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Oscillating dietary starch had minor effects on performance in Holstein cows.

M. Larsen

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06-23-2020

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Abstract:

T152
Oscillating dietary starch had minor effects on performance in Holstein cows.
M. Larsen*, P. Lund, L. E. Hern�ndez-Castellano, M. R. Weisbjerg. Department of Animal Science, Aarhus University-Foulum Tjele, Denmark.

The effect of oscillating dietary starch on performance was investigated in 72 Holstein cows for 5 weeks in a randomized design. Cows were blocked according to parity and lactation stage. Cows were loose-housed with automatic milking (AMS) and automatic feed registration. Dietary starch was either stable (STA) or oscillating (OSC) in 2-d intervals with � 20 g/kg DM at either 190 (LO) or 230 (HI) g starch/kg DM in a 2 � 2 factorial arrangement. Diets contained (g/kg DM) 257 corn silage, 257 grass-clover silage, 138 AMS concentrate, 80 canola cake, 40 soybean meal, 14 minerals+vitamins, as well as 119 rolled barley and 95 dried sugar beet pulp with LO starch or 182 rolled barley and 32 dried sugar beet pulp with HI starch. Oscillation was made by substituting 64 g/kg DM of dried sugar beet pulp with rolled barley at each starch level. Milk samples were collected the last 2 d of each week. Rumen fluid (oro-ruminal) and blood was collected from 36 cows. Data were analyzed with wk 0 as covariate and block, starch level, oscillation, week (repeated within cow), and possible interactions as fixed effects. The AMS concentrate intake did not differ among treatments (2.6 � 0.1 kg/d; P > 0.30). Total DMI was greater with OSC-HI and STA-LO compared with the 2 other treatments (23.5 vs. 22.9 � 0.3 kg/d; interaction: P = 0.02). The ECM yield was greater with OSC-HI and STA-LO compared with the 2 other treatments (37.2 vs. 36.1 � 0.5 kg/d; interaction: P = 0.03). The effects on DMI and ECM were minor and the pattern difficult to relate to oscillation. Milk protein content was higher for HI compared with LO (3.50 vs. 3.45 � 0.02%; P = 0.02). Milk fat content was higher for OSC compared with STA (4.01 vs. 3.85 � 0.05%; P = 0.01). Rumen propionate proportion was greater with HI compared with LO (P = 0.02), and butyrate proportion tended to be greater with OSC compared with STA (P = 0.09). Plasma glucose did not differ among treatments (P > 0.51), FFA was lower with HI compared with LO (P = 0.03), and BHB was numerically greater with OSC compared with STA (P = 0.16). The effects on milk components could be related to differences in rumen and plasma metabolites.

Keywords: starch, oscillating, production.