Herdlife Lactation Yield, Herdlife, and Survival of Holstein and Ayrshire-Based Lines of Dairy Cattle

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Abstract
Length of herdlife, lifetime milk and component yields, daily milk and survival rates were assessed from multiple lactation records of 927 cows in a Holstein line and an Ayrshire-based synthetic line. Holstein cows were progeny of random matings to either Holstein untested sires or progeny-tested Canadian and American Holstein sires. Ayrshire cows were randomly mated to Ayrshire untested sires or Canadian and American Ayrshire, Finnish Ayrshire, Norwegian Red, or Brown Swiss progeny-tested sires to produce the foundation females in the Ayrshire-based synthetic line. The Holstein cattle produced more milk and protein per day of milking herdlife or total herdlife than cows in the Ayrshire-based line and proportionately more survived to initiate second lactations. Daughters of the progeny-tested American and Canadian Holstein sires had significantly higher lifetime and daily milk, protein, and fat yields than daughters of young untested Holstein sires whereas lifetime yields of daughters on untested and progeny-tested Ayrshire sires were equivalent.