Comparison of selection criteria for sexual precocity and their association with growth traits in Nellore cattle

Revista Brasileira de Zootecnia

Fries, Luiz Alberto²  Queiroz, Sandra Aidar de²  Ortiz Peña, Carlos Dario¹ 

[1] UNESP, Jaboticabal

关键词: average daily gain;    days to gain 160 kg from birth to weaning;    genetic correlation;    heritability;    rank correlation;    scrotal circumference corrected to age and live weight   IntroduçãoO perímetro escrotal (PE) é;    em animais jovens;    indicador útil do tamanho testicular;    da capacidade de produção espermática;    das características físicas do sêmen;    da idade à puberdade e;    também;    da fertilidade dos machos e das fêmeas aparentadas (meio-irmãs e filhas) (COULTER e KELLER;    1982;    TOELLE e ROBINSON;    1985;    ALENCAR et al;   

DOI  :  10.1590/S1516-35982001000100015

学科分类：兽医学

来源: Universidade Federal de Vicosa

【 摘 要 】

- In this study genetic parameters of scrotal circumference (SC), SC corrected for age (SC/a) and SC/a corrected for live weight (SC/aw) of Nellore Cattle were estimated and comparisons of the rank based on EPDs of the above criteria were made. In addition, the genetic correlations between SC measurements and growth (preweaning average daily gain, number of days to gain 160 kg after birth, post weaning average daily gain and number of days to gain 240 kg after weaning) were estimated. The information came from the Paraguayan Nellore Breeders Association Production Registry, obtained from 1986 to 1997, in 110 herds. Restricted Maximum Likelihood using one-trait animal models were used to obtain the variance components and heritability estimates. The heritability estimates were 0.41, 0.40, and 0.47 for SC, SC/a and SC/aw, respectively, all of them indicating the possibility of genetic improvement by selection. The estimate of genetic correlation between SC/a and SC/aw (0.62) was moderate and the obtained values for the correlations between the sexual precocity and growth traits were of small magnitude. The rank correlations between EPDs estimates were 0.98 for SC and SC/a and 0.59 for SC/a and SC/aw. The results showed changes in the classification of animals selected when live weight was or was not considered in the SC correction. The selection criterion scrotal circumference corrected for age and live weight (SC/aw) could reduce a correlated response with larger adult size, while obtaining substantial improvement in sexual precocity.

【 授权许可】

CC BY-NC