Effects of the F94L Limousin associated myostatin gene marker on metabolic index in growing beef heifers

Authors: Hales Paxton, Kristin; Tait Jr, Richard; Lindholm-Perry, Amanda; Cushman, Robert - Bob; Freetly, Harvey; Brown-Brandl, Tami; Bennett, Gary

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2020
Publication Date: 12/1/2020
Publication URL: https://handle.nal.usda.gov/10113/7198244
Citation: Hales, K.E., Tait Jr, R.G., Lindholm-Perry, A.K., Cushman, R.A., Freetly, H.C., Brown-Brandl, T.M., Bennett, G.L. 2020. Effects of the F94L Limousin associated myostatin gene marker on metabolic index in growing beef heifers. Applied Animal Science. 36(6):851-856. https://doi.org/10.15232/aas.2020-02046.
DOI: https://doi.org/10.15232/aas.2020-02046

Interpretive Summary: The U.S. Meat Animal Research Center (USMARC) has a unique population of cattle that contain an allele for the myostatin gene, which influences protein accretion. The heifers used in this study were genotyped for this gene and we used either homozygous wild type heifers, or heifers that had 2 copies of the myostatin gene. Body weight was not different between treatments, but it did differ across day increasing as the heifer’s age increased. Oxygen consumed (as an indicator of metabolic rate) was greater for the wild type heifers than the heifers with the myostatin gene, on all days measured. Heat production decreased as heifer age increased in all heifers irrespective of treatment. Respiratory quotient had a tendency to be greater for heifers with the myostatin gene than wild type heifers. Average daily gain measured across the whole study (121 d) was greater for heifers with the myostatin gene. In conclusion, oxygen consumption and heat production were less for heifers with the myostatin gene, while the respiratory quotient tended to be greater. Therefore, it is likely that cattle with the myostatin gene have lower maintenance energy requirements than cattle without the gene. Thus, genotype, if known, should be considered when assessing energy requirements of beef cattle.

Technical Abstract: Objective: Our objective was to evaluate fasting heat production in cattle with and without the GDF8 mutation. Materials and Methods: The heifers used in this study were genotyped for the myostatin (MSTN) gene mutation to determine their MSTN genotype as either homozygous normal for phenylalanine at amino acid position 94 of MSTN (0 copy; n = 5) or homozygous for F94L variant in MSTN (2 copy; n = 6). Oxygen consumption was measured using portable headbox respiration calorimeters, and heat production was calculated. Results and Discussion: Body weight was not different between treatments (P = 0.33), but it did differ across days (P < 0.01), increasing as heifer age increased. Oxygen consumed in liters per kilogram of metabolic BW was greater for 0 copy heifers than the heifers with 2 copies of the F94L MSTN variant (P = 0.03), on all days measured. Oxygen consumed and heat production decreased as heifer age increased in all heifers irrespective of genotype (P = 0.03). Respiratory quotient had a tendency to be greater for heifers with 2 copies than for heifers with no copy (P = 0.07). Average daily gain measured across the whole study (121 d) was greater for heifers with 2 copies of the F94L MSTN variant. Implications and Applications: Therefore, it is likely that cattle with 2 copies of the F94L MSTN substitution have lower maintenance energy requirements than cattle without the MSTN gene. Thus, genotype, if known, should be considered when assessing energy requirements of beef cattle.