Long-term selection experiment with Afrikaner cattle 1. Environmental factors affecting calf growth traits

2009 ◽  
Vol 39 (2) ◽  
Author(s):  
JB Van Wyk ◽  
LM Beffa ◽  
GJ Erasmus
Keyword(s):  
Environmental Factors ◽  
Growth Traits ◽  
Selection Experiment ◽  
Factors Affecting ◽  
Calf Growth ◽  
Term Selection

Species Responses to Grazing and Environmental-Factors in an Arid Halophytic Shrubland Community

1987 ◽  
Vol 35 (2) ◽  
pp. 135 ◽  
Author(s):  
RB Hacker
Keyword(s):  
Environmental Factors ◽  
Soil Salinity ◽  
Large Scale ◽  
Chemical Properties ◽  
Grazing Pressure ◽  
Aerial Photographs ◽  
Small Scale ◽  
Factors Affecting ◽  
Species Responses

Species responses to grazing and environmental factors were studied in an arid halophytic shrubland community in Western Australia. The grazing responses of major shrub species were defined by using reciprocal averaging ordination of botanical data, interpreted in conjunction with a similar ordination of soil chemical properties and measures of soil erosion derived from large-scale aerial photographs. An apparent small-scale interaction between grazing and soil salinity was also defined. Long-term grazing pressure is apparently reduced on localised areas of high salinity. Environmental factors affecting species distribution are complex and appear to include soil salinity, soil cationic balance, geomorphological variation and the influence of cryptogamic crusts on seedling establishment.

Kyphoscoliosis in a Long-Term Selection Experiment with Chickens

1971 ◽  
Vol 15 (2) ◽  
pp. 376 ◽  
Author(s):  
Lewis W. Taylor
Keyword(s):  
Selection Experiment ◽  
Term Selection

scholarly journals Identification of Genes Targeted in South African Merino and Afrino Sheep Populations Under Long-Term Selection for Reproduction and Body Weight

2020 ◽  
Author(s):  
Margaretha Snyman ◽  
Sunika Süllwald ◽  
Willem Olivier ◽  
Carina Visser
Keyword(s):  
Body Weight ◽  
South African ◽  
Reproductive Performance ◽  
Genome Wide Association Study ◽  
Growth Traits ◽  
Reproductive Traits ◽  
Term Selection ◽  
A Genome ◽  
Selection For

Abstract Background: Reproductive performance and body weight are of the utmost economic importance in determining the efficiency of sheep production. Simultaneous selection for increased reproductive performance and early growth traits is a common strategy in many flocks, but ambiguous results regarding the relationship between reproduction and body weight have been reported. The objective of this study was to perform a genome-wide association study (GWAS) in two South African Merino flocks and an Afrino sheep flock that were selected for both reproduction and body weight over decades. The GWAS aimed to identify SNPs associated with genes affecting the traits number of lambs born (NLB), number of lambs weaned (NLW), total weight of lamb weaned (TWW) and body weight (BW) and thus to ascertain which genes were targeted through directional selection.Results: In the GWAS, 16 SNP markers associated with reproductive traits were identified among the three populations, while 15 SNPs were associated with body weight. These SNPs were linked respectively to 26 and 21 documented genes in the sheep genome. Most of these genes were previously associated in literature with reproduction related, as well as with growth related traits in various farm animal species. This study, supported by results from previous studies performed on sheep and cattle, identified the following genes that warrant further investigation as to their functions and processes relating to growth and reproduction in sheep: MAP7D1, TRAPPC3, THRAP3, TRMP8, SPP2, HDAC9, ZFHX3, SIX6, C14orf39, TAF4B, TRSP1 EYA2, RBMS3, STL38L, BSPH1, LIG1, CABP5 and ELSPBP1. Conclusions: Long-term selection in the flocks for both body weight and reproductive traits, and especially on the composite trait TWW, have favoured genes with pleiotropic effects influencing both groups of traits. SNPs associated with these pleiotropic genes were detected in the association analyses for the various traits.

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