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1 Department of Animal Science, Michigan State University, East Lansing 48824-1225
Blood samples from 262 lactating Holstein cows were analyzed to determine the glutathione concentration in erythrocytes. Concentration data were fitted by an animal model that contained stage of lactation, herd, parity, and season as fixed effects; milk yield as a covariate; and 520 animal effects.
A derivate-free algorithm of the REML procedure was applied for estimation and prediction. Heritability estimates were .61 ± .16 for the ratio of glutathione concentration to red blood cell count and .67 ± .17 for glutathione concentration in whole blood. After the 35 cows with breeding values >.50 were excluded from the data, heritability estimates reduced to .03 ± .19 and .19 ± .19, respectively. These 35 cows were progeny of 19 sires that showed an intrasire bimodal distribution of the erythrocyte glutathione concentrations. These results suggested a single gene diallele polymorphism in erythrocyte glutathione in Holstein cows, as found in other ruminant species.
No evidence indicated association between glutathione concentrations and 305-d milk yield, protein yield, fat yield, or fat percentage. However, glutathione concentration in whole blood explained an additional 2.3% of total variation in protein percentage. Protein percentage and glutathione concentration were related positively phenotypically, but genetic correlations between protein percentage, protein yield, and blood values were significantly negative.
Key Words: erythrocyte glutathione milk yield single gene effect
Submitted on May 18, 1992
Accepted on October 13, 1992
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