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Table 1: Classification of dystocia studies according to scores of dystocia Advances in Animal and Veterinary Sciences 2 (7): 381 – 389 http://nexusacademicpublishers.com/journal/4 The articles selected were generally American or European as shown in Table 2 and 3. Thirty papers were used to evaluate the impact of primiparous and multiparous cows on dystocia and nineteen papers for stillbirth. The scoring of dystocia was not constant in all papers, whereas stillbirth was recorded as dichotomous. The definition of dystocia was not standardized across studies (Table 1). Most studies classified dystocia within 5 categories including unassisted, easy, moderate, difficult, and very difficult. Some studies were recorded dystocia with four categories: = easy (non– assisted), 2 = moderate assistance (veterinarian called as precaution), 3 = difficult, 4 = very difficult with veterinary assistance. Some else recorded dystocia with three categories: no assist, easy and hard or two categories: unassisted and assisted. Study name No. of category Study name No. of category Cady and Burnside (1982) 3 Ansari-Lari (2007) 4 Martinez et al., (1983) 5 Lombard et al., (2007) 4 Djemali et al., (1987) A 5 de Maturana et al., (2007) 5 Djemali et al., (1987) B 5 Gonzalez–Recio et al., (2007) 4 Weller et al., (1988) 2 Lopez et al., (2007) 5 Lin et al., (1989) 2 Wall et al., (2008) 5 Berger (1994) 5 Wiggans et al., (2008) 5 Dematawewa and Berger (1997) 5 Fiedlerova et al., (2008) 3 Meyer et al., (2001) 5 Olson et al., (2009) 5 Johanson and Berger(2003) 5 Van Plet et al., (2009) 6 Steinbock et al.,(2003) 2 Gevrekci et al., (2011) 4 van Tassell et al.,(2003) 5 Hébert et al., (2011) 4 Adamec et al.,(2006) 5 Eaglen et al., (2012) 4 Heins et al., (2006) 5 Atashi et al., (2012a) 5 Steinbock (2006) 2 Dhakal et al., (2013) 5 Table 2: A summary of dystocia studies Study name Primiparous Primiparous Multiparous Multiparous Events Total–N Events Total–N Country Cady and Burnside (1982) 1851 7845 1833 21661 Canada Martinez et al., (1983) 8033 29130 10964 107645 USA Djemali et al., (1987) A 20979 83919 38756 387565 USA Djemali et al., (1987) B 2126 11189 7828 130466 USA Weller et al., (1988) 8594 106751 4292 146973 Israel Lin et al., (1989) 292 1722 240 3186 USA Berger (1994) 15298 907915 9347 2732741 USA Dematawewa and Berger (1997) 13628 71618 3490 51096 USA Meyer et al.,(2001) 31820 167472 29932 498869 USA Johanson and Berger (2003) 586 1558 325 2775 USA Steinbock et al., (2003) 34146 411409 12653 281193 Sweden van Tassell et al., (2003) 588838 2612288 756380 7582809 USA Admec et al., (2006) 9982 47615 12504 170568 USA Heins et al., (2006) 61 371 26 303 USA Steinbock (2006) 28954 804268 16829 673150 Sweden Ansari-Lari (2007) 147 815 135 1861 Iran Lombard et al., (2007) 486 2574 359 5214 USA de la Calle (2007) 1008 29567 419 22660 Spain Gonzalez–Rico et al., (2007) 3212 62134 1717 71547 Spain Lopez et al., (2007) 887 25810 482 27543 Spain Wall et al., (2008) 7117 37261 2343 23265 UK Wiggans et al., (2008) 647529 4035953 766362 11101267 USA Fiedlerova et al., (2008) 14047 158192 10364 251063 Czech Olson et al., (2009) 31 86 18 155 USA Van Plet et al.,(2009) 4813 42968 3746 114913 Netherlands Gevrekci et al.,(2011) 833 4495 1169 14944 Turkey Hébert et al., (2011) 1801 138538 2087 279845 Canada Eaglen et al.,(2012) 8680 30640 9241 54744 UK Atashi et al.,(2012a) 6265 63041 1987 37587 Iran Dhakal et al.,(2013) 11 51 10 139 USA Al–Samarai (2014). Meta–analysis on Dystocia and Stillbirth 382 ISSN: 2307–8316 (Online); ISSN: 2309–3331 (Print)
Standard Error Table 3: A summary of stillbirth studies Advances in Animal and Veterinary Sciences 2 (7): 381 – 389 http://nexusacademicpublishers.com/journal/4 Study name Primiparous Primiparous Multiparous Multiparous Events Total–N Events Total–N Country Weller et al., (1988) 8177 106751 5600 146973 Israel Harber ( 1992) 119489 1048145 147075 2779295 Netherlands Meyer et al., (2001) 18417 167472 28242 498869 USA Johanson and Berger(2003) 195 1558 127 2775 USA Steinbock et al., (2003) 29210 411409 7592 281193 Sweden Bar (2005) 437 6570 406 11178 Israel Adamec et al.,(2006) 3399 28862 2841 45915 USA Heins et al., (2006) 56 371 37 303 USA Steinbock (2006) 32171 804268 12790 673150 Sweden Bicahlo et al.,(2007) 566 5288 330 8320 USA Lombard et al., (2007) 324 2574 318 5214 USA Cole et al., (2007) 108897 1773099 258957 5247452 USA Wall et al., (2008) 4583 37261 1402 23265 UK Wiggans et al., (2008) 223792 1965653 251176 5375384 USA Olson et al., (2009) 18 86 8 157 USA Atashi (2011) 415 5205 318 7078 Iran Atashi et al., (2012b) 6805 126017 4500 179040 Iran Eaglen et al.,(2012) 3354 30640 2354 54744 UK Dhakal et al.,(2013) 8 51 18 139 USA 0.0 Funnel Plot of Standard Error by Log odds ratio 0.1 Figure 1: A funnel plot for detection bias of OR in dystocia 0.2 0.3 0.4 0.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 Log odds ratio Meta–analyses were conducted on dystocia and stillbirth using Comprehensive Meta–Analysis.V.2 software (2013), whereas forest plot was carried out by using MedCalc V.6 (2013). Guidelines for conducting appropriate meta– analysis were largely based on meta– Data Analysis Analysis of Potential Publication Bias A funnel plot: two modes were available, one which plots a study’s effect size against its standard error and another which plots effect size against precision. In the absence of bias the plot would be symmetric about the summary effect (Duval andTweedie2000): Test the rank correlation (Kendall’s tau) between the standardized effect size and the variances (or standard errors) of these effects (Begg and Mazumdar, 1994). Test the standardized effect (the regression of effect size divided by standard error on precision (inverse of standard error). Analysis of Heterogeneity Heterogeneity of the estimated OR was assessed using the Cochran’s Q statistic chi square test (Egger et al., 2001). If there was evidence of heterogeneity, then a random model (inverse variance) is preferred. The degree of heterogeneity was assessed by the I 2 (I squared) statistic. This describes the percentage of the variability in effect estimates that is due to heterogeneity rather than sampling error (chance) (Higgins et al., 2003). RESULTS AND DISCUSSION Effect of Primiparous and Multiparous on Dystocia Results shows that I 2 = 99.72, and P = 0.000. An I 2 value >50 may be considered indicative of substantial heterogeneity. In such case a random model is considered more suitable than fixed model (Rabiee et al., 2012). Estimated OR with a random model for dystocia is OR = 2.68, 95% CI 2.51 to 2.85 and the corresponding estimates in a fixed model is OR = 2.61, 95% CI 2.60 to 2.61 (Table 4). It's obvious from Figure (1) the presence of bias as the OR values were distributed asymmetrically. Pooled OR was Al–Samarai (2014). Meta–analysis on Dystocia and Stillbirth 383 ISSN: 2307–8316 (Online); ISSN: 2309–3331 (Print)
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