That Time of Year Again

Haley Zynda, OSU Extension Educator ANR, Wayne County

(Image Source: Michigan State University Extension)

As the days get shorter and the nights cooler, many shepherds are thinking about the upcoming breeding season. That is, if they haven’t already let their rams introduce themselves to the ladies. Breeding season is the exciting precursor and indicator of what kind of lamb crop you will have come spring. To ensure a successful lamb crop, there are a few things to consider and potentially remedy prior to letting the rams in with the ewes.

Just as bulls have breeding soundness exams (BSE), rams can go through a similar process to identify which rams should or should not be used. The Merck Veterinary Manual published a list of characteristics that need to be evaluated, the first of which is a semen analysis using an electroejaculator. Sperm are examined for morphology (physical appearance) motility. Total motility is the percent of sperm making any sort of movement, whereas progressive motility is the percent of sperm progressing forward in their movement. Progressive motility is the measurement you need to be most interested in, because if the sperm are only swimming in tight circles and not forward, chances of egg fertilization are quite low. Semen with 70% progressive motility or greater is considered exceptional and 30% – 70% is considered satisfactory. Greater than 50% of sperm need to be morphologically normal to be considered as satisfactory and greater than 80% for exceptional.

Other points of measure in the ram BSE are body condition, physical evaluation of the external genitalia and scrotum, and scrotal circumference. Rams should be a body condition score (BCS) of 3 – 4 going into breeding season. Breeding is strenuous, therefore thin rams may not have the energy and it may be too laborious for fat rams to perform their jobs. A physical examination should prove the ram clear of any irregularities in testes or epididymal masses. Lastly, scrotal circumference is directly related to sperm production. A breeding-age ram of 8 to 14 months should have a circumference of at least 28 centimeters; rams older than 14 months should be at least 32 centimeters.

Classifications for each point of measure include “exceptional,” “satisfactory,” “questionable,” or “unsatisfactory. Please note that a ram scoring a “questionable” or “unsatisfactory” rating in any category is automatically rated as that score overall. A ram can be “exceptional” if he scores such a rating regarding sperm motility and morphology and scrotal circumference.

Ewes do not have the same rigorous testing that rams have, but one similarity is that they also need to be of good body condition. A BCS score of 3 is ideal heading into breeding season and will improve their likelihood of producing twins. Thin ewes may only produce singles or not breed at all, and fat ewes may have issues at lambing with difficult births. Assessing BCS prior to adding rams to the mix allows you to flush the ewes with the proper amount of nutrition instead of over- or underfeeding. Ewes can be fed one half to a full pound of grain per day or offered high quality hay or grass pasture. Notice how it says “grass.” Legume pastures are rich in phytoestrogens or estrogens found in plants. By adding a reproductive hormone similar in structure but incorrect to the species, ewe cyclicity and conceiving ability can be impaired.

Vaccinating ewes against abortion-causing diseases should also occur before rams are introduced. Chlamydia and vibriosis are two such diseases that can be prevented with vaccines. You can find them in combination or individually and ewes should be inoculated 30 days prior to breeding.

One Big Happy Family
Once the ram(s) are in with the ewes, watching for breeding is important. Making sure the rams are sniffing out the females and trying to mount is a good indication of ram libido. If you can’t always have eyes on the flock, using a marking harness can help you visualize where the ram has been and how the ewes are cycling.

A ewe’s cycle is 17 days, therefore changing marker colors, every 17 days can also help you see which ewes are catching on the first cycle and which aren’t. If only a couple ewes are remarking, chances are the ewe is not reproductively sound. If a majority of the ewes are remarking with multiple colors, chances are the issue is stemming from the ram.

Remember that weather and decreasing daylight is the trigger for ewes to start cycling and there are breeds that more readily end their anovulation and start cycling. Fine wool breeds will likely start cycling before some of the medium and coarse wool breeds (think Suffolk, Border Leicester, etc.) Also remember that ewe lambs and mature ewes will come into estrus differently. Ewe lambs will have a shorter estrous period than their mature counterparts and the estrus will be less intense.

In summary, prepare yourself and your flock for breeding season before it is too late. Just a few small examinations and nutritional adjustments will likely make the 2022 lamb crop more profitable and that much more exciting.