Browsing by Author "Bunyaga, A. S."

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Cryopreservation of dog semen as an alternative method to improved fertility in bitches: A review article
(Tanzania Veterinary Association, 2018-02-01) Bunyaga, A. S.; Kashoma, I. P.
Cryopreservation of dog semen facilitates the exchange of genes between populations and makes it possible to preserve genes from valuable males for an extended time. Although AI in dogs can help avert sexually transmitted diseases and reducing the chances of inbreeding, the technique is not routinely practised in most developing countries including Tanzania. Among the reasons are problems associated with cryopreservation. Cryopreservation of semen has a number of problems limiting its success and thus, affecting fertility in dogs as a whole. The common assisted reproductive technologies like AI in dogs are constrained by challenges in semen cryopreservation which partly is caused by freezing temperature, cryoprotectants and lifespan of spermatozoa. The purpose of this review is to study the possible ways which can improve cryopreservation of semen in dogs. Improving semen cryopreservation is not a one process; it involves a combination of factors with the ultimate goal of improving the outcome of semen cryopreservation in terms of conception rates in bitches, and thus, fertility in general. Cryopreservation parameters to improve include: type of ejaculate, insemination technique, storage, post thawing procedures, extenders, cryoprotectants, collection method and antioxidants. Several approaches have been recommended, including cryopreservation protocols, for instance freezing rates should be slow enough to allow the cells to minimize chemical potential and osmolality gradients across the plasma membrane, but fast enough to dehydrate the cell without exposing it to lethal salt concentrations. Moreover, the first ejaculates and the ejaculates from old dogs are to be discouraged if we need to improve fertility output under cryopreservation method. Thawing temperature of 70°C and above within a few seconds, have shown promising results. Possibly, this temperature is helpful to reduce the toxic nature of cryoprotectants. However, this review suggests the use of intrauterine method, and possibly innovation of new modification and training expertise would help to improve fertility in bitches. Nevertheless, more work is needed to accurately predict fertility of cryopreserved canine semen.
Photoperiodic control of seasonal breeding
(Open University of Tanzania, 2018) Bunyaga, A. S.; Makungu, M.
Photoperiod is a powerful synchronizer of seasonal changes in endocrine and metabolic physiology in vertebrates living in tropical to polar zone. The purpose of this review is to study the factors which are involved in the process of photoperiodism in control of seasonal breeding in birds and mammals. The gonadotropin-releasing hormone (GnRH) is crucial in seasonal breeding mammals and birds, whereby under the influence of thyroid hormone, triiodothyronine (T3), it stimulates the anterior pituitary gland to release gonadotropins responsible for maturation of reproductive organs. The process that leads to stimulation of GnRH production differs between birds and mammals. In birds, light is perceived by deep brain photoreceptors and long day induced thyroid-stimulating hormone (TSH) causes local T3 activation. In mammals, light is perceived by the eyes and melatonin which is secreted during the night from the pineal gland regulates TSH. Therefore eyes, pineal gland and melatonin are not essential for regulation of seasonal reproduction in birds. Despite the differences, birds and mammals are subjected to common features i.e. light exposure and TSH during photostimulation. Long photoperiod causes photostimulation followed by photorefractoriness. The latter, has been thought to occur due to the influence of prolactin. The initial gonadal regression which is encountered during photorefractoriness occurs while there is still releasable GnRH. The timing of photorefractoriness is influenced by food availability, temperature and social factors like songs. The dissipation of photorefractoriness occurs during short photoperiods and is characterized by an increase in hypothalamic GnRH
Prevalence and antimicrobial resistance in Campylobacter from different stages of the chicken meat supply chain in Morogoro, Tanzania
(Tanzania Veterinary Journal, 2015-01-12) Kashoma, I. P.; Mkomba, F. D.; Bunyaga, A. S.
Poultry are recognized as a main reservoir of Campylobacter spp. However, longitudinal studies investigating the persistence of Campylobacter on broilers and retail chciekn meat in Tanzania are rare. The aim of the current work was to evaluate the prevalence and antimicrobial susceptibility of Campylobacter spp. isolated from broiler farms and retail chicken meat. Eight hundred samples were collected from broilers aged 1 week to slaughter and retail chicken carcasses, consisting of 600 fecal droppings and 200 carcass rinses. The overall Campylobacter prevalence was 43.3% (381/880). The isolation rate of Campylobacter from chicken faeces was 41.5%, from carcasses at the farm was 51.0% and from carcasses from retail stores was 37.5%. Biochemical testing by hippurate hydrolysis identified 72.4% of all isolates as C. jejuni, 20.5% as C. coli, and 7.1% as other Campylobacter spp. Multiplex polymerase chain reaction confirmed 75.1% of all isolates as C. jejuni, 17.8% as C. coli, 4.2% as both, and 2.9% as other Campylobacter spp. Antimicrobial susceptibility testing using disk diffusion assay and broth micro-dilution method revealed resistance to: ampicillin (41% and 44%, respectively), ciprofloxacin (56 and 59%), erythromycin (17 and 18%), gentamicin (6% and 12%), streptomycin (20 and 23%), and tetracycline (62 and 63%). Resistance to azithromycin (9%), chloramphenicol (7%) and nalidixic acid (72%) was determined using the disk diffusion assay only. Up to 5% and 4% of all isolate tested were pan-susceptible, while, 67% and 40% showed multidrug resistance using the disk diffusion assay and the broth microdilution method, respectively. These results reinforce the need of efficient strategy implementation to control and reduce Campylobacter in chickens at production and slaughter levels, and the necessity to reduce the use of antimicrobials in poultry sector.
The use of fetal femur length for estimation of gestational age in cattle
(Tanzania Veterinary Association, 2017-12-07) Bunyaga, A. S.
The aim of the present research was to study the relationship between the femur and gestational age and thus generate an equation which would be able to estimate fetal age in cows. 23 dairy cows were examined every after one week transrectally using B−mode real−time ultrasound scanner with a 7.5MHz linear probe (Mindray DP 6600, Mindray Szechuan, China). The dairy cows were examined at Large Animal Research Unit of Massey University New Zealand between day 60 and day 120 of pregnancy. Ultrasonography examination commenced the 20th of July 2015 and was finished in September 2015. The predicted gestation age in dairy cows had a chance of being 21.7 days greater and 21.6 days less than actual gestational age. The findings from this study show there is a moderate positive linear correlation between femur length and gestational age in the dairy cows (R2 =0.64). However, this relation did not have good agreement to justify the use of equation developed to be used in estimation of gestational age.