Joint Effects of Parity, Age, and Season of Kidding on Milk and Fat Yields in Dairy Goats

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Abstract
Dairy Herd Improvement 305-day lactation records of 120 days or more were examined for joint effects of parity, age, and season of kidding on milk and fat yields in Alpine, Saanen, and Toggenburg goats. Parity classifications were 1st, 2nd, 3rd, and 4th or greater. Seasons of kidding were Dec.-March and April-July. Data were analyzed within geographical regions: (1) western coastal states plus their bordering inland states and (2) northeastern and north-central states. There were 6187 records from 1 covering 1970-1978 and 4350 records from 2 covering 1969-1978. In both regions, parity contrasts across age-season were large, generally significant and indicated the need to consider parity in addition to age and season in developing age correction factors for dairy goat lactations. Previous lactation experience, seasonal breeding patterns and onset of estrus may contribute to parity and age relationships with milk and fat yields. Repeatabilities of milk and fat yields were 0.45 and 0.43 for region 1 and 0.48 and 0.45 for region 2.