Managing Reproduction in Dairy Cattle: III. Changes in Culling Patterns with Increased Reproduction

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Abstract
The effects of a management system on changes in culling patterns were determined with observations from 1182 lactations. From 1968-1972, 307 of 471 cows were culled. Management was synchronization of estrus of lactating dairy cattle by administration of a progestogen, melengestrol acetate, at 1 mg/head per day usually for 14 days, beginning between 14 and 55 day postpartum. The rate of culling in the lactation coincident with treatment was less for treated than for control cows (16% vs. 25%). Of the treated cows culled in the lactation of treatment, 22% were removed for failure to reproduce, vs. 31% of the control cows culled for the same reason. Of the control cows, 20% were removed for low milk production, vs. 42% of the treated cows which were removed for the same reason. Culling for other reasons (dairy sale, death, injury, etc.) and for mastitis or poor udder were similar for treated (18% and 18%) and control cows (24% and 25%). Administration of melengestrol acetate for several lactations had no detrimental effects. Culling of treated cows for reproduction remained below that for control cows. Culling for milk production of treated cows decreased and culling for mastitis or poor udder increased slightly. Cows which were culled in the 1st year following complete removal of melengestrol acetate had a culling pattern similar to the control cows. Overall the progestogen system for managing reproduction shifted cause of culling from reproduction to milk production.