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Title: MATERNAL LINE EFFECT IN PRODUCTIVE TRAITS IN MEXICAN SIMMENTAL-SIMBRAH POPULATION

Author
item ROSALES- ALDAY, J. - CIRNE-INIFAP, CE ALDAMA
item OLSON, T. - UNIVERSITY OF FLORIDA
item Riley, David
item MONTANO B., M. - CENID FISIOLOGIA

Submitted to: J Tecnica Pecuaria En Mexico
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2004
Publication Date: N/A
Citation: N/A

Interpretive Summary: Most cattle production traits are influenced solely by genetic material within the nucleus of cells; however, there is a small quantity of genetic material in cells that is not in the cell nucleus, but in structures that are in the cell cytoplasm. This 'cytoplasmic' genetic material is transmitted from parent to offspring solely through maternal inheritance in most organisms, including cattle, and is known to be influential on growth and energy usage in mammals. The objectives of this study were to estimate the amount of genetic control (including individual and maternal) as well as the influence of the cytoplasmic genetic component on birth weight and 205 day weight in Simmental and Simbrah cattle. Analyses of birth weight records from the Mexican Simmental-Simbrah Association showed that 39% of birth weight variation was due to genetic material of the animal itself, 4% was due to the genetic material of the dams, and 2% was due to the cytoplasmic genetic material described above. Separate analyses showed that 31, 5, and 3% of the total variation in calf 205 day weight was due to individual, maternal, and cytoplasmic genetic effects. Simultaneous estimation of cytoplasmic effects in cattle evaluations may result in more accurate estimates of genetic control of these traits. Accurate estimates improve the ability to rank bulls accurately and facilitate selection decisions according to their ability to sire progeny with lower birth weights and/or higher weaning weights.

Technical Abstract: Purebred Simmental and crossbred Simmental-Zebu records from the Mexican Simmental-Simbrah Association were used to estimate variance components for additive direct, maternal and cytoplasmic line genetic effects on birth and weaning weight traits. Three data sets were formed: purebred Simmental and crossbred; only purebred and only crossbred animals. Variances were estimated by Restricted Maximum Likelihood procedures using a Sire-Maternal Grand Sire model. Fixed effects were sex, age of dam linear and quadratic, contemporary groups and calf-sex x age of dam interaction. Heritabilities for both purebred and crossbred animals were 0.39 +/- 0.03, 0.04±0.01 for birth weight direct and maternal, respectively. The genetic correlation between birth weight direct and maternal was 0.30 +/- 0.08 and for maternal and cytoplasmic effects was 0.52 +/- 0.43. Heritabilities for 205-d weight direct and maternal effects were 0.27 +/- 0.04 and 0.05 +/- 0.009. Heritabilities for Simmental purebred data for birth weight direct and maternal were 0.25 +/- 0.08 and 0.04 +/- 0.02. Heritabilities for 205-d weight direct and maternal effects were 0.36 +/- 0.13 and 0.017 +/- 0.023. Heritabilities for crossbred animals were 0.44 +/- 0.03 and 0.03 +/- 0.01 for birth weight direct and maternal. The genetic correlation between birth weight direct and maternal was 0.36 +/- 0.08 and for maternal and cytoplasmic effects was 0.27 +/- 0.21. Heritabilities for 205-d weight direct and maternal effects were 0.31 +/- 0.05 and 0.05 +/- 0.01. Cytoplasmic line variance and total phenotypic ratio ranged from 2 to 3% for all traits in all data groups. Modest contributions of the cytoplasmic mitochondrial effect to birth and weaning weight variation were found in this study.