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Low starch diets improve dry matter intake and energy balance in early lactating Holstein dairy cows.

N. Juliano



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Low starch diets improve dry matter intake and energy balance in early lactating Holstein dairy cows.
N. Juliano*1,5, M. F. Olmeda2,5, L. M. Buraschi3, M. V. Dunleavy4, F. Bargo5, R. A. Palladino1,5. 1Consejo Nacional de Investigaciones Cient�ficas y T�cnicas (CONICET) Buenos Aires, Argentina, 2Universidad de Lomas de Zamora Buenos Aires, Argentina, 3Universidad Nacional de Mar del Plata Buenos Aires, Argentina, 4Instituto de Patobiolog�a, Instituto Nacional de Tecnolog�a Agropecuaria Buenos Aires, Argentina, 5PROLACT (UNLZ-FIL) Buenos Aires, Argentina.

The aim of this study was to evaluate low starch (LS) and high starch (HS) diets and its effect on DMI, energy balance (EB), milk yield and composition, energy-corrected milk (ECM), BW and body condition score (BCS, 1—5 scale) changes in early lactating Holstein dairy cows. Twenty-four Holstein cows (12 multiparous, 554.61 � 25.12 kg BW; 12 primiparous; 568.63 � 23.52 kg BW; mean � SD) were assigned to 1 of 2 treatments at calving during 28 d: LS and HS. Diets consisted in corn silage plus pelleted concentrate formulated to be iso-energetic and iso-nitrogenous, on a 50:50 forage to concentrate ratio. Dietary treatments were adjusted by altering concentrations of corn grain and soyhulls to reach a target of 22 and 28% starch for LS and HS respectively. The DMI and milk yield were measured daily and milk composition, BW and BCS were measured weekly. Blood samples were taken from the jugular vein at 1, 7, 14, 21 and 28d since calving and analyzed for glucose, NEFA, BHB, insulin and IGF-1. The EB was calculated using DMI, energy consumption, BW changes and the estimated requirements based on milk production and composition (NRC, 2001). Data were analyzed using the mixed procedure of SAS (University Edition, 2018), as a randomized complete block design, with the animal nested to treatment as random effect, parity, day, treatment and their interaction as fixed effects. Cows fed LS diet had higher DMI compared with HS (20.57 vs. 17.83 kg/d, P < 0.01), with no treatment x parity interaction. There were no differences (P > 0.05) in milk yield (25.03 � 1.21 kg/d), ECM (27.26 � 1.68 kg/d), fat % (3.97 � 0.21%) and protein % (3.59 � 0.07%), BW (536.49 � 17.1 kg) and BCS changes (0.25 � 0.12 units) between treatments. No differences between treatments were found for blood metabolites and hormones. Cows fed LS diet had a less estimated negative EB with shorter duration (−0.06 vs. −4.22 Mcal NEl/d; 14 vs 28d, P < 0.05). These results show that lowering starch levels in early lactation diets has a positive effect on both DMI and EB, and may shorten the negative EB period.

Keywords: energy balance, starch level, transition period.