Survey of beef bulls in Brazil to assess their role as source of infectious agents related to cow infertility

Abstract

Poor reproductive performance in beef cattle caused by infectious agents results in major financial losses as a result of reduced pregnancy rates and extended calving intervals. Bulls can be subclinical chronic carriers of bacterial and protozoal agents involved in cow infertility, such as Campylobacter fetus subsp. venerealis, Ureaplasma diversum, Mycoplasma bovigenitalium, Mycoplasma bovis, and Tritrichomonas foetus. Bulls harbor these microorganisms in their preputial crypts and transmit the agents to cows during natural mating. To obtain an overview of the etiologic agents in the preputial mucus of bulls, we aimed to identify, by PCR assay, C. fetus subsp. venerealis, M. bovis, U. diversum, M. bovigenitalium, and T. foetus in Brazilian bulls from farms with high infertility rates. We collected preputial mucus from 210 bulls on 18 beef cattle farms in Brazil between 2019 and 2020. We found at least one of the infectious agents that we were studying in bulls on 16 of the 18 beef cattle farms tested. We detected at least one infectious agent from 159 of 210 (76%) bulls tested, namely C. fetus subsp. venerealis, M. bovis, U. diversum, M. bovigenitalium, and T. foetus in 87 (55%), 84 (53%), 45 (28%), 28 (18%), and 1 (0.6%) animal, respectively. We found 95 bulls (60%) positive for only 1 etiologic agent (single infection) and 64 bulls (40%) carried multiple agents. Our results demonstrate the occurrence of bacterial and protozoal infectious agents that may be related to infertility in Brazilian beef cattle herds.

What about the bull? A systematic review about the role of males in bovine infectious infertility within cattle herds

“…Mycoplasma spp. are already known to be associated with potential reproductive problems in bulls ( Parker et al., 2018 ), whereas M. bovigenitalium and M. bovis appear to be carried by breeding bulls ( Carli et al., 2022 ; Dudek et al., 2020 ). In females, infections by Mycoplasma spp.…”

“…In females, infections by Mycoplasma spp. translates onto reproductive disorders, such as vulvovaginitis, endometritis, dystocia ( Parker et al., 2018 ), earlier return to estrus, and sporadic abortion ( Carli et al., 2022 ), whereas the pathogenesis in bulls has been less studied ( Carli et al., 2022 ) and the absence of symptoms could be common ( Parker et al., 2018 ). Ureaplasma spp.…”

“…For example, Carli et al. showed the possible effect of coinfections on fertility, e.g., U. diversum and M. bovis present in 19.5% of bulls with low fertility rates ( Carli et al., 2022 ). However, coinfections and synergy between microorganisms could be more common than expected, as suggested by recent studies, which have characterized microbial populations by massive sequencing.…”

“…Males play an important role in infectious cattle infertility within the herd in two ways: directly (by which pathogens affect the reproductive potential of bulls or sperm quality ( Carli et al., 2022 ; Givens, 2018 )) or indirectly (by which microorganisms are transmitted from males to females through natural breeding and artificial insemination but are potentially asymptomatic for bulls ( Carli et al., 2022 ; Givens, 2018 ; Michi et al., 2016 )). Consequently, the impact of certain microorganisms potentially present in bulls on fertility must be considered to avoid problems such as delayed conception in females, which prolongs the calving season and increases the number of culled animals, resulting in a reduction in the efficiency of production and, consequently, economic losses ( Carli et al., 2022 ; Kastelic, 2013 ).…”

“…Males play an important role in infectious cattle infertility within the herd in two ways: directly (by which pathogens affect the reproductive potential of bulls or sperm quality ( Carli et al., 2022 ; Givens, 2018 )) or indirectly (by which microorganisms are transmitted from males to females through natural breeding and artificial insemination but are potentially asymptomatic for bulls ( Carli et al., 2022 ; Givens, 2018 ; Michi et al., 2016 )). Consequently, the impact of certain microorganisms potentially present in bulls on fertility must be considered to avoid problems such as delayed conception in females, which prolongs the calving season and increases the number of culled animals, resulting in a reduction in the efficiency of production and, consequently, economic losses ( Carli et al., 2022 ; Kastelic, 2013 ). Indeed, certain authors have suggested that low fertility in extensive herds is probably due to the fact that the importance of the bull has been overlooked, for example, in terms of the importance that infectious diseases, such as bovine diarrhea (caused by BVDV) and bovine rhinotracheitis (caused by BoHV-1), may play in the low fertility rates of female herds, in which these etiological agents could be transmitted from males ( Montoya-Monsalve et al., 2021 ).…”