Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2017
Publication Date: 1/29/2018
Citation: Hay, E.A., Roberts, A.J. 2018. Genotype x prenatal and post-weaning nutritional environment interaction in a composite beef cattle breed using reaction norms and multi-trait model. Journal of Animal Science. 96:444-453. https://doi.org/10.1093/jas/skx057.
Interpretive Summary: Several economically important traits in beef cattle are often under the control of genetic, environmental factors and their interaction. The genetic merit and response to selection of animals differs according to the environment and management in which they are evaluated. This key factor has been ignored by national cattle evaluation systems, it is crucial that genetic sensitivity is taken into consideration in the selection and improvement of beef cattle. This study evaluates the extent of genetic by nutritional environment interaction on growth and carcass traits in composite beef cattle breed using multi-trait and reaction norms models.
Technical Abstract: Environmental effects have been shown to influence several economically important traits in beef cattle. In this study, genetic x nutritional environment interaction has been evaluated in a composite beef cattle breed (50% Red Angus, 25% Charolais, 25% Tarentaise). Four nutritional environments (MARG-RES, MARG-CTRL, ADEQ-RES and ADEQ-CTRL) were created based on 2 levels of winter supplement provided to dams grazing winter range during gestation (MARG and ADEQ) and 2 levels of input to offspring during post-weaning development (RES and CTRL). Genetic parameters of average daily gain during the 140-d post wean trial (ADG), yearling weight (YW), and ultrasound measurement of fat depth over the rib (FAT) and intramuscular fat (IMF) of 3,020 individuals in the four environments were estimated. The heritabilities estimated using a single trait mixed linear model were: ADG: 0.21, 0.23, 0.19 and 0.21; YW: 0.27, 0.33, 0.20 and 0.26; FAT: 0.30, 0.29, 0.29, 0.55; IMF: 0.45, 0.51, 0.33, 0.53 for MARG-RES, MARG-CTRL and ADEQ-RES and ADEQ-CTRL respectively. To evaluate the extent of genotype x environment interaction reaction norms and multi-trait models were implemented. The genetic correlations estimated using a multi-trait model for ADG, YW, FAT and IMF. Growth traits (ADG, YW) and FAT showed correlations less than 0.80 threshold across the four different environments indicating genetic by environment interaction. For example, genetic correlation for ADG between MARG-CTRL and MARG-RES was 0.73 and 0.65 between ADEQ-RES and MARG-RES. In this example, the former genetic correlation corresponds to differences in post-weaning nutritional environment, and the later represents a nutritional difference imposed on dams (i.e., prenatal environment), potentially mediated via fetal programming. The reaction norm model results were in concordance with the multi-trait model, genotype by environment interaction had a higher effect on traits with a lower heritability.