Phenotypic and genetic characterization of South African Boran cattle

Abstract

Boran cattle are classified as Zebu and have only been recognized as a breed in South Africa since 1995, with the establishment of the Boran Cattle Breeders’ Society of South Africa on 17 May 2003. Although Boran breeders have been participating in animal recording since 2003 and also joined the BGP (Bovine Genomics Project) in 2016, limited scientific research has been performed on the South African Boran. The aim of this study was to perform a phenotypic and genetic characterisation of the South African Boran based on available data to provide reference data for compiling breeding objectives and further genomic applications. The phenotypic data consisted of pedigree data from 1995 to 2016 and Estimated Breeding Values (EBVs) for seven different traits recorded over the same time period. Pedigree completeness varied from 22.6%, six generations ago with improvement, to 100% in generation one. Furthermore, complete recording for production traits was limited to seven years. This affected the accuracy of the EBVs and could result in incorrect prediction and potential adverse effects on genetic improvement. Maternal birth weight and maternal weaning weight decreased, while birth weight direct and weaning weight direct increased. Yearling weight and final weight increased as well. This indicates that the genetic trends for the previously mentioned production traits were positive except for mature weight. Birth weight remains low which is positive in order to prevent dystocia. Decreased maternal traits can cause cows not being able to raise a calf to weaning due to not sufficient milk produced. Both age at first calving and calving interval also increased over time, resulting in heifers giving birth later in life and longer periods between calving. The genotypic data indicated low inbreeding (-0.027) and revealed high heterozygosity (0.371) for the South African Boran population. Population structure revealed two dominant groups for the Boran. In comparison with other breeds (Bosnmara, Hereford), the Boran was confined as a separate cluster. The Boran breed contributes a well-adapted genetic resource for the beef industry in South Africa. Results confirmed that more attention to breeding objectives and animal recording is required to improve and ensure long-term sustainability.