ORCID Profile
0000-0002-4586-4983
Current Organisation
University of Queensland - Gatton Campus
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Publisher: American Dairy Science Association
Date: 09-2023
Publisher: Frontiers Media SA
Date: 04-11-2021
DOI: 10.3389/FVETS.2021.743725
Abstract: Mastitis is the most common disease in dairy cattle worldwide. The objectives of this study were to estimate the prevalence of different bacterial species associated with mastitis from dairy herds located in geographically and climatically distinct zones in Australia, and to evaluate the antimicrobial susceptibility of the isolated bacteria. Quarter-level milk s les ( n = 419) were collected from 151 mastitis cases and 268 healthy controls originating from 18 dairy herds located in tropical (Northern Queensland), subtropical (Southeast Queensland) and temperate zones (Victoria) between March and June 2019. Milk s les were cultured, and the isolated bacteria were grouped into six groups: Enterobacteriaceae spp. Streptococcus spp. Staphylococcus aureus , non-aureus staphylococci (NAS) Bacillus spp. and Others. Mixed effects conditional logistic regression models were applied to quantify the association between the prevalence of each bacterial group and the herd zone and bulk milk tank somatic cell counts (BMTSCC). Of the 205 isolates, 102 (50%) originated from mastitis cases, and 103 (50%) from controls. Staphylococci were the most prevalent (NAS 32% and S. aureus 11%). Contagious mastitis bacteria were more prevalent in Victoria compared to Queensland dairy herds. NAS species ( P & 0.001) were less prevalent in herds with BMTSCC & ,000 cells/mL compared with herds with low BMTSCC ≤150,000 cells/mL. Enterobacteriaceae and Streptococcus spp. groups showed high resistance rates to 1 (51 and 47%, respectively), and 2 (11 and 23%, respectively), antimicrobials. More than one third of the Enterobacteriaceae (48%) and Others (43%) groups spp. were resistant to at least three antimicrobials. This study provided a unique opportunity to investigate the prevalence of mastitis-associated bacteria in clinical cases and in apparently healthy controls. The findings of this study help inform mastitis control and antimicrobial stewardship programs aimed to reduce the prevalence of mastitis and antimicrobial resistance in dairy herds.
Publisher: Wiley
Date: 27-03-2017
DOI: 10.1111/AVJ.12573
Abstract: To determine the effects of ovarian structures present at Ovsynch™ enrolment, disease history, lactation variables and times bred on pregnancy per fixed-time artificial insemination (FTAI) following fixed-time insemination after Ovsynch and to determine the relationship between the size of ovarian follicular structures and concurrent presence of a corpus luteum (CL). The study was conducted in a 3000-cow Holstein dairy herd. Over a 6-month period, 886 non-pregnant cows were examined by transrectal ultrasound and enrolled into 1132 Ovsynch events. Enrolled cows were synchronised using an Ovsynch-56 protocol. At enrolment, both ovaries were scanned by transrectal ultrasound to identify and record the presence and size of ovarian structures. Cows that did not return to oestrus were pregnancy tested 32-38 days post-insemination. Univariable and multivariable generalised linear mixed models (GLMMs) were used to determine the effect of each variable on pregnancy per FTAI. A univariable GLMM was also used to analyse the relationship between size of the dominant follicular structure and concurrent presence of a CL. CL size (P = 0.039) and presence of a luteal cyst (P = 0.002) at Ovsynch enrolment significantly increased the odds of pregnancy. Occurrence of lameness (P = 0.035) or mastitis (P = 0.008) between calving and enrolment significantly decreased the odds of pregnancy. Neither the presence nor size of a follicular structure significantly affected the odds of pregnancy, although cows with larger follicular structures were less likely to have a concurrent CL (P < 0.001). Presence of luteal tissue at Ovsynch enrolment and recent disease events affected pregnancy per FTAI in cows inseminated after Ovsynch.
Publisher: Informa UK Limited
Date: 15-02-2021
DOI: 10.1080/00480169.2020.1850368
Abstract: To investigate the association between the density of wooden hoof blocks and resistance to wear in pasture-based dairy herds, and to assess the density of commercially available wooden hoof blocks. Three types of wooden hoof blocks with different densities (low, medium and high) were attached to 36 lactating dairy cows with parity ≤2 and sound locomotion (score ≤2 on a scale of 1-4). The height of wooden blocks was measured in three different regions, front, abaxial and caudal on Days 7, 11, 14, 18, 21, 25 and 28 after application. Due to the loss of low-density wooden blocks, the data for these blocks were analysed for only two measurements on Days 7 and 11. The data for medium and high-density wooden blocks were analysed from Days 7-25. A linear mixed model with repeated measures was used to analyse the repeated observations. Height, density and surface area of commercially available hoof blocks (n = 19) were measured and compared to the blocks used in this study. The magnitude of wear, in the front and the abaxial point of the blocks were greater in blocks made of low-density wood compared to those made of medium and high-density wood (p < 0.001). The amount of wear increased over time for all groups (p < 0.001). Wood density was negatively associated with wear and loss. Measurements of commercial wooden blocks revealed that the 13/19 (63%) had lower density and 12/19 (68%) less surface area than the wooden blocks with medium density used in this study. In this study, the density of the wood was significantly associated with the longevity of hoof blocks when applied to hooves of pasture-based dairy cows. The longevity of the wooden hoof blocks applied to treat lame cows plays a significant role in the healing of the claw horn lesions. The density of a wooden hoof block affects the rate of wear of the block, and this should be considered by manufacturers and those treating lame cows.
Publisher: Wiley
Date: 21-04-2020
DOI: 10.1111/AVJ.12950
Publisher: Wiley
Date: 27-08-2017
DOI: 10.1111/AVJ.12621
Abstract: To determine if insemination site or pre-ovulatory follicle diameter at fixed-time artificial insemination (FTAI) affects the odds of pregnancy when heifers are inseminated with sexed semen. The study was conducted in 422 Holstein heifers enrolled into 531 inseminations. Inseminations were randomly allocated to 1 of 16 treatment combinations involving three variables: semen type (sexed vs non-sexed), insemination site (uterine horn vs uterine body) and one of four sires. Ovaries were examined by transrectal ultrasound prior to FTAI to determine the follicle diameter and location. AI technician, times bred, age, weight and temperature-humidity index were also recorded. Pregnancy diagnosis was conducted 29 days post-insemination. Follicle diameter and body weight were categorised according to arbitrary cut-points. Each variable was analysed by logistic regression to determine the effect on pregnancy per AI and compare between sexed and non-sexed inseminations. Insemination site did not affect pregnancy per AI for either sexed (P = 0.528) or non-sexed (P = 0.886) inseminations. Heifers with an 18-22 mm follicle had better odds of pregnancy than heifers that did not (odds ratio (OR) 1.45, 95% confidence interval (CI) 1.004-2.09), although no effect was detected for only sexed or only non-sexed inseminations. Heifers weighing 310-370 kg had a higher pregnancy per AI than heifers weighing > 370 kg for non-sexed inseminations (P = 0.004) and sexed semen from sire 4 caused lower odds of pregnancy than semen from sire 1 (OR 0.40, 95% CI 0.18-0.89). Insemination site did not affect pregnancy per AI, but heifers with an 18-22 mm pre-ovulatory follicle at insemination had better odds of pregnancy for both sexed and non-sexed inseminations.
Publisher: Wiley
Date: 11-03-2020
DOI: 10.1111/AVJ.12933
No related grants have been discovered for Shahab Ranjbar.