Mineral status in beef cows fed broiler litter diets with cation-anion differences or supplemented with hay

Two studies were conducted to evaluate mineral status of beef cows consuming broiler litter (BL). During the first study, three diets (hay, BL + corn + hay, and BL + corn + hay + NH4C1) were fed to 45 pregnant cows from December through May to evaluate the effect of decreasing the dietary cation-anion difference (DCAD). Dry matter intake was not affected (P > .05) by treatments. Serum Ca was suppressed (P < .05) in cows consuming BL at 101 d prepartum. Serum hydroxyproline concentrations were suppressed (P < .05) before, at, and after parturition in cows consuming BL, whereas parathyroid hormone concentrations were not influenced (P > .05) by diet. Estimated digestibilities of OM, ADF, NDF, and hemicellulose were decreased (P < .05) for BL diets at midgestation, whereas only the fiber portions of the BL diets were decreased at parturition in BL diets compared with hay. Apparent absorption of Ca was greater (P < .05) for BL diets at midgestation; however, this difference was not observed at parturition. No differences (P > .05) were determined for milk or urine excretion of Ca. For the second study, three diets (hay, BL + corn, and BL + corn + hay) were fed to 48 cows. Serum Ca was suppressed (P < .05) in cows consuming BL diets, and serum hydroxyproline was greater (P < .05) in cows consuming the hay-supplemented diet than in those consuming BL without hay. Lowering the DCAD was not effective in offsetting the serum Ca changes observed; however, supplementing hay may allow for more bone resorption of Ca at a time when cows are in need of increased Ca.