1 Introduction</h5> In modern dairy herds, where reproductive management is on the basis of artificial insemination, the bull is considered a risk factor for fertility  . In that respect, the association between bull age and ejaculate characteristics has become highly relevant for the study of reproduction. Ejaculate volume and total sperm number increase with age and have been found to vary among bovine breeds [2–4] . On the other hand, advancing bull age is associated with a decrease in sperm motility and an increase in sperm defects  and sperm concentration  . In contrast, Hallap et al.  reported an increase in sperm motility and membrane integrity and a higher proportion of sperm with normal tail and acrosome morphology as bull age increases. Nevertheless, the mechanism underlying these alterations through aging is not clear.</P>Lipid and fatty acid composition is associated with semen physiological characteristics, which is considered as important reproductive predictor. For instance, Cerolini et al.  found that increased concentrations of free cholesterol, free fatty acids, triacylglycerol, and cholesterol ester are associated with decreased sperm motility and fertility. Similarly, in chickens, reduced male fertility was associated with low lipid content in the seminal fluid and
Theriogenology – Elsevier
Published: Oct 15, 2013
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