Molecular characterization of Staphylococcus aureus strains in bovine mastitis milk in Bangladesh

Staphylococcus aureus is a common causative agent of bovine mastitis in dairy herds worldwide. This study was designed to assess the prevalence of mastitis in cows through screening tests and molecular characterization of Staphylococcus aureus strains. Out of 175 randomly screened cows, mastitis was detected in 50 cows by California Mastitis Test (CMT), and from those mastitic cows, 200 quarter milk samples were collected for subsequent culture and PCR based identification. The herd, cow and quarter level prevalence of mastitis was 73.3, 28.6 and 29.5% respectively, and subclinical mastitis (SCM) was the predominant type in all cases. According to bacteriology the overall prevalence of herd, cow and quarter level Staphylococcus aureus mastitis was 72.7, 74.0 and 62.0%, respectively, and the pathogen was mostly associated with clinical mastitis (CM). Cows breed, parity, daily milk yield, regular teat dipping, and dry cow therapy were significantly associated (P < 0.05) risk factors for mastitis onset. This study identifies 145 Staphylococcus aureus isolates which varied greatly with the categories of mastitis (higher in CM), udder quarter location (highest in right rear quarters), and to a lesser extent in the study areas (P < 0.05). Antimicrobial susceptibility testing revealed that 79.3% Staphylococcus aureus strains were resistant to at least one antimicrobial, 49.0% to two or more antimicrobials, and clinical isolates showed more resistance to all tested antibiotics. The highest resistance rate was found to oxytetracyclin, and no resistance to ceftriaxone and azithromycin. Seven enterotoxin gene profile were detected in the tested isolates, and mecA was found in 20.0% isolates indicating the emergence and spread of methicillin-resistant Staphylococcus aureus (MRSA). The isolates were carrying genes in combination, and were found higher in SCM cases. In this study, plasmids (>23 kb to 2.9 kb) were detected in 70.3% strains, and 54.9% plasmid bearing strains were multiple drug resistant (MDR). Thus, the high prevalence of Staphylococcus aureus mastitis is an important concern for diary industry of Bangladesh since the strains of this pathogen is becoming more resistant to commercially available antimicrobials, and this is an alarming concern for both animal and public health.

Effect of administration of vitamin E, selenium and antimicrobial therapy on incidence of mastitis, productive and reproductive performances in dairy cows

Administration of vitamin, mineral and antimicrobials at the end of lactation plays potential role in preventing mastitis in dairy cows. A total of 255 cows dividing into five groups (A = 50, B = 50, C = 50, D = 50 and E = 55) at their late gestation period were selected to explore the effect of vitamin E, selenium and antimicrobial therapy on mastitis incidence, their productive and reproductive performances. Each cow of group A received α-tocopherol + sodium selenite orally daily for last 30 days before calving, while each cow of group B, C and D was treated with α-tocopherol + sodium selenite intramuscular injection, procaine penicillin + neomycin sulfate, and dicloxacillin sodium intramammary infusions at Day 30-20 before calving, respectively. Group E cows served as untreated control. California mastitis test (CMT) revealed that 70.0%, 76.0%, 84.0% and 100.0% cows in group A, B, C and D, respectively were free from new intramammary infections (IMIs) during early lactation period. The bacteriological results showed highest IMIs rates (76.3%) in group E and lowest IMIs (2.0%) in group D (P < 0.05). Staphylococcus aureus and Escherichia coli were the most predominant udder pathogens in all groups except group D (only CNS). The mean IMIs incidence (20.5%) was significantly lower in treated cows (P < 0.001). The treated cows had higher cure rates (81.9%) than control cows (23.1%) and overall efficacy of treatments on cure rates was 71.8% for all mastitis pathogens (P < 0.0001). The productive and reproductive performances of the treated cows at postpartum and early lactation period remained always higher than their non-treated counterparts (P < 0.001). A number of cow and herd related factors were identified to be significantly associated with mastitis (P < 0.001). The results concluded that antimicrobial therapy had more beneficial effect in preventing mastitis over vitamin-mineral administration and intramammary infusion with dicloxacillin sodium remained as the best effective preventive strategies for mastitis in dairy cows.

Factors affecting the first service conception rate of cows in smallholder dairy farms in Bangladesh

The successful outcome of an insemination is a combination of both male and female fertility-linked factors. We investigated the first service conception rate of cows at artificial insemination (AI) in the smallholder dairy farms in Bangladesh. Frozen straws were prepared from ejaculates of Bos indicus (n = 7) and Bos indicus × Bos taurus (n = 7) AI bulls. Fertility was determined from 6101 first services in cows that were performed by 18 technicians in four regions between April 2004 and March 2005. Pregnancy was diagnosed by rectal palpation between 60 and 90 days post-insemination. The Asian version of Artificial Insemination Database Application (AIDA ASIA) was used for bulls-, cows- and AI-related data recording, and later retrieved for analysis. The mean ± SD number of inseminations performed from individual bulls and their conception rates were 436.0 ± 21.6 and 50.7 ± 1.9%, respectively. Logistic regression demonstrated body condition scores (BCS), heat detection signs, months of AI and their interactions had greatest effects (odds ratios: 1.24-16.65, p < 0.04-0.001) on first service conception rate in cows. Fertility differed (p < 0.02-0.001) between the regions, previous calving months, months of AI, BCS, parity and heat detection signs of cows. Inseminations based on mounting activity (n = 2352), genital discharge (n = 3263) and restlessness and/or other signs (n = 486) yielded a conception rate of 53.6%, 48.8% and 50.1%, respectively (p < 0.05). Conception rate between technicians ranged between 43.4% and 58.6% (p < 0.05). The days interval from calving to first service (overall mean ± SD = 153.4 ± 80.6) had relationship (p < 0.001) with BCS, months of previous calving and parity of the cows. Fertility at AI in smallholder farms can be improved by training farmers on nutrition and reproductive management of the cows.

130 FLAVANOID INCREASES THE IN VITRO DEVELOPMENTAL ABILITY OF CLONED AND PARTHENOGENETIC PORCINE EMBRYOS

Flavonoid has anti-oxidant properties and has been shown to protect cells against oxygen radical damage. This study therefore, evaluated the effect of flavonoid on the in vitro development ability of porcine embryos produced by parthenogenesis (PA) or somatic cell nuclear transfer (SCNT). Porcine embryos were produced from abattoir-derived prepubertal oocytes either by PA or SCNT of fetal fibroblast into enucleated oocytes essentially as we described earlier (Gupta et al. 2008 Mol. Reprod. Dev. 75, 588–597). One-cell embryos were subsequently cultured in NCSU23 + 0.4% polyvinyl alcohol supplemented with or without 10 μm flavanoid for 7 days at 39°C in a humidified atmosphere of 5% CO2 in air. Results showed that the presence of flavonoid in the culture medium increased (v. controls) the rate of blastocyst in both PA (31.7 ± 4.0 v. 20.4 ± 2.0%) and SCNT (20.6 ± 2.5 v. 12.2 ± 2.9%) groups, respectively (P < 0.05). These blastocysts also had higher ability to hatch (PA: 53.7 ± 3.6 v. 34.0 ± 2.4%; SCNT: 70.9 ± 2.5 v. 45.7 ± 2.9%) and contained higher cell number (PA: 38.9 ± 2.0 v. 31.3 ± 2.1; SCNT: 37.5 ± 2.0 v. 29.7 ± 2.5) than those of control groups (P < 0.05). Western blot analysis of parthenogenetic blastocysts showed that, flavonoid also reduced the expression of caspase-3 and p38 mitogen-activated protein kinase (MAPK) proteins by 3.1 ± 0.1 and 7.7 ± 0.2 fold, respectively while expression of ERK1/2 protein was increased by 4.7 ± 2.3 fold. The 2′,7′-dichlorofluorescene fluorescence staining of embryos further revealed that the activity of reactive oxygen species (ROS) was significantly reduced in flavonoid treated embryos by 2 fold(P < 0.05). These data therefore, suggest that flavonoid may improve the in vitro development rate and quality of porcine embryos by reducing ROS activity and change in protein expression.

64 INCREASED REACTIVE OXYGEN SPECIES ACTIVITY IN PORCINE OOCYTES AND ZYGOTES VITRIFIED BY SOLID SURFACE VITRIFICATION

This study investigated the effect of reactive oxygen species (ROS) activity on the viability and fertilization rate of porcine IVM oocytes and on the developmental competence of IVF zygotes after solid surface vitrification (SSV). The SSV was performed essentially as we described earlier (Gupta MK et al. 2007 Theriogenology 67, 238–248). Briefly, matured oocytes having first polar body or zygotes having second polar body were equilibrated in TCM-199 medium supplemented with 20% (v/v) fetal bovine serum (FBS), 2% (v/v) dimethyl sulfoxide (DMSO), and 2% (v/v) ethylene glycol (EG) for 10 to 15 min. Equilibrated oocytes/zygotes were then rinsed 3 times (<30 s) in vitrification solution consisting of 17.5% (v/v) EG, 17.5% DMSO, 5% (w/v) polyvinylpyrrolidone, 13.7% (v/v) sucrose, and 20% (v/v) FBS in HEPES-buffered TCM-199 medium and then placed in groups of 10 to 15 oocytes/zygotes per 1- to 2-μL droplet onto aluminum foil kept directly over the liquid nitrogen. Vitrified oocytes/zygotes were then directly plunged in liquid nitrogen. Warming was performed in 2 steps in 0.4 and 0.2 m sucrose solution, each for 5 min. Nonvitrified, untreated oocytes/zygotes were used as controls whereas oocytes/zygotes treated with cryoprotectants only were used as toxicity controls (TC). The viability was evaluated by morphological appearance and fluorescein diacetate staining, and ROS level was assessed by 2′,7′-dichlorofluorescene fluorescence staining. Results showed that the percentages of live oocytes (75.0 ± 1.3%) and zygotes (85.5 ± 1.4%) in the SSV group were significantly lower than those of control (100.0 ± 0.0%, 100.0 ± 0.0%) and TC groups (97.3 ± 2.4%, 96.2 ± 0.6%), respectively. Similarly, the ROS levels were significantly greater in SSV groups than in control groups (P < 0.05). Addition of antioxidant (50 μm β-mercaptoethanol) to vitrification and culture media reduced the level of ROS in both oocyte and zygote groups, but did not improve the percentage of live oocytes (73.4 ± 2.2%) and zygotes (88.1 ± 3.7%) after warming. No beneficial effect of antioxidant was observed on the fertilization rate of vitrified oocytes. However, it did improve the cleavage rates of vitrified oocytes (30.0 ± 0.3% v. 21.3 ± 0.8%) and zygotes (64.2 ± 0.6% v. 54.3 ± 0.7%). These data suggest, therefore, that an increase in ROS activity may be associated with poor developmental competence of vitrified oocytes and embryos.

Crossbred bull selection for bigger scrotum and shorter age at puberty with potentials for better quality semen

Shortening age at puberty of crossbred breeding bull is an important issue in the tropics. This study aimed at selecting crossbred bulls at earliest possible age with bigger scrotum and potential for donating quality semen. One hundred and 31 pre-joining crossbred bulls of Central Artificial Insemination Laboratory, Saver, Dhaka were examined. The bulls being trained by seeing semen collection from mature bulls were allowed ejaculation into the artificial vagina at homosexual mount during a 20 min time at three occasions, every three months. Eighty one of 131 bulls produced at least one ejaculate during the study and their mean +/- SD age and scrotal circumference (SC) were 20.3 +/- 4.7 months and 28.2 +/-2.7 cm, respectively. Bulls' body weight, body condition score (BCS) and SC influenced the attainment of their puberty (p < 0.05). Bull's body weight had positive effects on scrotal circumference and ejaculate volume (p < 0.05). Scrotal circumference positively influenced the percentages of normal spermatozoa (p < 0.05). Scrotal skin-fold thickness negatively influenced the proportion of spermatozoa with normal head (p < 0.05). Based on age at first ejaculate and SC, 29.6% bulls (n = 24) were selected by cluster analysis. Selected bulls had mean +/- SD age 17.9 +/- 2.2 months, body weight 287.3 +/-48.6 kg, SC 30.5 +/- 1.5 cm, ejaculate volume 3.4 +/- 1.3 ml, sperm motility 50.8 +/- 17.2%, total spermatozoa per ejaculate 2541.9 +/- 1699.2 million and normal spermatozoa 81.5 +/-14.5%. The selected pubertal bull group was different from the unselected pubertal bulls at MANOVA (p < 0.0001). About 30% of pubertal crossbred bulls can be selected with shorter age and larger scrotum at puberty under conditions prevailed in Bangladesh.