Background Crossbreeding is successfully implemented worldwide to improve animal productivity and adaptability. However, recurrent failures of crossbreeding programmes in African countries imply the need to design effective strategies for the predominant smallholder production systems. Methods A comprehensive simulation procedure mimicked body weight (BWL) and tick count (TCL) incidence in a local taurine cattle breed and in an exotic indicine beef cattle breed (BWE and TCE, respectively). The two breeds were crossed to produce F1 and rotational animals. Additionally, synthetic breeds were created by applying four schemes defined as farm bull (FB), intra-village bull (IVB), exchanged-village bull (EVB), and population-wide bull (PWB) scheme. These schemes reflect different strategies to select and allocate bulls to smallholder farms. The different crosses were compared with the local breed over 20 generations by varying the genetic correlation between the traits (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12711_2025_952_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="16" /> </InlineMediaObject> <EquationSource Format="TEX">${r}_{g}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>r</mi> <mi>g</mi> </msub> </math></EquationSource> </InlineEquation> = − 0.4, 0, 0.4), genotype-by-environment effects (GxE) between local and exotic environment (<InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12711_2025_952_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="31" /> </InlineMediaObject> <EquationSource Format="TEX">${r}_{g\times e}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>r</mi> <mrow> <mi>g</mi> <mo>×</mo> <mi>e</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> = 0.4, 0.6, 0.8), and the relative emphasis of TCL compared to BWL in a selection index (SI_TCL10%, SI_TCL30%, SI_TCL50%). Results Regardless of <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12711_2025_952_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="16" /> </InlineMediaObject> <EquationSource Format="TEX">${r}_{g}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>r</mi> <mi>g</mi> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12711_2025_952_Article_IEq4.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="31" /> </InlineMediaObject> <EquationSource Format="TEX">${r}_{g\times e}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>r</mi> <mrow> <mi>g</mi> <mo>×</mo> <mi>e</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>, EVB achieved the highest phenotypic and genetic gains for BWL and TCL over the 20 generations with SI_TCL50%. However, EVB displayed lower phenotypic means than F1 crosses in the first seven generations due to the loss of heterosis. Additive genetic variances were generally larger in synthetic crosses than in F1 and local animals, explaining the larger responses to selection. In addition, the EVB was the most effective strategy to stabilize inbreeding and retain heterosis in the advanced generations of synthetic animals. Low emphasis on TCL (SI_TCL30%, SI_TCL10%) resulted in negative phenotypic gain for TCL in synthetic animals when rg = − 0.4. In contrast to F1 and rotational crosses, GxE effects did not affect phenotypic gain in synthetic crosses. Conclusions The study demonstrates opportunities for long-term genetic improvement of adaptive and productive performances in smallholder cattle farms using synthetic breeding. Extensive exchange of semen between villages or regions controls inbreeding and additionally contributes to increasing genetic gain. Furthermore, the definition of a suitable selection index prevents antagonistic selection responses caused by negative correlations between traits and GxE effects.

Evaluation of crossbreeding strategies for improved adaptation and productivity in African smallholder cattle farms

期刊论文
出版模式：

开放获取
发表日期：

2025年2月20日

查看全文

Sèyi Fridaïus Ulrich Vanvanhossou,
Tong Yin,
Gregor Gorjanc,
Sven König

摘要

Background

Crossbreeding is successfully implemented worldwide to improve animal productivity and adaptability. However, recurrent failures of crossbreeding programmes in African countries imply the need to design effective strategies for the predominant smallholder production systems.

Methods

A comprehensive simulation procedure mimicked body weight (BW_L) and tick count (TC_L) incidence in a local taurine cattle breed and in an exotic indicine beef cattle breed (BW_E and TC_E, respectively). The two breeds were crossed to produce F1 and rotational animals. Additionally, synthetic breeds were created by applying four schemes defined as farm bull (FB), intra-village bull (IVB), exchanged-village bull (EVB), and population-wide bull (PWB) scheme. These schemes reflect different strategies to select and allocate bulls to smallholder farms. The different crosses were compared with the local breed over 20 generations by varying the genetic correlation between the traits ( ${r}_{g}$ $r_{g}$ = − 0.4, 0, 0.4), genotype-by-environment effects (GxE) between local and exotic environment ( ${r}_{g\times e}$ $r_{g \times e}$ = 0.4, 0.6, 0.8), and the relative emphasis of TC_L compared to BW_L in a selection index (SI_TCL10%, SI_TCL30%, SI_TCL50%).

Results

Regardless of ${r}_{g}$ $r_{g}$ and ${r}_{g\times e}$ $r_{g \times e}$ , EVB achieved the highest phenotypic and genetic gains for BW_L and TC_L over the 20 generations with SI_TCL50%. However, EVB displayed lower phenotypic means than F1 crosses in the first seven generations due to the loss of heterosis. Additive genetic variances were generally larger in synthetic crosses than in F1 and local animals, explaining the larger responses to selection. In addition, the EVB was the most effective strategy to stabilize inbreeding and retain heterosis in the advanced generations of synthetic animals. Low emphasis on TC_L (SI_TCL30%, SI_TCL10%) resulted in negative phenotypic gain for TC_L in synthetic animals when r_g = − 0.4. In contrast to F1 and rotational crosses, GxE effects did not affect phenotypic gain in synthetic crosses.

Conclusions

The study demonstrates opportunities for long-term genetic improvement of adaptive and productive performances in smallholder cattle farms using synthetic breeding. Extensive exchange of semen between villages or regions controls inbreeding and additionally contributes to increasing genetic gain. Furthermore, the definition of a suitable selection index prevents antagonistic selection responses caused by negative correlations between traits and GxE effects.