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Effect of Limestone Reactivity and Percent on Production by Dairy Cows in Early Lactation

Agway Inc., Syracuse NY 13221
and Cooperative Research Farms, Charlotteville, NY 12036

ABSTRACT

Seventy-two Holstein cows (16 first lactation) were assigned to four treatments: A) normal-grind limestone (800 to 1000 µ) added to provide .77% calcium (total ration dry basis); B) fine-grind limestone (<150 µ) at .77% calcium; C) normal-grind at 1.15% calcium; and D) fine-grind limestone at 1.15% calcium.

Cows fed diets containing .77% calcium had higher percent milk fat and fat yield than those fed 1.15% calcium diets, and cows fed fine-grind limestone had greater percent fat and fat yield than those fed normal-grind limestone. Four percent fat-corrected milk was higher for cows fed .77% calcium diets. Trends were similar for heifers in first lactation.

Dry matter intake was higher for cows fed .77% calcium diets, and nutrient efficiency for milk synthesis favored cows fed fine-grind 1.15% calcium. Fecal pH was higher during wk 4 on treatment for cows fed high calcium diets; however, 8 wk were not different. Fecal starch and calcium and phosphorus in plasma were not different between treatments: however, heifers fed fine-grind 1.15% calcium showed a decrease of fecal starch with time.