Historically, negative dietary cation-anion difference (DCAD) diets have been fed for 2 to 3 weeks prepartum to reduce the incidence of clinical hypocalcemia or milk fever. Limited information is available on the effect of feeding a negative DCAD for extended time prepartum. A trial was conducted to evaluate the effects of feeding a negative DCAD diet for 3, 4, or 6 weeks prepartum.
The transition from late gestation to lactation requires enormous physiological adaptations by the dairy cow, which can significantly affect the following lactation and subsequent reproduction. Nutrition management during the transition period is challenged by reduced DMI during the late-gestation period coupled with a drastic increase in nutrient requirements following calving. One of the most significant challenges involves calcium (Ca) levels in the cow and can result in clinical or subclinical hypocalcaemia. Studies report that cows experiencing clinical hypocalcaemia during the time immediately after calving produced 14% less milk than cows with normal serum Ca concentrations. In addition to decreased milk yield, cows that experienced clinical or subclinical hypocalcaemia are at greater risk for developing other metabolic disorders. Feeding negative DCAD diets prepartum stimulated Ca absorption and mobilization, thus preventing hypocalcaemia, and maintained DMI and improved milk yield postpartum.
Before the trial, all cows were fed a high-forage, low-energy diet. During the trial, cows were fed a diet formulated for late gestation (14.6% CP, 42.3% NDF, 20.5% starch, 7.1% ash, and 0.97% Ca) supplemented with Animate, with a resulting DCAD (Na + K − Cl − S) of −21.02 mEq/100 g of DM. Cows were split into one of three treatments and fed the negative-DCAD diet for 3 (3W), 4 (4W), or 6 wk (6W) before predicted calving. After calving, cows were fed a diet formulated for early lactation (18.0% CP, 36.4% NDF, 24.2% starch, 8.1% ash, and 0.94% Ca) for the following 6 wk with a DCAD of 20.55 mEq/100 g of DM.
Urine pH was not different among treatments before calving and averaged 6.36. No differences were observed in prepartum DM intake, which averaged 11.4, 11.5, and 11.7 kg/d for 3W, 4W, and 6W, respectively. Prepartum serum total protein, albumin, and Ca concentrations, and anion gap were within normal limits but decreased linearly with increasing time cows were fed a negative-DCAD diet. No differences were observed in serum metabolite concentrations on the day of calving.
No differences were observed in postpartum DM intake, milk yield, or concentration of fat or protein among treatments. Results of this trial indicate that no differences existed in health or milk production or components in cows fed a negative-DCAD diet for up to 6 wk prepartum compared with those fed a negative-DCAD diet for 3 or 4 wk prepartum. From an applied application standpoint, these collective data support the use of negative-DCAD diets in 1-group dry cow programs.