Genetic and Nongenetic Effects on Erythrocyte Osmotic Fragility in Lactating Holstein Cows and Its Association with Yield Traits

¹ Department of Animal Science, Michigan State University, East Lansing 48824-1225

Blood samples from 262 lactating Holstein cows were analyzed to determine the resistance of erythrocytes to hypotonic NaCl solutions. The animal model contained stage of lactation, herd, parity, and season as fixed effects, milk yield as a covariate, and 520 random animal effects.

A derivate-free algorithm of REML procedure was applied for estimation and prediction. The results suggested higher hemolysis rates and mean corpuscular fragility in first than in later lactations and decreased erythrocyte fragility in cows in late lactation. A negative linear regression of percentage of hemolysis on weekly milk yield was significant. Heritability estimates were .58 ± .14 for hemolysis rate at 111 mM NaCl and .47 ± .18 for mean corpuscular fragility. Estimates for hemolysis rates decreased with increasing osmotic fragility at lower NaCl concentrations. Phenotypic correlations between erythrocyte fragility traits and 305-d milk, fat, and protein yields were all negative and low. Moderately negative genetic correlations between red blood cell osmotic fragility and fat yield and fat percentage and slightly positive genetic correlations between red blood cell osmotic fragility and protein yield and protein percentage suggested possible alterations in erythrocyte membrane stability if milk component traits were targets for genetic selection.

Key Words: erythrocyte osmotic fragility • milk component • heritability • genetic correlation

Submitted on July 23, 1992
Accepted on February 16, 1993