Renowned Veterinary Specialist Practitioner, Dr Johan van Rooyen, provides insights into how farmers can improve the nutrition of their pregnant ewes.
The management of pregnant ewes can be divided into 4 phases: First, second and third trimester and lactation. Nutritional requirements in these four phases differ vastly and the metabolic demand is higher in each phase.
If you manage your ewes without supplements at least provide access to a phosphate lick at all times.
One of the most important management tools is the weighing of a sample group of ewes in each flock. Mark at least ten ewes in each group with a red paint mark on the head or a red ear tag and weigh these ewes every week or two. Ewes should be weighed roughly at the same time of day to avoid normal daily weight changes which could be as much as 5kg as a result of feed and water intake.
After weighing, calculate the average and record it in a graph. In this way you can monitor the effect of nutrition and supplements and adjust of necessary. Surprising results may be seen. The weights of the ewes often start decreasing even though the grazing may still seem to be adequate.
Parasites may be the cause but many times dirty water, phosphate or magnesium deficiency in the summer and protein deficiency in the winter can cause the problem. Corrections can be made long before the condition of the ewes become noticeable.
Wool ewes need to lose 15% of their body mass before it becomes obvious if their wool is long. Performing body condition scoring in a marked group of ewes can also be a useful management tool but it is more subjective and may not give good results.
Increasing the nutritional level before mating will increase conception rate but the level of nutrition must be maintained thereafter to prevent early resorption of the foetuses. The foetus only implants after three weeks and can die if nutritional levels decrease too much after mating. A serious Vitamin A deficiency may also cause early abortions.
Administering Selenium can cause the loss of foetuses under 35 days old. Blowfly strikes and wireworm infestation can have a very negative effect on ewe in this phase. If ewes are stressed after mating it will be found that the percentage twin ewes are normal but there may be unusually high number of dry ewes.
It is best to avoid shearing ewes in the first trimester. A high percentage dry ewe found after artificial insemination is often blamed on the catchup rams. It may however be that the ewes were in early pregnancy while the catchup rams were with them but they resorbed or aborted after mating as a result of stress. (Dog atacks, lack of water, poor nutrition, severe weather, parasites).
In the next article, the focus will be what do in the middle trimester pregnancy.
By Dr Johan A. van Rooyen M.Med. Vet. Specialist Veterinarian
Steynsburg Animal Hospital