Sources of bias, genetic trend and changes in genetic correlation in carcass and ultrasound traits in the icelandic sheep population

Abstract

Genetic parameters for carcass conformation, carcass fat, ultrasound eye muscle depth and ultrasound fat depth over eye muscle were estimated with data from Icelandic farms during three periods, 2001-2003, 2006-2008 and 2011-2013. Heritability ranged from 0.30 to 0.42. Genetic correlation between carcass conformation and carcass fat was 0.41, 0.29 and 0.26 in 2001-2003, 2006-2008 and 2011-2013, respectively.Breeding values based on carcass scoring records of 5,796,474 lambs in 2000-2013 were estimated with a bivariate model and compared to the results of a multitrait model, including 715,771 ultrasound records. The genetic merit of rams for carcass conformation was underestimated in the bivariate analysis in the cases where many offspring were kept for replacement. Applying the multitrait model reduced this bias and gave more accurate results for both traits.The genetic trend was -0.05 and 0.08 genetic standard deviations per year for carcass fat and carcass conformation, respectively, in the period 2000-2013.

Genome-Wide Association Analyses Highlight the Potential for Different Genetic Mechanisms for Litter Size Among Sheep Breeds

“…Hu sheep is famous for early sexual maturity and high fecundity, and are distributed in the Taihu Lake area of Eastern China ( Yue, 1996 ). Icelandic and Finnsheep (Finnish Landrace) sheep are northern European high-fecundity breeds ( Mullen and Hanrahan, 2014 ; Eiriksson and Sigurdsson, 2017 ). Romanov sheep from the Volga Valley shows outstanding reproduction qualities: early sexual maturity, out-of-season breeding and extraordinary prolificacy ( Deniskova et al, 2017 ).…”

A Comparison of Two Different Slaughter Systems for Lambs. Effects on Carcass Characteristics, Technological Meat Quality and Sensory Attributes

“…2 Standard error of the mean. 3 Differences considered significant at p < 0.05 and tending towards significance at 0.05 < p ≤ 0.10. a,b = Mean values within rows with different superscripts differ significantly. 4 Difference between hot and cold carcass weight (%).…”

“…However, a more recent study indicated a decrease in tenderness of Musculus longissimus dorsi meat from Icelandic lamb during the past two decades [2]. Probable reasons for this trend are (i) ongoing breeding for increased muscle and decreased fat using progeny testing, based on ultrasound measurements of live animals for animal selection [3], and (ii) changes in slaughter practices, with faster chilling of lamb carcasses and low-voltage electrical stimulation. It is known that rapid chilling of carcasses can affect meat tenderness negatively, by increasing the risk of cold shortening [4].…”

The value of incorporating carcass trait phenotypes in terminal sire selection indexes to improve carcass weight and quality of heavy lambs

“…Consequently, the general objective of most terminal sire sheep breeding programmes is to increase the lean meat production of carcasses (Anderson, Pethick, & Gardner, 2016; Tosh & Wilton, 2002). In recent years, substantial genetic progress for these traits has been made in countries such as Australia (Swan, Banks, Brown, & Chandler, 2017; Swan, Brown, & Banks, 2009; Swan, Pleasants, & Pethick, 2015), New Zealand (Newman, McEwan, & Young, 2009; Sheep Improvement Limited, 2018; Young & Amer, 2009), the United Kingdom (Amer et al, 2007, 2015), Iceland (Eiriksson & Sigurdsson, 2017) and Canada (GenOvis, 2016). Nevertheless, genetic improvement programmes are continually evolving to address industry challenges by refining breeding objectives and incorporating novel traits.…”