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Sheep Research @ WMREC

Comparison of ram, wether, and short-scrotum lambs

The first small ruminants (goats) were grazed at the Western Maryland Research & Education Center in 2004. In 2005, lambs from a sire comparison study at the University of Maryland Eastern Shore were grazed at the facility. From 2006-2016, WMREC hosted the popular Western Maryland Pasture-Based Meat Goat Performance Test. In 2018, a new sheep research program was initiated. The first project was a comparison of ram, wether, and short-scrotum lambs. The project will be repeated in 2019, with a 4th treatment group (as yet, undecided),


A ram is an intact (entire) male sheep. A wether is a neutered male, whose testicles have been altered or removed. 65.5 percent of US sheep operations band ram lambs; banding is the most popular method of castration (87.5%). A short-scrotum lamb is a ram lamb whose empty scrotum has been banded, after his testicles have been pushed up inside his body cavity.

Research (and experience) has shown that ram lambs grow faster and produce leaner and more muscular carcasses than wether lambs, but ram lambs can caused unwanted pregnancies if they are housed or grazed with females.  The expectation is that short-scrotum rams will perform as well as intact males, but without the ability to impregnate females.  

The reason short-scrotum lambs should perform similarly as rams is because they still have a source of testosterone. Testosterone is produced by the testes. The short-scrotum lambs still have their testicles, albeit in their bellies. Testosterone is responsible for male traits, including superior growth and muscling and male behavior.

The short reason scrotum lambs should not be able to impregnate females is because they lack the thermoregulation of the intact males. The testicles must be several degrees cooler in order to produce sufficient viable sperm. However, the short-scrotum lambs should still demonstrate a desire to breed.

2018 Project

A private farm provided sixty (60) lambs for the 2018 study. Every third single, twin, and ram lamb was either left intact, castrated, or made a short-scrotum lamb. The short-scrotum lambs were made by pushing the testicles into the body cavity and banding the empty scrotum. The short-scrotum procedure and castrations were done by the time the lambs were 7 to 10 days of age. All lambs were docked and vaccinated for CDT (two injections). Lambs were early weaned, as part of a dairy sheep management program.

The lambs (rams, n=19; wethers, n=23; and short-scrotums, n=17) were delivered to the Western Maryland Research Center on April 26. Initially they were fed hay (mixed grass/alfalfa) because pastures were not yet ready for grazing, due to the cool, wet spring. Though the lambs were already accustomed to grain, they were initially fed a small amount of grain. The amount was gradually increased until they were consuming 2 lbs. per head per day. The grain was split into two equal feedings and was fen in 8-foot galvanized feeders. There was no refusal (waste). Eventually, the feed was increased to 2.5 lbs. and to 3 lbs. towards the very end of the project.

The lambs were maintained as a single group on pasture, grazing three separate pasture areas during their stay. Upon arrival, they grazed ~2.5 acres of mostly cool season grasses in a silvopasture area. After that, they grazed a five acre field of spring oats. Later in the summer, they grazed a 5 acre field of dwarf pearl millet. They were grazed (and fed) until August 14.

Despite the “moderate” level of nutrition, the lambs did not reach market readiness. Though they averaged 113.4 lbs. in body weight (just prior to slaughter) and yielded fairly muscular carcasses, most of the lambs had only 0.1 inches of back fat, as verified by ultrasound scanning and actual carcass measurements.

The lambs were handled bi-weekly to determine body weights and assess health status. No lambs required deworming or treatment for any disease condition.. A few lambs developed limps and developed ear tag (Shearwell EID) infections, but that was about all. They were a healthy bunch of lambs.

On August 6, the lambs were scanned to determine carcass characteristics (backfat and ribeye area/depth). On August 9, they were evaluated for fertility traits. Ending weights were determined (on certified scales) on August 14. The lambs were slaughtered on August 14 at Hamzah Slaughterhouse in Williamsport, Maryland. Hamzah is a Halal-certified plant. After the carcasses were evaluated the next day, they were broken down into primal cuts and transported to the University of Maryland campus, for use by the dining services.

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