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Effects of feeding a negative DCAD diet prepartum for varied lengths of time on serum metabolites and performance
Forty-five multiparous Holstein cows and 15 springing heifers were used in a completely randomized design trial to determine the effect of length of feeding a negative DCAD diet prepartum on serum metabolites, DMI, milk yield and composition. After training to eat through Calan doors, cows within parity were assigned randomly to negative DCAD diets for 3 (3WPC), 4 (4WPC) or 6 wk (WPC) before predicted calving. Actual days cows were fed negative DCAD diets was 19.2 ± 4.1, 27.9 ± 3.1, and 41.5 ± 4.1d for 3WPC, 4WPC, and 6WPC, respectively. All 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 (Prince Agri Products, Inc., Quincy, IL) with a resulting DCAD (Na + K – Cl –S) of -21.02 mEq/100g DM. 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 DM. Urine pH was not different (P > 0.10) among treatments prior to calving and averaged 6.36. No differences (P > 0.10) were observed in prepartum DMI which averaged 11.4, 11.5 and 11.7 kg/d for 3WPC, 4WPC, and 6WPC, respectively. Prepartum serum total protein (P = 0.03), albumin (P = 0.01), Ca (P = 0.02), and anion gap (P < 0.01) 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. After calving, serum total protein (P = 0.04) and globulin (P = 0.02) increased linearly with increasing time cow’s were fed a negative DCAD diet. No differences were observed in postpartum DMI, milk yield, or concentration of fat or protein among treatments: 19.1, 40.6, 4.30, and 2.80; 19.6, 41.5, 4.50, and 2.90; and 18.6 kg/d, 41.0 kg/d, 4.30% and 2.73% for 3WPC, 4WPC, and 6WPC, respectively. Results of this trial indicate that extending the length of time cows are fed a negative DCAD diet does not negatively affect serum metabolites or resulting performance.
Keywords: DCAD, serum metabolites, milk yield, milk composition