Mycoplasma species in vaginas of dairy cows before and after exposure to bulls and their association with conception.

Mycoplasma species can colonize the urogenital tract of dairy cattle. However, interrelationships between Mycoplasma spp. and reproductive performance in dairy herds are unclear. In this study, we measured apparent prevalences of Mycoplasma spp. in the vaginas of dairy cows (n = 629) pre- and post-bull exposure in dairy herds with and without Mycoplasma bovis clinical disease (n = 5 herds), and assessed associations between variables describing reproductive performance and consequent Mycoplasma spp. isolation. Mycoplasma spp. were infrequently isolated from the vagina pre- (1.9%; 12/629) and post-bull (3.2%; 20/629) exposure. Of the mycoplasmas isolated, Mycoplasma bovigenitalium was isolated most frequently (87.5%; 28/32), followed by Mycoplasma californicum (9.3%; 3/32). Mycoplasma bovis was only isolated from one cow. We were unable to provide any evidence of venereal transmission of M. bovis in cows in M. bovis-infected herds that use natural service bulls. There was an insufficient number of cows with Mycoplasma spp. in the vagina pre-bull exposure to assess effects on subsequent reproductive performance. Cows that had not conceived before post-bull exposure sampling had much greater odds (odds ratio 14.8; 95% confidence interval 4.2 to 52.3) of having a Mycoplasma sp. isolated from the vagina at this time compared with those that had conceived. Also, within those that had conceived, delayed conception increased the odds of having a Mycoplasma spp. isolated from the vagina at the post-bull exposure sampling by a factor of 1.62 for every additional week not pregnant. The likely cause of these findings is that cows that remain not pregnant for longer are more likely to be served by a bull (likely repeatedly) and subsequently become colonized with a Mycoplasma sp. (mostly M. bovigenitalium) through venereal transmission. In dairy herds that use bulls, there is a greater chance of isolating a Mycoplasma sp. (mostly M. bovigenitalium) after a period of bull breedings from the vaginas of cows that have remained nonpregnant for longer during the bull breeding period.

Mycoplasma bovis and other Mollicutes in replacement dairy heifers from Mycoplasma bovis-infected and uninfected herds: A 2-year longitudinal study.

Replacement dairy heifers exposed to Mycoplasma bovis as calves may be at risk of future clinical disease and pathogen transmission, both within and between herds; however, little information is available about these risks. We conducted a 2-yr longitudinal (panel) study starting with 450 heifer calves reared to weaning in 8 herds (7 M. bovis infected with clinical disease, 1 uninfected) under the same ownership. After weaning, heifers were commingled and managed with non-study heifers at a single heifer rearing facility. Nose, conjunctival, and vaginal swabs were collected along with a blood sample at weaning, prebreeding, precalving, and approximately 1 mo postcalving. Additionally, a colostrum sample was collected upon calving and a composite milk sample was collected 1 mo postcalving. The swabs, colostrum, and milk samples were cultured for Mycoplasma spp., and serum from the blood was evaluated for serological evidence of exposure to M. bovis using an ELISA. Despite a high M. bovis ELISA seroprevalence at weaning in the heifers from the 7 M. bovis-infected herds with clinical disease [72% (289/400); range by herd: 28-98%], M. bovis was isolated from only 4% (16/400) of the same heifers at the same time. In heifers from the uninfected herd at weaning, M. bovis seroprevalence was 2% (1/50) and M. bovis was not detected by culture. Mycoplasma bovis was isolated from 0.5% (2/414) of heifers at prebreeding, 0% (0/374) of heifers at precalving, and 0.3% (1/356) of heifers 1 mo postcalving. The nose was the predominant anatomical site of M. bovis colonization (74%; 14/19 culture positives). A single heifer (from an M. bovis-infected herd with clinical disease) was repeatedly detected with M. bovis in its nose at weaning, prebreeding, and postcalving samplings. This demonstrates the possibility, albeit rare, of a long-term M. bovis carrier state in replacement heifers exposed to M. bovis as calves, up to at least 1 mo after entry into the milking herd. No M. bovis clinical disease was detected in any heifer from weaning through to the end of the study (approximately 1 mo after calving). Acholeplasma spp. were commonly isolated throughout the study. Mycoplasma bovigenitalium, Mycoplasma bovoculi, and Mycoplasma bovirhinis were isolated infrequently. Mycoplasma bovis seroprevalences at prebreeding, precalving, and postcalving samplings were 27% (112/414), 12% (46/374), and 18% (65/356), respectively. Overall, the results show that replacement heifers from groups exposed to M. bovis preweaning can become colonized with M. bovis and that colonization can, uncommonly, be present after their first calving. For groups of 50 or more heifers exposed to M. bovis preweaning, there is at least a nontrivial probability that the group will contain at least 1 shedding heifer postcalving.

Scrotal circumference, bodyweight and semen characteristics in growing dairy-breed natural-service bulls in Tasmania, Australia.

AIMS: To provide herd managers with a set of decision rules allowing them to predict the likelihood that a juvenile bull is ready for Bull Breeding Soundness Evaluation (BBSE), or breeding, if bodyweight and scrotal circumference are known. METHODS: This was a longitudinal study following two groups of young pasture-fed Holstein and Jersey bulls from northwest Tasmania, Australia. Individual scrotal circumference, bodyweight and semen characteristics were recorded at 6-8 weekly intervals, from 6-18 months of age. Classification and regression tree analyses were used to predict the probability that a bull had ≥70% normal sperm morphology based on scrotal circumference and bodyweight measurements. RESULTS: Overall 1,661 scrotal circumference and bodyweight measurements were obtained, and 518 semen samples from 356 bulls were assessed for sperm morphology, from 16 examination sessions that took place between 29 May 2015 and 17 August 2016. Classification and regression tree analyses generated a decision tree for Holstein bulls with four node endpoints, and for Jersey bulls with three node endpoints. Diagnostic test performance showed that for Holstein bulls, using the node endpoints of scrotal circumference ≥27 cm and bodyweight ≥349 kg, 98% had ≥70% normal sperm (positive likelihood ratio 10.4; 95% CI = 2.7-41), and using the node endpoints of scrotal circumference ≥27 cm and bodyweight between 282-349 kg, 89% had ≥70% normal sperm (positive likelihood ratio 1.6; 95% CI = 0.9-2.6). For Jersey bulls, using the node endpoints of bodyweight ≥259 kg and scrotal circumference ≥29 cm, 88% had ≥70% normal sperm (positive likelihood ratio 3.4; 95% CI = 1.6-7.0). CONCLUSIONS: This study provides a set of relatively simple decision rules based on bodyweight and scrotal circumference measurements that allows herd managers to assess the likelihood that juvenile bulls are ready for BBSE or breeding. ABBREVIATIONS: BBSE: Bull breeding soundness evaluation; BRT: Boosted regression tree.

Isolation of Mycoplasma spp. and serological responses in bulls prior to and following their introduction into Mycoplasma bovis-infected dairy herds.

With the common use of bulls for breeding following a period of artificial insemination in seasonally bred dairy herds, it is important to consider the potential role of the bull in transmission of Mycoplasma spp. within and between herds. This study aimed to assess the prevalence of Mycoplasma spp. in a population of bulls before and after use in Mycoplasma bovis-infected herds. The frequency of subclinical infection was also measured serologically postbreeding, and the association of Mycoplasma spp. on semen quality was evaluated. Mycoplasma bovis was isolated from 4 of 118 bulls after use in 4 herds infected with M. bovis. In the bulls, M. bovis seroprevalence increased from 9% prebreeding to 46% postbreeding with a total seroconversion rate of 44% across the 4 herds, with no evidence of clinical disease. There was no association of Mycoplasma spp. in the bulls' semen and abnormal palpation characteristics (enlarged or nodular) of seminal vesicular glands or poor semen quality attributes such as semen mass activity, sperm motility, and morphology. These results demonstrate a high degree of subclinical exposure of the bulls to M. bovis in infected herds and highlight the potential for bulls to be mycoplasma carriers within and between herds. Herd biosecurity protocols and control programs should take into account the potential role of bulls in the introduction and spread of Mycoplasma spp.

Short communication: Shedding of Mycoplasma bovis and antibody responses in cows recently diagnosed with clinical infection.

Mycoplasma bovis can have significant consequences when introduced into immunologically naïve dairy herds. Subclinically infected carrier animals are the most common way that M. bovis is introduced into herds. Although M. bovis udder infections can be detected by milk sampling lactating animals before their introduction, currently, no definitive way of identifying M. bovis carrier animals that are nonlactating (i.e., calves, heifers, dry cows, or bulls) is available. Understanding the prevalence of M. bovis shedding from various body sites in clinically infected animals could inform strategies for the detection of subclinical infection in nonlactating stock. The mucosal surfaces of the nose, eye, and vagina of 16 cows with recent clinical mastitis caused by M. bovis were examined for the presence of M. bovis shedding. Blood was collected for serological evaluation by a commercially available ELISA. Mycoplasma bovis was isolated from the vagina of only 3 (18.8%) of the cows and was not detected from the noses or eyes of any of the cows. Fifteen of the 16 (93.8%) cows were seropositive to the ELISA. With such low prevalence of detection of M. bovis from the vagina and no detections from the noses or eyes of recently clinically infected animals, it is very likely that sampling these sites would be ineffective for detecting subclinical infection in cattle. Serology using the ELISA may have some use when screening animals for biosecurity risk assessment. However, more information regarding time to seroconversion, antibody longevity, and test diagnostic sensitivity and specificity are required to define the appropriate use of this ELISA for biosecurity purposes.

Dicoumarol toxicity in neonatal calves associated with the feeding of sweet vernal (Anthoxanthum odoratum) hay.

Neonatal calves from a seasonal dairy herd in North Western Tasmania were presented for veterinary care due to mortalities and bleeding from multiple orifices. Necropsy examination revealed free blood throughout the parenchymatous organs, body cavities and connective tissues. There was no history of anticoagulant exposure, however, high quantities of dicoumarol were found in samples from hay fed to recently calved cows. No Australian cases of dicoumarol toxicity in neonatal calves have been previously documented, and dicoumarol toxicity in adult cattle would appear to be less common than in colder farming regions of the Northern Hemisphere.

An isoform-specific inhibitory domain regulates the LHX3 LIM homeodomain factor holoprotein and the production of a functional alternate translation form.

The LHX3 LIM homeodomain transcription factor is required for pituitary development and motor neuron specification. The Lhx3 gene encodes two isoforms, LHX3a and LHX3b, that differ in their amino-terminal sequences. Humans and mice with defective Lhx3 genes are deficient in gonadotrope, lactotrope, somatotrope, and thyrotrope pituitary cells. We show that, whereas Lhx3b is highly expressed in these Lhx3-dependent cell types, high levels of Lhx3a expression are restricted to alpha glycoprotein subunit-expressing thyrotropes and gonadotropes. Cross-species comparison reveals the LHX3b-specific domain is more conserved than the LHX3a-specific domain. We demonstrate that the LHX3b-specific domain is a transferable inhibitor that reduces gene activation and DNA binding by homeodomain proteins. In addition, we identify a novel LHX3 protein (M2-LHX3) and determine that this molecule is generated by an internal translation initiation codon. The LHX3a- and LHX3b-specific coding sequences regulate differential usage of this internal start codon. Further, we identify the major activation domain of LHX3 in the carboxyl terminus of the molecule. M2-LHX3 is active because it retains this domain and binds DNA better than LHX3a or LHX3b. Other LIM homeodomain genes, including Lhx4, generate similar truncated proteins. These studies describe how transcriptional regulatory genes can generate multiple functional proteins.