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Inheritance of Lactation Curve in Swiss Brown Cattle

Institute of Animal Production, Swiss Federal Institute of Technology, Zurich, Switzerland

ABSTRACT

Lactation curves for milk and fat yield were estimated for 159,541 Swiss Brown cows by two models:

In these y₁ and t₁ are yield and day in lactation at the i^th milk recording. The b and B are associated with the increase, c and C with the decrease of production, a and A are constants associated with production, and t_o indicates the time of the initial production. Model [2] gave smaller mean squared errors than Model [1] and less curves with negative estimates for B or C than for b or c in Model [1]. Heritabilities for measures of persistency ranged from .19 to .29. The C was not correlated genetically with 305-day yield and was positively correlated with 100-day yield. Genetic correlations between persistency and 305-day yield were .05 to .16 and between persistency and 100-day yield –.23 to –.35. This indicates that breeding for 100-day yield would decrease persistency, while breeding for 305-day yield would not affect it adversely.

This article has been cited by other articles:

				O. Martin and D. Sauvant Metaanalysis of Input/Output Kinetics in Lactating Dairy Cows J Dairy Sci, December 1, 2002; 85(12): 3363 - 3381. [Abstract] [Full Text] [PDF]