Tuesday, August 21, 2018

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:
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

1 comment:

  1. Supposed the objective of this study was; to investigate the male fertility potential. Such as libido, in vitro and in vivo sperm traits (semen volume, sperm density, sperm mass pattern…).
    Indeed, many factors can affect the male animal's fertility. Such as breed, plasma testosterone, testis volume and weight, length of epidermis, animal weight, age, season, herd...
    In order to compare the effect of different levels of each factor on male fertility traits the other effective factors should be always considered. To do that a proper linear multiple regression model for significant factors should be designed. This statistical model is allowed the different factors to be compared accurately.
    Hope it will help you


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