Effect of feeding calcareous marine algae to Holstein cows prepartum or postpartum on serum metabolites and performance

Thirty-six multiparous Holstein cows and 12 springing heifers were used in a 9-wk randomized design trial to determine the response of cows fed calcareous marine algae (CMA) beginning 3 wk prepartum or after parturition through 6 wk postpartum on dry matter intake (DMI), blood and urine metabolites, and milk yield and composition. Within parity and expected calving date, cows were assigned randomly to 1 of 4 treatments with a 2 × 2 factorial arrangement. Prepartum diets were supplemented with calcium carbonate (CON) or 50 g/d of CMA with a resulting dietary cation-anion difference of −5.17 and −3.99 mEq/100 g, respectively. Postpartum diets were formulated to provide either 317 g/d of sodium bicarbonate and calcium carbonate (NBC) or 100 g/d of CMA, providing a dietary cation-anion difference of 35.58 and 15.64 mEq/100 g, based on 25 kg/d of DMI, respectively. No differences were observed in prepartum DMI or postpartum DMI, milk yield, percentage of milk fat, protein, lactose, and solids-not fat among treatments. Milk protein yield was higher for cows fed CMA prepartum compared with CON. Interactions of prepartum treatment and week were observed for yield of milk fat and energy-corrected milk because of higher yields for cows fed CMA during wk 2 and 6 compared with CON. Serum Na concentrations were greater for cows fed CON prepartum or NBC postpartum compared with CMA. Postpartum urinary concentrations of Na exhibited an interaction among treatments and were higher for CON-NBC and CMA-NBC compared with CON-CMA and CMA-CMA. Similar interactions of treatments were also observed for serum urea N and creatinine postpartum. Postpartum urinary K concentrations were higher for cows fed CMA postpartum compared with NBC. Results of this trial indicate that feeding cows CMA prepartum does not affect DMI or serum metabolites prepartum, but does support higher milk protein yield. Performance and serum metabolite concentrations of cows fed CMA postpartum were comparable with that of cows fed NBC, except for changes in serum and urinary concentration of Na, which was a function of dietary Na intake.