The influence of zinc and heavy metals in feed and water on the quality of cryopreserved bull semen

Abstract

This study aimed to assess the influence of different concentrations of zinc (Zn), lead (Pb), mercury (Hg) and cadmium (Cd) found in the feed and water provided to bulls on the concentrations of these metals in cryopreserved bull semen, and to determine their influence onto semen quality parameters. Correlations between heavy metal concentrations in the semen and the quality parameters of semen as estimated by computer-assisted sperm analysis (CASA) and flow cytometry (FC) methods were determined. A total of 40 cryopreserved semen samples originating from bulls housed in 4 different centers for artificial insemination (A, B, C and D) were examined, making a total of 160 samples. The concentrations of metals and semen quality parameters were determined in cryopreserved semen of 10 bulls from each center, namely 4 samples from each bull. Concentrations of Zn, Pb, Hg and Cd in hay and concentrated feed were within the allowed limits as proposed by the National Research Council (NRC, 2000). A strong negative correlation was detected between curvilinear velocity (VCL) and Zn concentrations in the semen (P < 0.01; r = -0.772) in group D, and a positive correlation of VCL with Pb concentrations (P < 0.05 and r = 0.718) in group B. Mercury concentrations in cryopreserved semen correlated negatively to the percent of live sperm cells with intact acrosomes (V/IA: P < 0.05; r = -0.640) and positively with the percent of dead sperm cells with damaged acrosomes (D/DA: P < 0.01; r = 0.766) in group D. This finding confirms the hypothesis that Hg, even at low concentrations, may cause acrosome damage.

Cilj rada bio je da se ispita uticaj različitih koncentracija cinka (Zn), olova (Pb), žive (Hg) i kadmijuma (Cd) iz hrane i vode na koncentracije ovih metala u duboko zamrznutom semenu nakon otapanja i da se ispita njihov uticaj na parametre kvaliteta semena. Korelacije između koncentracije teških metala u semenu i parametra kvaliteta semena su određivane nakon ispitivanja semena kompjuterski asistiranom analizom semena (eng. computer-assisted sperm analysis - CASA) i protočnom citometrijom (eng. flow cytometry - FC). Iz 4 različita centra za veštačko osemenjavanje (A, B, C i D) ispitivano je po 40 uzoraka duboko zamrznutog semena bikova, što čini ukupno 160 uzoraka. Koncentracije metala i parametri kvaliteta semena su određivani u duboko zamrznutom semenu od 10 bikova iz svakog centra, odnosno 4 uzorka od svakog bika. Koncentracije Zn, Pb, Hg i Cd u senu i koncentrovanim hranivima bile su ispod propisanih dozvoljenih vrednosti Nacionalnog Istraživačkog Veća (eng. National Research Council - NRC, 2000). Jaka negativna korelacija uočena je između krivolinijske brzine spermatozoida (eng. curvilinear velocity - VCL) i koncentracije Zn u semenu (P < 0.01; r = -0.772) u grupi D, i pozitivna korelacija između VCL i koncentracije Pb (P < 0.05 and r = 0.718) u grupi B. Koncentracija žive u duboko zamrznutom semenu negativno je korelirala sa procentom živih spermatozoida sa neoštećenim akrozomom (eng. live sperm cells with intact acrosomes - V/IA: P < 0.05; r = -0.640) i pozitivno sa procentom mrtvih spermatozoida sa oštećenim akrozomom (eng. dead sperm cells with damaged acrosomes - D/DA: P < 0.01; r = 0.766) u grupi D. Ovi rezultati potvrđuju hipotezu da Hg, čak i u niskim koncenracijama može da prouzrokuje oštećenje akrozoma.