Fertility: Preliminary Results

The fertility of ram (n=17), wether (n=24), and short-scrotum (n=17) lambs was evaluated. Blood samples were collected from each lamb to measure testosterone levels.

Libido was evaluated using a pen test. Each lamb (n=60) was placed in a 8 ft. x 8 ft. pen with two estrus ewes. The ewes had been treated with CIDR inserts so that they were in estrus (heat) on the day of testing (August 9). There were two pens of two ewes. Lambs were randomly assigned to a pen (A or B).

Each lamb was in the pen with ewes for five minutes. Breeding behaviors were observed and recorded. Behaviors observed included sniffing, butting, kicking, lip curling (flehman's response), mounting, servicing (ejaculating), and time to service.

Pen test to evaluate libido

The short-scrotum lambs displayed similar breeding behavior as the ram lambs, though the ram lambs had twice as many services and a shorter time to service (table 1). 

Table 1.  Libido

Sex	No.	Mounts, #	Services, #	Time, sec.
Ram	19	1.78a	1.11a	103a
Short scrotum	17	2.05a	0.53b	143a
Wether	24	0.22b	0c	NA

Numbers with different superscripts are statistically different.

Semen was collected from six rams and six short-scrotum lambs. An estrus ewe was used for collection. The semen was collected using an artificial vagina (AV). The semen samples were evaluated on site, then later in a lab by Dr. Dahlia O'Brien from Virginia State University.

Ejaculates of short scrotum lambs were essentially devoid of sperm and could not be tested with standard procedures.  Ejaculates of the intact rams had a concentration of 1.2 billion sperm/ml, 87% motility, and 82% viability. Ejaculate characteristics of short scrotum males would have rendered them sterile.

Click to view video of ejaculate from intact ram lamb
Click to view video of ejaculate from short-scrotum lamb

Testicles were collected at the time of slaughter, five pairs each from rams and short-scrotum lambs. The testes were dissected and weighed by Dr. Stephan Wildeus at Virginia State University. The short-scrotum lambs had significantly smaller testes than the ram lambs: 114.5 g vs. 393 g. The testicles from the short-scrotum rams also had a different consistency. The epididmymal weight was also smaller (21 vs. 50 g) in the short-scrotum lambs, as were the ratios of parenchyma: tunica and testis: epididmymis (table 2)

Table 2. Organ weights

Sex	No.	Total testes, g	Epididymal wt, g	Parenchyma: tunica	Testis: epididymis
Ram	5	393.4a	50.0a	14.9a	7.31a
Short scrotum	5	114.5b	21.0b	12.0b	5.39a

Numbers with different superscripts are statistically different.

Testicles from short-scrotum (L) and ram (R) lambs