Estimation of genetic parameters for body weights, scrotal circumference, and testicular volume measured at different ages in Nellore cattle

• Grant number: 10/00598-5
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: March 01, 2010
• End date: August 31, 2010
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Genetics and Improvement of Domestic Animals
• Principal Investigator: Lucia Galvão de Albuquerque
• Grantee: Lucia Galvão de Albuquerque
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

Data from 129,575 Nellore cattle bornbetween 1993 and 2006, belonging to the Jacarezinho cattle-raising farm, were used to estimate genetic parameters for scrotal circumference measured at 9 (SC9), 12 (SC12), and 18 (SC18) mo of age and testicularvolume measured at the same ages (TV9, TV12, andTV18) and to determine their correlation with weaning weight (WW) and yearling weight (YW), to provide information for the definition of selection criteria in beef cattle. Estimates of (co)variance components were calculated by the REML method applying an animal model in single- and multiple-trait analysis. The followingheritability estimates and their respective SE were obtained for WW, YW, SC9, SC12, SC18, TV9, TV12, and TV18: 0.33 ± 0.02, 0.37 ± 0.03, 0.29 ± 0.03, 0.39 ± 0.04, 0.42 ± 0.03, 0.19 ± 0.04, 0.26 ± 0.05, and 0.39 ± 0.04, respectively. The genetic correlation between WW and YW was positive and high (0.80 ± 0.04), indicatingthat these traits are mainly determined by thesame genes. Genetic correlations between the growth traits and scrotal circumference measures were positive and of low to moderate magnitude, ranging from 0.23 ± 0.04 to 0.38 ± 0.04. On the other hand, increased genetic associations were estimated between scrotal circumferenceand testicular volume at different ages (0.61± 0.04 to 0.86 ± 0.04). Selection for greater scrotal circumference in males should result in greater WW, YW, and testicular volume. In conclusion, in view of the difficulty in measuring testicular volume, there isno need to change the selection criterion from scrotal circumference to testicular volume in genetic breeding programs of Zebu breeds. (AU)