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Abstract
Effects of supplementing calcareous marine algae (CMA) and optimal length of feeding negative dietary cation-anion difference (DCAD) were evaluated. In trial one, no differences were observed in DMI, milk yield, or concentrations of milk components when cows were fed diets supplemented with CMA starting either prepartum or postpartum. Milk protein yield was higher for cows fed CMA prepartum compared with those without supplemental CMA. Milk fat yield and ECM were higher for cows fed CMA prepartum during week 2 and 6. Concentrations of serum Na were greater and urinary K was lower for cows fed sodium bicarbonate postpartum compared with CMA. In trial two, no differences were observed in DMI, milk yield and components due to the length of time cows were fed a negative DCAD diet prepartum. Increasing time feeding negative DCAD prepartum linearly decreased prepartum serum total protein, albumin, and Ca, and increased postpartum serum total protein and globulin concentrations. Feeding a negative DCAD diet starting from 4 wk prepartum resulted in the lowest urine pH on day of calving and highest milk protein percentage during wk 3, 5, and 6 compared with cows fed a negative DCAD diet for 3 or 6 wk prepartum. These trials indicate that feeding CMA prepartum does not affect DMI or serum metabolites prepartum, but supported improvements in animal performance postpartum. Feeding CMA postpartum supported similar performance and serum metabolite concentrations compared with feeding sodium bicarbonate. Extending the length of time a negative DCAD is fed prepartum up to 42 days does affect select serum metabolites, but has no negative impact on health, milk production and components.