After the January 2009 USDA genetic summaries, Jerseys have a 180-day, or six-month advantage in Productive Life among the six dairy breeds evaluated in the United States.
For cows born over a five-year period—1998 through 2002—Jerseys have the longest average productive life of 33.6 months, or 1,025 days. A total of 204,383 Jerseys were included in the data published by the USDA Animal Improvement Programs Laboratory (AIPL) at Beltsville, Md.
By comparison, the weighted average for 3,290,970 cows of the other five breeds born in the same period is 27.7 months, or 845 days. By breeds, average Productive Life for Ayrshire is 967 days (11,672 cows); Brown Swiss, 930 days (29,311 cows); Guernsey, 803 days (16,223 cows); Holstein, 844 days (3,230,119 cows); and Milking Shorthorn, 948 days (3,645 cows).
The trait of Productive Life is defined as "time in the milking herd before removal by voluntary culling, involuntary culling, or death.”
Cows having opportunity to reach eight (8) years of age are considered a completed observation, but continue to add credits for productive life after this point.
Productive Life evaluations combine information from direct longevity (measured by DHI data on calving dates, disposal dates, reasons for disposal and lactation lengths) with correlated traits. Cows with multiple lactations are given more total credit for productive life than cows with just one long lactation. According to AIPL scientists, this is because "cows that begin a next lactation generally are more profitable than those that continue the previous lactation because a new peak yield is achieved.” As a cow's lactation is extended, the value credited to her production is diminished.