Genetic models for breed quality and navel development scores and its associations with growth traits in beef cattle

Abstract

Estimation and prediction ability of linear and threshold models for yearling breed quality score (BQ) and navel development score at weaning (WN) and yearling (YN), considering variances, heritabilities, and rank correlations based on the breeding values predicted for bulls, were compared. Furthermore, it was determined whether BQ, WN, and YN are genetically associated with growth traits (BWG: birth to weaning weight gain, WH: weaning height, WYG: weaning to yearling weight gain, YH: yearling height) to field data of Nelore cattle. For BQ, similar heritabilities were estimated using linear (0.14 ± 0.01) and threshold (0.15 ± 0.02) models. For navel development scores, higher heritability was estimated with threshold (WN 0.22 ± 0.03; YN 0.42 ± 0.03) rather than linear (WN 0.16 ± 0.01; YN 0.29 ± 0.01) models. Rank correlations between sires breeding values predicted for visual scores with linear and threshold models ranging from 0.53 to 0.98, indicating that different sires would be selected using these models, mainly for higher selection intensities. The BQ showed little genetic variability and was not associated with WH and YH. However, low and positive genetic correlations were obtained between BQ with BWG (0.27 ± 0.02) and WYG (0.25 ± 0.02). In general, they are expected low genetic gains for BQ as correlated response to selection based on any of the growth traits studied. The WN showed higher genetic correlation with BWG (0.63 ± 0.02) and WH (0.53 ± 0.02) rather than WYG (-0.06 ± 0.02) and YH (0.26 ± 0.02), indicating that selection for increased growth at weaning (height and weight gain) should lead to longer and most pendulous navels at this age. Weak genetic correlations were obtained between yearling navel and growth traits.

Genetic analysis of growth, visual scores, height, and carcass traits in Nelore cattle

“…For young Nelore bulls on pasture performance test stations, Lima et al (2013) found a slightly lower heritability for racial traits. Similarly, Boligon et al (2016) obtained a heritability of 0.15 for BQ score using part of the same population included in the present study. However, Faria et al (2009) and Reimann et al (2018) reported heritability of 0.21 and 0.32, respectively, for visual score of racial traits at yearling in Nelore and taurine breeds.…”

“…On the other hand, Lima et al (2013) reported moderate genetic correlations between navel score and growth traits (0.28-0.44). Additionally, Boligon et al (2016) estimated genetic associations of 0.210 and À0.002 between navel score at yearling and weight gain from birth to weaning and from weaning to yearling, respectively.…”

“…Some visual assessment methods of Zebu breeds also attribute navel and breed quality (BQ) scores. The size and shape of the navel are important traits, especially for animals raised on pastures with shrubs because males with pendulous navels are more susceptible to injuries, reducing their use or making them unsuitable for breeding (Bignardi et al , 2011; Holroyd & McGowan, 2014; Boligon et al , 2016; Abreu, Mota et al, 2018; Romero et al, 2018). In contrast, all items observed in the breed standard are included in the BQ score, which is a negotiation tool in the market, particularly in elite herds (Faria et al , 2009; Boligon et al , 2016; Abreu, Mota et al, 2018).…”

Population differentiated copy number variation of Bos taurus, Bos indicus and their African hybrids

“…A pendulous navel increases risk of injuries and infection caused by friction against pasture [ 30 ]. During natural mating, bulls with long and pendulous navels are frequently exposed to injuries and trauma [ 31 ]. Expression of HMGA2 gene is also responsible for body size by regulating myoblast proliferation and myogenesis.…”

Association of Copy Number Variation at Intron 3 of HMGA2 With Navel Length in Bos indicus

“…Navel length at yearling (NY) is an economically important trait in beef cattle raised in extensive production systems. A pendulous navel increases the risk of injuries caused by friction against the pasture, leading to infection, reproductive impairment and treatment expenses (Ashdown, 2006; Rabelo et al, 2008; Boligon et al, 2016). This trait is especially important to cattle raised in Brazil, the second largest beef exporter of the world, where Nellore ( Bos indicus ) animals compose the majority of the herds and approximately 88% of the females in reproductive age are subjected to natural mating (Asbia, 2016).…”