Variance Components and Sire Evaluation for Milk Flow Rates

Milk flow rates determined by a Milk-o-Meter digital totalizer were observed on 4,023 Holstein-Friesian cows in Ontario and Quebec to estimate components of variance for sire and error for 2-rain yield and its percentage of total milking yield (2-min %) and to predict differences among sires for milk flow rates. Seven percent of the total variation in milk flow rate was from sires. Heritability was .24 for 2-min yield and 2-min %. Sire proofs for 2-rain yield and 2-rain % were on 689 sires used in Ontario and Quebec. Genetic trend in sires for milk flow rates was not apparent. Superior sires for milk flow rates were average sires for milk and fat production but were above average for mammary" system and dairy characteristics. A program for evaluating sires for milk flow rates of their daughters is outlined. --.23 --.65 --1.05 aAdjusted for total milking yield.