and improve conception rates.
Lameness – the flock should be assessed for lameness prior to tupping time and lame animals treated. There should be less than 5% lame animals in the flock. Use of Footvax may be appropriate if there is a high incidence of footrot.
Parasites – routine dosing for fluke and worms is commonly carried out pre-tupping. If ewes are in poor condition at any time of year, faecal samples should be collected and tested for worm and liver fluke eggs.
Toxoplasmosis – can be a cause of high barren rates in unvaccinated flocks. 6 – 8 barren ewes can be blood sampled with lab fees subsidised via the Barren Ewe Scheme which runs till the end of March each year.
2. High levels of abortion
Infectious diseases such as enzootic abortion and toxoplasmosis can cause high barren rates and abortions. These two diseases alone are responsible for nearly three quarters of all abortions diagnosed at veterinary laboratories nationwide.
Investigation is warranted if greater than 2% of ewes abort or if more than 2 abortions occur daily for several consecutive days.
If abortions are identified, all aborted material (lambs & placenta) should be submitted to SAC Perth for analysis. These samples will be tested for Enzootic abortion, Toxoplasmosis, Campylobacter and Listeriosis. Blood testing of 6 – 8 aborted ewes should also be carried out. Blood samples for EAE can be tested using the Flock Check Scheme with subsidised lab fees which runs to the 31st July each year. Border Disease causes abortion and may also produce ‘hairy shaker’ lambs. This disease can also be investigated by blood sampling.
Many of the infectious causes of abortion in ewes are diseases that can be transmitted to humans. Good hygiene is always important at lambing time (wear disposable gloves, wash hands, disinfect equipment) but especially when abortions occur.
3. High lamb losses – more than 95% of expected lambs should be born alive.
a) At lambing time
Good management of nutrition is essential in the weeks before and during lambing and can be assessed by blood sampling 8 – 10 ewes one month pre-lambing. This testing looks at energy and protein status and allows corrections to be made before lambing begins. Inadequate or unbalanced nutrition can lead to twin lamb disease, and poor colostrum production (quality and/or quantity), which in turn will lead to lamb diseases such as watery mouth and joint ill. If nutrition is unbalanced or overly generous it is likely that problems will occur due to large lambs, difficult births, hung lambs, ewe prolapses etc.
b) At grass
Again good ewe nutrition is essential to ensure an adequate supply of milk to the young growing lamb. Ewes should also be checked for mastitis and treated promptly. The lambs themselves can be affected at this stage of life by Clostridial disease (such as pulpy kidney, lamb dysentery, braxy), Pasturella and parasites. Any lambs that die should be taken to SAC Perth for investigation. Vaccination or worm/coccidiosis control plans can be made as appropriate based on the results. Faecal samples taken from lambs throughout the summer grazing season can help to identify if and when worming is required.
In addition to calculating the lambing percentage, the percentage losses from scanning to sale can be assessed. Losses of greater than 15% should be investigated – contact the practice to discuss this and to improve your overall flock performance. Replacement rates in the ewes should not exceed 20% so again contact the practice to discuss your flock replacement policy.
Flock performance record cards are an ideal, easy to use way of assessing your flock performance and identifying areas for improvement. These cards are available in reception for you to collect along with a guide to abortion and vaccination (produced by MSD Animal Health). Please contact the practice to discuss your records or for assistance in reviewing your flock performance. We will be happy to help.