Effects of management intensity and genetic value of the sire on milk yield and form of lactation curve of first-lactation Simmental cows

Breeding goal for Simmental cattle actually focuses on intensively managed dairy farms. Under continued selection for milk yield dairy farmers frequently raise the question whether the use of bulls with high breeding values for milk yield on extensive dairy farms is appropriate. Therefore the present investigation analysed the effect of breeding value for milk yield on first lactation yield and on the shape of lactation curve on farms with different intensity of management. Data comprised 278 bulls of birth years 1993 to 1994 and their daughters (327.509 cows) in Bavaria. Daughters were divided into 3 groups with respect to relative breeding value for milk yield of their sire and to intensity of management. Milk, fat and protein yield and lactation curves were compared between groups and intensities. As could be expected, the advantage in milk, fat and protein yield of daughters of high yielding bulls is significantly higher under intensive conditions. Under intensive management, lactation curves of daughters of high yielding sires showed a steep slope up to lactation peak. Peak milk yield was higher and day of peak milk yield was later in lactation. Under extensive conditions lactation curves were much flatter, indicating better persistency. The hypothesis that daughters from high yielding bulls under extensive conditions will start high into lactation followed by a drastic collapse in milk yield due to metabolic stress was not confirmed.

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