Selection for higher body weight in Nelore cattle is effective in achieving an increase of longissimus muscle area without reducing subcutaneous fat thickness

Abstract

-The objectives of this study were to estimate heritabilities and genetic and phenotypic correlations between carcass traits measured by ultrasound and other economically important traits generally used as selection criteria in beef cattle and to estimate the genetic changes in the carcass traits as a result of selection for post-yearling weight. Carcass traits measured by ultrasound at two ages (12 and 18 months) and the correlation of these traits with weight, hip height and body condition score of males (yearling) and females (post-yearling) were analyzed. Multi-trait analysis was performed using the restricted maximum likelihood method under an animal model. To demonstrate the effect of selection for growth, phenotypic and expected breeding value means of the carcass traits and weights according to selection line (Nellore control line, selection line and traditional line) were estimated using records from animals born in the last 3 years (2006 to 2008). The heritability estimates were high for longissimus muscle area (LMA) at 12 and 18 months of age (0.47 and 0.40, respectively). For fat thickness measures, heritabilities ranged from 0.37 to 0.29. Genetic correlations of the same trait between the two ages were high for LMA (0.95). The Nellore breed shows medium to high genetic variability in carcass traits measured by ultrasound at 12 and 18 months of age, and a greater response is expected if selection for backfat thickness is performed at about 12 months of age. Selection for higher body weight will lead to an increase of LMA at the two ages without reducing subcutaneous fat thickness.

Ranking of Nellore animals in cattle championships: genetic parameters and correlations with production traits

“…Table 3 shows the results of descriptive statistics for variance and heritability estimates of growth, fertility, and carcass traits obtained by two-trait analysis with TOP5. For some traits, heritability estimates were higher than those reported for Nellore herds, whereas heritability for HH was similar (Cyrillo et al, 2001;Magnabosco et al, 2002;Giannotti et al, 2005;Yokoo et al, 2010;Pinheiro et al, 2012). However, heritability for BW was much higher than estimates reported in previous studies.…”

“…This may be beneficial because these traits show a favorable genetic and phenotypic correlation with carcass weight (Bonilha et al, 2008). However, genetic gain in HH, which is also genetically correlated with TOP3 and TOP5, may be undesirable as there is evidence of a negative, but relatively low, genetic correlation between HH and carcass traits of finishing cattle (Yokoo et al, 2010;Pinheiro et al, 2012). The medium genetic correlation between SC and TOP3 (0.439 ± 0.072) and TOP5 (0.382 ± 0.067) may be improved through the use of high-ranked animals as bulls.…”

“…Because of its favorable genetic correlation with semen quantity and quality (Silva et al, 2011), heifer sexual precocity (Eler et al, 2004), and its medium heritability (0.42), SC should be an important trait for judging bulls at cattle championships. Genetic variation in BF and RF has been reported for Nellore cattle (Yokoo et al, 2008;Pinheiro et al, 2012), which may be explored for selection. Furthermore, these traits are important for the commercialization of bovine carcasses and should also be considered when judging cattle at championships.…”

“…Genetic parameters for postweaning growth traits of Zebu beef cattle have been reported in many studies (Giannotti et al, 2005), whereas studies investigating genetic parameters for traits related to body measures and ultrasound-measured carcass traits are limited (Cyrillo et al, 2001;Magnabosco et al, 2002;Riley et al, 2007;Yokoo et al, 2008;Pinheiro et al, 2012). Moreover, there have been no studies to examine the genetic parameters of traits related to cattle ranking in championships and the genetic and phenotypic correlations of these traits with production traits, such as body weight at certain ages, scrotal circumference, rib eye area, or fat thickness.…”

Growth curves of carcass traits obtained by ultrasonography in three lines of Nellore cattle selected for body weight

“…Altarriba et al (2005) evaluated the effect of selection for weight at 210 days of age on carcass traits in Pirenaica animals, which resulted in a greater REA. Pinheiro et al (2012) studied the same lines as used here and reported an increase in the genetic merit of selected Nellore animals (NeS and NeT), with an annual genetic gain of 0.14 and 0.12 cm 2 in REA at 12 and 18 months of age, respectively. Soutello et al (2002) evaluated the development of loin eye area and subcutaneous fat thickness in young bulls (Nellore, ½ Angus-Nellore, ½ Simmental-Nellore, and Canchim) raised in a feedlot system, and reported significant differences in REA at the beginning of the feedlot period between the genetic groups.…”