Abstract
Background Calf mortality has been a major cause of economic losses in the dairy industry in Ethiopia. The condition results in a significant drop in the number of replacing heifers and bulls for sustainable dairy business. Reports on calf mortality with a wide range of prevalence are rising in the country; however, a pooled prevalence of this condition has not been established. Thus, this systematic review and meta-analysis aimed to quantitatively estimate the pooled prevalence of calf mortality in Ethiopia. Methods Meta-analysis was carried out to obtain the pooled prevalence of calf mortality in Ethiopia. A comprehensive literature search was carried out on PubMed, African Journals Online, CAB, Web of Science Direct, and Google Scholar. Eligible studies were selected based on predefined inclusion and exclusion criteria. Moderators such as the study area, breed of calf, study design, agroecology, and year of study article published were used as a milestone of data extraction. The random-effect model was used to estimate pooled prevalence. Publication bias and the variation in prevalence estimates attributed to heterogeneity were also assessed. Results Twenty-five original research papers on the prevalence of calf mortality in various parts of Ethiopia were included. The reported prevalence of calf mortality was between 0.9% and 37%. The pooled prevalence of calf mortality in the country was 14.79%, and the pooled calf mortality estimate across studies for the entire period regarding 1991 to 2000, 2001 to 2010, 2011 to 2016, and 2017 to 2020 was 26.54%, 17.03%, 14.21%, and 11.23%, respectively. Analysis of study subgroups and location revealed significant variations in prevalence. High heterogeneity was observed in the pooled estimates and even after the subgroup meta-analysis. The funnel plots and Egger's regression asymmetry coefficient (b = −1.0434) (95% CI = −1.49, −0.59; p value of 0.012) did suggest the presence of publication bias. There was also an indication of missing studies that could be incorporated by Duval and Tweedie's trim and fill method where they might fall on a funnel plot and visualize them in an attempt to increase the plot's symmetry. Analyses also suggest that calf breed, sample size, and study location are likely to be moderators of calf mortality prevalence in Ethiopia. Conclusion This finding shows that calf mortality is widespread and could result in considerable economic losses for the dairy industry in Ethiopia. Inevitably, a significant reduction in calf mortality prevalence has been observed in recent years since 2010, but the reduction has not yet reached an economically tolerable level. Calf breed susceptibility contributed to the high prevalence. Therefore, interventions for increasing calf health and performance should be focused on minimizing calf mortality on farm and animal levels.
Highlights
Ethiopia has the largest livestock population, being the first in Africa and the tenth in the world [1, 2]. e livestock sector of this huge population plays an important role in the national economy as well as in the socioeconomic development of millions of rural smallholder farmers as income, employment generation, and poverty alleviation [3].the sector contributes to 15% of export earnings and currently supports the livelihoods of 80% of the rural population [1, 4].e dairy industry being part of the livestock production unit has been recognized as one of the most prominent industries in the pursuit to attain food security and good welfare [5]
About 30 reports were dissimilar, having unrepresentative sample size, inappropriate study designs, and different agroecology with the disproportionate sample; they were excluded together with the lack of data on other required predictors. is between-studies variability nature reduced substantially our datasets to be included in the meta-analysis. e studies include papers that were conducted in the period from 1991 to 2020. e total number of calves enrolled and died in the studies was 13,762 and 2,571, respectively. e sample size ranged from 30 to 1829 calves (mean: 529; standard error (SE): ±90). e range prevalence of calf mortality documented in the literature varied from 0.9% to 37.3% (mean: 17.4%; standard error (SE): ±1.8%) [6, 9, 10, 15,16,17]
Geographical Distribution of Included Studies in Ethiopia. e reports were collected from studies conducted in six regional states, namely, Amhara, Afar, Oromia, South Nations Nationalities and Peoples Region, Somali, and Tigray, between 1991 and 2020
Summary
Calf mortality has been a major cause of economic losses in the dairy industry in Ethiopia. e condition results in a significant drop in the number of replacing heifers and bulls for sustainable dairy business. Calf mortality has been a major cause of economic losses in the dairy industry in Ethiopia. Us, this systematic review and meta-analysis aimed to quantitatively estimate the pooled prevalence of calf mortality in Ethiopia. Meta-analysis was carried out to obtain the pooled prevalence of calf mortality in Ethiopia. Eligible studies were selected based on predefined inclusion and exclusion criteria Moderators such as the study area, breed of calf, study design, agroecology, and year of study article published were used as a milestone of data extraction. Analyses suggest that calf breed, sample size, and study location are likely to be moderators of calf mortality prevalence in Ethiopia. Is finding shows that calf mortality is widespread and could result in considerable economic losses for the dairy industry in Ethiopia. Calf breed susceptibility contributed to the high prevalence. erefore, interventions for increasing calf health and performance should be focused on minimizing calf mortality on farm and animal levels
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