Feyisa  Bekuma, Tadele  Tolosa, Worku  Tiger, 
    Heifer Mastitis: Prevalence, Assessments of Risk Factors and Antimicrobial Suseptablity Test
on Major Bacterial Isolate in Centeral Ethiopia,
    Journal of Animal and Veterinary Advances,
    Volume 20,Issue 2,
    2021,
    Pages 50-62,
    ISSN 1680-5593,
    javaa.2021.50.62,
    (https://makhillpublications.co/view-article.php?doi=javaa.2021.50.62)
    Abstract: Heifer mastitis causes detrimental mammary
gland development affecting the subsequent lactating
stages, udder health and related culling hazard resulting in
significant economic losses to the dairy development
sector. Across sectional study was conducted from June
2011 to March 2012 on cross breed heifers in Debre-zeit
and Sebeta towns to estimate the prevalence of heifer
mastitis, isolate bacteria causing mastitis and test their
antimicrobial susceptibility. One hundred fifty eight (158)
heifers were able to include from one hundred forty nine
(149) cooperative smallholder dairy farms during the
study period. From the total of 158 heifers sampled,
46(29.1%) were positive for mastitis (9.5% clinical and
19.6% subclinical cases). Identification of the bacteria
on primary culture was made on the basis of colony
morphology, hemolytic characteristics, gram stain
reaction including shape and arrangements of the bacteria,
catalase and oxidation and fermentation (o-f) test and
further differentiation within the species level were made
by selective media. The most frequently isolated bacteria
from quarter milk samples in for clinical and subclinical
mastitis were 7(24.1%) and 22 (75.9%) CNS, 7(26.91%)
and 19(73.1% ) <i>Staphylococcus aureus</i> and 4(22.2%) and
14(77.8%) <i>E. coli</i>, respectively. Other bacterial isolates
were <i>Streptococcus agalactiae</i> (1(11.1%) and 8(88.9%),
<i>Kelebsella pneumonia</i> (3(37.5%) and 5(62.5%)), <i>Bacillus
cerus</i> (1(16.7%) and 5(8.3.3%)), actinomycet pyogens
(1(25%) and 3(75%)), <i>Streptococcus dysagalactiae</i> 0 and
3(100%), <i>Entroccoccus feacalise</i> (0 and 3(100%)) and
<i>Streptococcus uberis</i> (0 and 3(100%)) for clinical and
subclinical mastitis, respectively. The univariate logistic
regression showed that among the risk factors considered,
age, heifer status, mastitic milk fed to calves, body
condition scoring, usage of waste disposal and udder
hygiene had significant effect on the prevalence of subclinical
mastitis. However, after multivariate analysis,
only age (OR = 2.1; CI, 1.5-2.9), mastitic milk fed to
calves (OR = 2.3; CI, 1.5-3.4), udder hygiene (OR = 1.9;
CI, 1.4-2.5) and usage of waste disposal (OR = 2.7; CI,
1.6-4.4), had significant effect. The antimicrobial
susceptibility test showed for the majority of bacterial
isolates including the major pathogens had 75-100%
susceptibility pattern. CNS and <i>Streptococcus
dysagalactiae</i> were the species which showed 100%
susceptibility for all of the antimicrobials tested while the
remaining species had varying levels of susceptibility
(50-100%). Among isolates <i>Staphylococcus aureus</i> show
relatively lower susceptibility for almost all antimicrobials
used. Streptomycin and Erythromycin was the most
effective antibiotic followed by Sulfisoxazole and
Ampicillin. The presence of mastitis in heifer in early
age indicates important economic losses. Therefore,
awareness creation at the smallholder dairy farm on the
economic significance of heifer mastitis, risk factors that
plays vital role in establishment and flourishment of
potential pathogen and use of dry cow therapy before
calving will help in reducing mastitis in heifer. Moreover,
further studies on what extent the causative pathogen and
the host itself affect the persistence of intramammary
infection during calving and early lactating heifers and
evaluation of other risk factors in depth will merits the
dairy farms.
    Keywords: Prevalence;heifer Mastitis;bacterial isolates;antibiotic;susceptibility;central Ethiopia