Balanitis in beef herds in southern Australia

Summary

Veterinarians and beef producers in north-east Victoria and southern New South Wales have observed lesions on the penis (‘balanitis’) of beef breed bulls early in the mating period. This often leads to a reluctance of bulls to mate with cows (‘bull breakdown’), hence poor conception rates. The penile lesions had an inconsistent appearance not always typical of known viral causes of balanitis in cattle in Australia, namely Bovine Herpersvirus-1 and -5 (BHV-1 and -5). Additionally, veterinarians from different regions described the lesions and the effect on bulls differently.

There are two types of BHV that can cause venereal diseases in cattle, BHV-1 and -5. Clinical signs include reddening of the preputial or vaginal mucosae, pain associated with pustules or ulcerative lesions and abortion.  In bulls, the pain caused by the lesions can lead to reduced serving capacity, hence reduced conception rates in the cow herd. 

The initial studies identified that BHV-1 was associated with balanitis in some bulls, however not all the bulls with clinical signs were positive for BHV-1. Therefore, the primary aim of this project was to identify the cause of mid-season bull breakdowns caused by this syndrome, and establish if cows play any role in the transmission.

There were two parts to this project. Firstly, a producer survey to determine which farms may or may not have bulls affected with balanitis, followed by a serological survey to determine the prevalence of BHV in Victoria and southern New South Wales. Secondly, we attempted to identify farms which had a history of problems with bull breakdowns due to the syndrome described by veterinarians, serial sample a mob of cattle, bulls and cows and describe the progression of the syndrome, and risk factors associated with it, on these farms.

Samples were collected from four farms, two were located near Coolac in southern New South Wales, and the other two located at Ournie, just across the Murray River from Walwa in north east Victoria. Five visits occurred; before joining, at the start of joining, mid-joining, the end of joining and at pregnancy testing although, not all these visits occurred on all farms. All cattle had swabs taken of either their penile or vaginal mucosae, were visually assessed for lesion scores on this mucosa, had blood taken from their tail vein and a small number of bulls had biopsies taken of the lesions on their penile mucosae.

Swabs were used for a PCR that identified the presence of BHV-1 and -5 and a universal PCR was used to identify the presence of BHV. Samples which were negative for BHV-1 or -5, but positive on the universal PCR were assumed to be BHV-6 after sequencing of a proportion revealed this. The bloods were sent to IDEXX laboratories for immunoserological testing using an ELISA which detected glycoprotein-B-specific antibodies to Bovine Herpesvirus 1.

Results from the serological survey showed a wide range of sero-prevalence within herds tested, from 5.8 to 97.8%. There was a significant difference in the sero-prevalence of BHV in affected/suspected herds and non-affected herds, the overall average was 51.8% (range 5.8 to 97.8%) and 35.0% (range 5.8 to 84.0%), respectively (P<0.0001).>

The second part of the project identified the presence of BHV-6 in penile and vaginal swabs. The significance of this finding is yet to be determined. Bovine Herpesvirus-1 and -5 were not identified in any of the samples collected, even though on two of the farms, the producers commented that the lesions present were typical of the syndrome.  

Bull breakdowns can be devastating for beef enterprises, because no calf equates to no income. This project highlights the need for producers to get bulls examined by veterinarians, especially if there is no obvious reason for their breakdown. The financial benefit to producers is avoiding a disaster, either through poor conception rates or the need for an extended mating period due to a change of bulls halfway through the joining period. An extended mating period also creates problems with late-born steers not reaching turn off weight, and late-born heifers failing to reach mating weight.</0.0001).>

The financial benefit to producers is avoiding a disaster, either through poor conception rates or the need for an extended mating period due to a change of bulls halfway through the joining period. An extended mating period also creates problems with late-born steers not reaching turn off weight, and late-born heifers failing to reach mating weight.

Objectives

The aim of this project was to identify the cause of mid-season bull breakdowns in bulls with observed lesions on the penis and establish if cows play a role in transmission.

Key findings

The involvement of BHV-1 and -5, which were originally proposed as potential causal agents of this syndrome, was ruled out (at least in the material collected from the 4 suspect herds studied). However, the role of BHV-6 needs to be more fully defined by additional research and clinical investigations as outlined above.

It is highly recommended that beef producers should monitor mobs more closely during mating. If they suspect a problem with bulls failing to work, they should immediately respond by removing bulls and having the problem investigated by a competent veterinarian skilled in beef reproduction. This is particularly important in mobs of cows that are single-sire mated.

In addition, whilst not a direct finding from this project, a pre-joining examination of bulls is an initial and critically important step in addressing sub-optimal reproductive performance in a beef herd. This should include an overall examination (health and locomotion, mating/joining competence), plus a physical examination of the penis and testicles, to determine if the bulls are fit for service.

Benefits to industry

Bull breakdowns can be devastating for beef enterprises because no calf equates to no income. This project highlights the need for producers to have bulls examined by veterinarians, especially if there is no obvious reason for their breakdown.

The financial benefit to producers is avoiding a disaster, either through poor conception rates or the need for an extended mating period due to a change of bulls halfway through the joining period. An extended mating period also creates problems with late-born steers not reaching turn off weight, and late-born heifers failing to reach mating weight.

Future research

This project has raised many questions around bull management and the cause of balanitis in beef herds. Further research and development is required to answer these questions, for example investigating reproductive failure of bulls in beef herds across south-east Australia more broadly, examination of bulls when an outbreak occurs particularly in herds with a history of the syndrome, and development of best practice protocols for bull management.

Additionally, the role of BHV-6 needs to be more fully defined by additional research and clinical investigations.