The Ideal Lambing Season

By Mike Neary
Extension Sheep Specialist
Purdue University

The following scenario would approach the ideal lambing season:
  • All ewes bred
  • All mature ewesweaning twins
  • No lambing problems
  • No weak lambs
  • All ewes producing adequate milk
  • All ewes good mothers
  • No bummer lambs
  • No health problems with ewes or lambs
  • 35 day lambing season
  • No predator problems
  • Good weather

One can't control the weather, but all other factors can be controlled with varying rates of success. Certainly, type and size of sheep operation will modify what is considered an ideal lambing season. Envirornnent will dictate number of lambs weaned per ewe. Realistically, an ideal lambing season is not likely, however, we can manage the ewes to approach the ideal as close as possible.

Hopefully pre-breeding management has been sound, i.e. flushing ewes, culling of ewes, breeding soundness exam on rams, appropriate health program for ewes and rains, etc. Much of the success or failure of a lambing season begins with the breeding season. However, the primary focus of this article will be from breeding to parturition.

Early Gestation

The period of early gestation most critical to success during the lambing season is the first 30 days after fertilization. The first 21 to 30 days after breeding is when embryonic implantation occurs. This first 30 days is when most embryonic mortality occurs. Thus, anything that can be done to reduce embryonic mortality and should result in more lambs bom. Shearing, vaccinating, working ewes, pronounced changes in feeding practices should be avoided during the first 30 days of gestation.

Ultrasonic pregnancy scanning can be done on ewes from 35 to 60 days after breeding, depending on equipment used and operator skill. Some operators can determine whether pregnant or not with 98 to 99% accuracy. Also, skilled operators can count fetal numbers with accuracy above 90%. With medium to large sized flocks, ultrasonic pregnancy scanning will save producers money and the information obtained can make management more efficient. Assume a I 00 head ewe flock with 95% conception. Identifying 5 open ewes with a weight of 160 pounds at $30/cut gives a return of $240. Also, assuming a hay saving of 650 lbs/ewe at $80/ton saves a producer $130. If it costs $2/ewe to pregnancy test ($200 total) the net positive cash flow would be $170. This would be independent of concentrate costs, vaccination costs, equipment use and needs and other management considerations. For a producer with a small flock the economic benefit may not be so clear, yet, the information generated may make management easier.

The "ideal lambing season scenario" identifies the goals of no lambing problems, all ewes producing adequate milk, no bum lambs and all ewes as good mothers. Some may consider these factors as being out of control of the shepherd. Yet, ease of lambing, milking ability and mothering ability are all heritable traits. Selection pressure for matemal traits is one of the most important tasks one can do to decrease labor and management inputs at lambing. If culling has not occurred prior to breeding, unsound ewes (cudders, feet, physical condition, age) and those having a history of problems should be culled during early gestation. Cull your problems. The long term fitness of the flock will increase. Labor and management inputs will decrease.

Nutrition during early gestation is quite simple. Ewes need only slightly above maintenance levels of nutrition for the first 15 weeks of pregnancy. Pasture, crop residue, average quality hay will meet the ewes nutritional requirements during this period. Certainly, a good sheep mineral should be available, with an adequate supply of water.

Late Gestation

The last 4 to 6 weeks of pregnancy is considered late gestation for the ewe. This is the period where proper management becomes critical in realizing an ideal lambing season. Ewe milking ability, lamb size and vigor at birth, ewe body condition, health problem prevention are all heavily influenced during this phase of gestation. Proper nutrition during late gestation is a must to have a successful lambing season.

Nutrient needs depend upon number of lambs a ewe is carrying. Flocks with average lambing rates of 180 to 200% need more nutrient inputs than those with a 120% lambing rate. Energy, water, vitamins and minerals are especially crucial as lambing approaches. Ewes carrying multiple births need a concentrated form of energy, such as corn, since the developing feti reduce the ewes rumen capacity. Selenium supplementation to ewes during late gestation is critical to prevent weak lambs, retained afterbirth and white muscle disease in lambs. Calcium and phosphorous requirements of ewes in late gestation essentially double as compared to the maintenance phase. Free choice availability of a good sheep mineral is important prior to lambing.

There should be several areas available prior to lambing to group ewes based on expected date of lambing. This prevents over or underfeeding ewes and makes timely management techniques easier to perform.

Ewes should be treated for internal parasites 2 to 4 weeks before lambing. Worming at this time is extremely effective at controlling a future parasite problem. There is a marked rise in fecal egg counts in ewes just before lambing. If a product is used that is effective against the hypobiotic stages of internal parasites, parasite control in ewes and lambs is enhanced. Ewes serve as the main source of infection for both lambs and the pasture.

Ewes can be vaccinated for tetanus and enterotoxemia (overeating) from 2 to 4 weeks before lambing. Antibodies received by lambs through colostrum will give them immunity for 5 to 6 weeks.

For producers that are shed or bam lambing, the ewes should be in short fleece prior to lambing. This results in increased lamb survival and decreased health problems. Ewes in full fleece take more room in a facility, are more apt to lay on lambs, bring more moisture into the facility and are more difficult to observe and manage. If shearing ewes in cold weather, be aware that they will need extra energy intake for a few days after shearing until their body metabolism adapts to the removal of wool.

Ventilation and sanitation of facilities are critical concerns for producers lambing inside during the cold months. Inadequate ventilation is the cause of moisture and ammonia buildup, which in turn leads to pneumonia and scours problems. Keeping facilities clean and well ventilated will prevent many health problems.

Feed additives can be fed to ewes during late gestation to prevent health problems and increase productivity. For instance, an antibiotic such as overomycin can be fed to ewes to increase lamb survival and decrease disease problems in ewes. Also, if an abortion problem exists, high levels of antibiotics can be fed to control outbreaks. Feeding ionophores (monensin, lasalocid) to ewes during late gestation can decrease future coccidia problems in lambs. Research at Purdue has shown that feeding lasalocid (Bovatec) during late gestation increased lamb vigor at birth and birthweight.

Give ewes ample opportunity for exercise. It increases ewe fitness, decreases the number of over fat ewes and makes for an easier lambing for the ewe and shepherd.

Organization Needs

Being organized makes the goal of an ideal lambing season more attainable. Make a list of equipment and supplies that might possibly be needed and then make them readily accessible. Some supplies should include; thermometer, stomach tube, iodine, supplies for dealing with difficult births, syringes, needles, commonly used medications, etc. The list could go on for infinity. The point being, be prepared. Expect the best, be prepared for the worst.

Devise an efficient record keeping system for use during lambing. Be sure to make notes on problems with individual ewes or lambs. Culling these problems will help make future lambing seasons more ideal.

Summary

Ideal lambing seasons don't happen by chance or luck. You make your own luck by proper management and preparation. Pregnancy testing, ruthless culling, proper nutrition, reproductive management, a sound health program and organization are all required for a successful lambing season. Ideally, working smarter should replace working harder.