Abstract
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.
Highlights
We focused our attention on whether heavy metals might be present in mammalian seminal plasma, influencing important functions of sperm cells
The results of our study suggest that increased Pb concentrations in the cryopreserved semen increased the percentage of sperm cells showing curvilinear motility in group B, where the concentration of Zn was the lowest due to the competitive relationship with Pb
Exposure of breeding bulls to Hg from feed and drinking water, even in amounts below proposed limits, may exert detrimental effects on their reproductive health and especially on the integrity of the acrosome membrane. This is confirmed by the strong negative correlation and statistically significant difference between Hg concentration in semen and V/IA and positive correlation to damaged acrosomes (D/AD) values
Summary
We focused our attention on whether heavy metals might be present in mammalian seminal plasma, influencing important functions of sperm cells. The reproductive epithelium is a sensitive tissue that reacts to changes in concentrations of certain chemicals, as well to changes in environmental parameters. According to this criterion, all chemical elements can be divided into three groups. The second group are microelements, which are found in traces (Zn, Cu, Mn, Co and Se) Their presence in the ejaculate is necessary for the majority of spermatozoa functions, but increased concentrations might be toxic. The third group of elements are heavy metals (Pb, Cd, Hg and Ni) which, even in small concentrations in the ejaculate, lead to sperm cell damage [1]. Low levels of toxic elements, including aluminum (Al), arsenic (As), cadmium (Cd), lead (Pb), antimony (Sb), thallium (Tl) and uranium (U), have been demonstrated to exert detrimental effects on the reproductive health of rats [3,4]
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