Validation of a beef cattle maternal breeding objective based on a cross-sectional analysis of a large national cattle database

Abstract

Despite the importance of validating any technology prior to recommendation for use, few studies exist in the scientific literature that have demonstrated the superior performance of high-ranking animals in a given total merit index; this is especially true for maternal cattle selection indexes. The objective of the present study was to demonstrate the impact of the Irish total merit maternal-based index and provide the benefits of using the Irish total merit maternal-based beef index as part of a breeding policy. The validation exercise was undertaken using 269,407 records (which included the cow’s own records and her progeny records) from 92,300 females differing in a total merit index for maternal value; a comparison was also made with the Irish terminal index. Association analyses were undertaken within the framework of linear and threshold mixed models; the traits analyzed were fertility (e.g., calving interval), slaughter (e.g., harvest weight), live-weight (e.g., weaning weight) and producer-recorded traits (e.g., docility). All traits were analyzed with the maternal index and terminal index fitted as covariate(s) separately. Depending on the independent variable analyzed, the other fixed effects included: parity of cow, heterosis and recombination loss of cow and/or progeny, gender of progeny and the EBV of the sire; contemporary group was included as a random effect. The results demonstrate the effectiveness of using total merit indexes to improve performance in a whole range of different traits, despite the often antagonistic genetic correlations among traits that underpin the index. Cows excelling on the maternal index had less calving difficulty, superior fertility performance, lighter carcasses and live-weight, as well as being more easily managed. Additionally, progeny of higher maternal index cows were lighter at birth and more docile albeit with a small impact on slaughter traits. In contrast, higher terminal index cows had more calving difficulty, compromised fertility and had heavier carcasses themselves as well as their progeny. While the differences in phenotypic performance between groups on maternal index was, in most instances, relatively small, the benefits are: a) expected to be greater when more genetically extreme groups of animals are evaluated and b) expected to accumulate over time given the cumulative and permanent properties of breeding schemes.

Cross-sectional analyses of a national database to determine if superior genetic merit translates to superior dairy cow performance

“…Validating the suite of traits encompassing such breeding goals is fundamental to the successful adoption and extension of such tools, as well as identification of deviations from expectation that may trigger methodological improvements. Many studies have reported progressive genetic trends in cattle, both at the level of individual trait EBV (García-Ruiz et al, 2016;Berry, 2018;Ring et al, 2019) and at the level of the overall breeding goal (Wiggans et al, 2017;Twomey et al, 2020a); nonetheless, few studies in dairy cattle (Ramsbottom et al, 2012;Newton et al, 2017;Berry and Ring, 2020;Fessenden et al, 2020) have validated that such genetic progress translates to phenotypic improvements on-farm. The present study provides a realistic representation of the phenotypic response achievable in the average environment at a given level of genetic merit for all traits in the Irish total merit index.…”

“…Ideally, a 1-unit change in EBV should translate to an equivalent 1-unit change in observed animal performance in the average environment; many studies in cattle have validated such hypotheses both when genetic divergence was defined at the individual trait level (Twomey et al, 2016;Ring et al, 2019;Judge et al, 2019) or at the overall breeding goal level (Connolly et al, 2016;Newton et al, 2017;Berry and Ring, 2020;Fessenden et al, 2020;Twomey et al, 2020a). Based on a controlled validation study of 272 Irish Holstein-Friesian cows, O' Sullivan et al (2019) documented a regression coefficient between milk yield, fat yield, and protein yield per unit change in their respective trait PTA (i.e., half the EBV) of 1.66 kg (95% CI: 1.17, 2.14), 1.47 kg (95% CI: 0.96, 1.98), and 1.11 kg (95% CI: 0.52, 1.71), respectively; the expected coefficient was 2 kg.…”

Sensory Consumer and Descriptive Analysis of Steaks from Beef Animals Selected from Tough and Tender Animal Genotypes: Genetic Meat Quality Traits Can Be Detected by Consumers

“…Breeding has a particular advantage of being sustainable, rapid, cumulative and permanent. Several breeding goals exist in the dairy [37], beef [31,38] and beef-on-dairy industries [39]. These breeding goals are comprised of many traits thought to influence profit, thus providing a proven [32,38,40] vehicle to achieving genetic gain in a number of traits simultaneously, even if antagonistically correlated.…”

“…Several breeding goals exist in the dairy [37], beef [31,38] and beef-on-dairy industries [39]. These breeding goals are comprised of many traits thought to influence profit, thus providing a proven [32,38,40] vehicle to achieving genetic gain in a number of traits simultaneously, even if antagonistically correlated. Inclusion of meat sensory traits in such breeding goals is crucial to achieve generation-on-generation gains in these metrics.…”

The development of effective ruminant breeding programmes in Ireland from science to practice

“…Breeding is not exempt from such demands. Ireland is, by far, the most prolific in studies investigating the relationship between genetic merit and subsequent phenotypic performance; this is true of dairy cattle (Ramsbottom et al, 2015;O'Sullivan et al, 2019;Ring et al, 2021), beef (Clarke et al, 1999;McHugh et al, 2014;Connolly et al, 2019;Twomey et al, 2020) and sheep (McHugh et al, 2017(McHugh et al, , 2020.…”