Abstract
Genetic breeding programs generally evaluate animals considering the same objectives, but the indices used in the selection criteria can vary. This can give rise to distinct bull rankings in each program. Thus, we aimed to create alternatives for the referral of bulls for mating through multivariate analyses. We used information from the summaries of two genetic evaluation programs (1 and 2) with Nellore bulls. Characteristics were separated into groups: weight, carcass and reproduction. Groups were formed using the mean Euclidean distance and the Tocher optimization method. The means of each trait among the animals allocated to the same group were used to compose the following subindexes: weight gain (siWG), carcass (siCG) and reproduction (siRG). Based on the mean of the group subindex classification, we calculated the average index of group classification (iAGc). When classifying the best groups by characteristics, we observed an increase (superiority of some bulls) in the estimated breeding values (EBVs) by comparison with the total number of bulls evaluated by the programs, selected animals and best 10 final indexes of the programs. There was a change in bull classification when using the iAGc in relation to the classification using the final indexes of the programs. The coefficient of simple coincidence showed that there was a change in bull classification between programs, both between deciles of the final indexes and groups of characteristics. The subindexes siWG, siCG and siRG are important for correcting specific problems in herds. The iAGc should be used instead of the final index of the programs, providing more options for the selection of bulls for mating.
Highlights
In breeding programs, bulls are usually evaluated according to common selection objectives, with variations in the criteria for characteristics and indexesJunior et al Acta Veterinaria Brasilica March 11 (2017) 6-13 distinguish precocious animals without increases in their adult size (MUNIZ et al, 2005; MALHADO et al, 2008).Reproduction traits are fundamental in a selection program
All the estimated breeding values (EBVs) of the characteristics were standardized with mean zero and standard deviation 1 and for the characteristics of birth weight (BW), gestation period (GP), age at first birth (AFB), the signal of the EBVs was inverted by converting them into larger values the better the genetic value for the characteristic
When comparing the means of the EBVs for the characteristics, we observed an increase in the bestrated group (BG) in relation to all the animals evaluated for almost all the characteristics in the two programs (Tables 3 and 4)
Summary
Bulls are usually evaluated according to common selection objectives, with variations in the criteria for characteristics and indexes. Reproduction traits are fundamental in a selection program. Herds with high sexual precocity and fertility have greater availability of individuals for selection or sale, providing greater selection intensity, genetic progress and profitability (GUIMARÃES et al, 2011). According to Brumatti et al (2011), reproduction traits are about 13 times more important than growth traits in determining the economic weights applicable to genetic evaluations. Visual scores and carcass characteristics are interesting to analyzed for animal selection in breeding programs, and should respond rapidly to mass selection (YOKOO et al, 2009). The carcass has great relevance to slaughterhouses to evaluate the value of the purchased product (RESTLE; VAZ; QUADROS, 1999), and the ribeye area correlates with carcass weight and the yield obtained with commercial cuts on the animal’s back (SUGUISAEA et al, 2003)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
