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https://doi.org/10.5713/ab.21.0271    [Accepted] Published online August 25, 2021.
Letrozole, an aromatase inhibitor, improves seminal parameters and hormonal profile in aged endangered Markhoz bucks
Ako Rezaei1,2  , Asaad Vaziry1,*  , Abbas Farshad1 
1Department of Animal Science, Faculty of Agriculture, University of Kurdistan, Sanandaj 661715175, Iran
2Department of Animal Science, Kurdistan Agricultural and Natural Resources Research and Education Center, AREEO, Sanandaj, 6616936311, Iran
Correspondence:  Asaad Vaziry, Tel: +98-8733664600, Fax: +98-8732246752, Email: a.vaziry@uok.ac.ir
Received: 12 June 2021   • Revised: 18 July 2021   • Accepted: 15 August 2021
Letrozole, a potent aromatase inhibitor, is known to have the potential to modify male reproductive function by altering sex hormone levels. This study aimed to evaluate the semen and testicular characteristics and hormonal profile of aged Mrakhoz bucks (Capra hircus) treated with letrozole.
Twelve Markhoz male goats, aged between 4.5 to 5.5 years with an average body weight (BW) of 61.05 ± 4.97 kg were used for the study. Animals were randomly divided into two equal groups and subcutaneously received either 0.25 mg/kg BW of letrozole or a control every week for 2 months. The semen collections were performed every 10 days, and blood samples and testicular biometric records were collected at 20 days intervals.
Letrozole causes increased testosterone and follicle-stimulating hormone levels, testosterone to estradiol ratio, semen index and reaction time during the period from 20th to 60th days (p<0.05). Furthermore, letrozole-treated bucks had higher semen volume, sperm concentration, and total sperm per ejaculate from 30th to 60th days (p<0.05). However, no differences occurred between the groups in scrotal circumference, relative testicular volume, semen pH, abnormality, acrosome integrity, and membrane integrity of sperm during the study (p>0.05). The serum luteinizing hormone levels, sperm viability, motility, and progressive motility increased, and estradiol levels decreased after 40th to 60th days of letrozole treatment (p<0.05).


Letrozole application to aged Markhoz bucks provokes reproductive hormonal axis which, in turn, induces enhancement of semen production and quality.
Keywords: Aged Bucks; Aromatase Inhibitors; Seminal Plasma; Sex Hormones; Testis
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