Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations
Accurate prediction of bodyweight (BW) from measurable animal characteristics serves many practical purposes for livestock farmers in sub-Saharan Africa, where weighing scales are often impractical or unaffordable. A volume of literature is devoted to BW estimation using heart girth (HG) (circumf...
| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
| Language: | Inglés |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10568/180525 |
| _version_ | 1855529181718249472 |
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| author | Hawkins, James Broonsvort, Barend M.deC Odadi, W.O. Gurmu, Endale Balcha Garcia, Edward Assouma, M.H Dossa, L.H. Leitner, Sonja Arndt, Claudia |
| author_browse | Arndt, Claudia Assouma, M.H Broonsvort, Barend M.deC Dossa, L.H. Garcia, Edward Gurmu, Endale Balcha Hawkins, James Leitner, Sonja Odadi, W.O. |
| author_facet | Hawkins, James Broonsvort, Barend M.deC Odadi, W.O. Gurmu, Endale Balcha Garcia, Edward Assouma, M.H Dossa, L.H. Leitner, Sonja Arndt, Claudia |
| author_sort | Hawkins, James |
| collection | Repository of Agricultural Research Outputs (CGSpace) |
| description | Accurate prediction of bodyweight (BW) from measurable animal characteristics serves
many practical purposes for livestock farmers in sub-Saharan Africa, where weighing scales
are often impractical or unaffordable. A volume of literature is devoted to BW estimation
using heart girth (HG) (circumference of chest diameter behind front legs) as a main
predictor, yet most published equations are derived from narrowly defined animal samples
(e.g., single breeds, age classes, or production systems), limiting their applicability across
Africa’s diverse livestock populations.. Based on a large and geographically diverse
repeated measurement sample of African bovines (n = 6,434; 13,790 total measurements)
and caprines (n = 2,113; 6,049 total measurements) we developed prediction equations
specific to ruminant species (bovines, sheep, goats), breed (indigenous caprines or Bos
indicus bovines vs. crosses thereof with exotics or B. taurus), and production system
(extensive vs. semi-intensive) by segmenting regression formulae according to tertiles (equal
thirds) of HG. Segmentation by HG improved model fit at upper extremities of HG where
residual errors are typically highest. Among four regression formulae: linear, square root,
quadratic, Box-Cox -- Box-Cox consistently performed best across sub-samples of species,
breed, and system, with the exception of indigenous African sheep breeds (best fit using a
quadratic formula). Lines-of-best fit were characterized as convex, with Box-Cox lambda
parameters ranging from 0.141-0.788, a finding in general agreement with other studies
performing non-linear regression. At the extremes of HG segmented regression had superior
predictive accuracy, in particular, with as much as a 25% reduction in NRMSE relative to
non-segmented regression at the upper HG tertile. The contributions of this study are thus:
(i) provision of the most comprehensive, genetically and geographically diverse set of BW
prediction equations for African domestic ruminants to-date, and (ii) for bovines, using
segmented regression, BW prediction robust to the extremities of BW/HG, yielding
substantially improved prediction accuracy (NRMSE < 5%) over existing published formulae.
As Box-Cox formulae are most accurate but structurally complex, authors propose formula
transformations embedded directly on weigh-tapes or charts to maximize ease-of-use and to
enable scalable, low-cost, and accurate BW estimation for African production systems. |
| format | Preprint |
| id | CGSpace180525 |
| institution | CGIAR Consortium |
| language | Inglés |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| record_format | dspace |
| spelling | CGSpace1805252026-01-24T02:09:27Z Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations Hawkins, James Broonsvort, Barend M.deC Odadi, W.O. Gurmu, Endale Balcha Garcia, Edward Assouma, M.H Dossa, L.H. Leitner, Sonja Arndt, Claudia livestock body weight animal morphology production systems Accurate prediction of bodyweight (BW) from measurable animal characteristics serves many practical purposes for livestock farmers in sub-Saharan Africa, where weighing scales are often impractical or unaffordable. A volume of literature is devoted to BW estimation using heart girth (HG) (circumference of chest diameter behind front legs) as a main predictor, yet most published equations are derived from narrowly defined animal samples (e.g., single breeds, age classes, or production systems), limiting their applicability across Africa’s diverse livestock populations.. Based on a large and geographically diverse repeated measurement sample of African bovines (n = 6,434; 13,790 total measurements) and caprines (n = 2,113; 6,049 total measurements) we developed prediction equations specific to ruminant species (bovines, sheep, goats), breed (indigenous caprines or Bos indicus bovines vs. crosses thereof with exotics or B. taurus), and production system (extensive vs. semi-intensive) by segmenting regression formulae according to tertiles (equal thirds) of HG. Segmentation by HG improved model fit at upper extremities of HG where residual errors are typically highest. Among four regression formulae: linear, square root, quadratic, Box-Cox -- Box-Cox consistently performed best across sub-samples of species, breed, and system, with the exception of indigenous African sheep breeds (best fit using a quadratic formula). Lines-of-best fit were characterized as convex, with Box-Cox lambda parameters ranging from 0.141-0.788, a finding in general agreement with other studies performing non-linear regression. At the extremes of HG segmented regression had superior predictive accuracy, in particular, with as much as a 25% reduction in NRMSE relative to non-segmented regression at the upper HG tertile. The contributions of this study are thus: (i) provision of the most comprehensive, genetically and geographically diverse set of BW prediction equations for African domestic ruminants to-date, and (ii) for bovines, using segmented regression, BW prediction robust to the extremities of BW/HG, yielding substantially improved prediction accuracy (NRMSE < 5%) over existing published formulae. As Box-Cox formulae are most accurate but structurally complex, authors propose formula transformations embedded directly on weigh-tapes or charts to maximize ease-of-use and to enable scalable, low-cost, and accurate BW estimation for African production systems. 2025-12-22 2026-01-23T13:27:46Z 2026-01-23T13:27:46Z Preprint https://hdl.handle.net/10568/180525 en Open Access application/pdf application/vnd.openxmlformats-officedocument.spreadsheetml.sheet Hawkins, J.W., Broonsvort, Barend M.deC. Odadi, W.O., Gurmu, E.B., Cabezas-Garcia, E.H.Assouma, M.H., Dossa, L., Leitner, S.M., Arndt, C. 2025. Scalable, low-cost livestock bodyweight estimation for Sub Saharan African production systems using robust segmented heart-girth equations. Social Science Research Network (SSRN) |
| spellingShingle | livestock body weight animal morphology production systems Hawkins, James Broonsvort, Barend M.deC Odadi, W.O. Gurmu, Endale Balcha Garcia, Edward Assouma, M.H Dossa, L.H. Leitner, Sonja Arndt, Claudia Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations |
| title | Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations |
| title_full | Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations |
| title_fullStr | Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations |
| title_full_unstemmed | Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations |
| title_short | Scalable, low-cost livestock bodyweight estimation for Sub-Saharan African production systems using robust segmented heart-girth equations |
| title_sort | scalable low cost livestock bodyweight estimation for sub saharan african production systems using robust segmented heart girth equations |
| topic | livestock body weight animal morphology production systems |
| url | https://hdl.handle.net/10568/180525 |
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