Effect of limestone reactivity and percent on production by dairy cows in early lactation.
Seventy-two Holstein cows (16 first lactation) were assigned to four treatments: A) normal-grind limestone (800 to 1000 mu) added to provide .77% calcium (total ration dry basis); B) fine-grind limestone (less than 150 mu) 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.
D000818:Animals; D001835:Body Weight; D002119:Calcium Carbonate / Q000008:administration & dosage*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002417:Cattle / Q000502:physiology*; D005260:Female; D007774:Lactation; D050356:Lipid Metabolism; D008892:Milk / Q000378:metabolism*; D008894:Milk Proteins / Q000378:metabolism; D010316:Particle Size; D011247:Pregnancy
D002136:Calcium, Dietary; D008894:Milk Proteins; D002119:Calcium Carbonate