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Effect of oscillating dietary starch on metabolic and acidotic status of lactating dairy cows.

M. Larsen

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06-23-2020

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Abstract:

T144
Effect of oscillating dietary starch on metabolic and acidotic status of lactating dairy cows.
L. E. Hern�ndez-Castellano, L. L. Pereira dos Santos, M. Larsen*. Dept. Animal Science, Aarhus University-Foulum Tjele, Denmark.

Six lactating multiparous Holstein cows (150 � 49 DIM) with rumen cannulas and intercostal arterial catheters were used in a replicated 3 � 3 Latin square with 3 levels of oscillating (OSC) dietary starch to study the effect on metabolic and acidotic status. From d 1 to 7, cows were fed ad libitum with a control diet containing 20% starch (DM basis); from d 8 to 14 diets oscillated from 20 to 28 (LO), 35 (ME), or 42% (HI) starch. At d 8 and 14, ventral and medial rumen fluid, blood, and urine samples were collected at —0.5, +1, +2.5, +4, +5.5, and +7 h relative to morning feeding. Data were analyzed with OSC level, day, time, and possible interactions as fixed effects. Time was considered repeated. Level of OSC did not affect DMI at either d 8 or 14 (20.4 � 1.2 and 20.6 � 1.3 kg; respectively; P > 0.31) or milk yield (30.5 � 1.2 and 28.9 � 1.2 kg, respectively; P > 0.33). Medial rumen pH was affected by OSC level (P = 0.03; OSC level � day � time interaction). In cows with HI oscillation, medial rumen pH decreased continuously at both d 8 and 14 from —0.5 h (5.66 � 0.14 and 6.21 � 0.14, respectively) to +7 h (5.13 � 0.14 and 5.24 � 0.14, respectively) relative to morning feeding. With LO and ME oscillation at d 8, medial rumen pH decreased from —0.5 h (5.69 � 0.14 and 5.69 � 0.14, respectively) and reached nadir at +4 h (5.54 � 0.14 and 5.35 � 0.14, respectively) relative to morning feeding. Similarly at d 14, cows with LO and ME oscillation medial rumen pH decreased from —0.5 h (5.89 � 0.14 and 5.92 � 0.14, respectively) and reached nadir at +2.5 h (5.40 � 0.14 and 5.44 � 0.14, respectively) relative to morning feeding. However, OSC level did not affect ventral rumen pH (P > 0.17), blood pH (P > 0.15) or urine pH (P > 0.57). Plasma glucose tended (P = 0.07) to increase proportionally with OSC level (3.87 � 0.07, 3.96 � 0.07 and 4.02 � 0.07 with LO, ME, and HI oscillation, respectively), while OSC level did not affect plasma concentrations of BHB (P > 0.38) or D-lactate (P > 0.11). In conclusion, oscillating dietary starch decreased medial rumen pH, especially high level of starch oscillation, whereas blood and urine pH did not provide any indication of systemic acidosis.

Keywords: starch, oscillating, metabolism.