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1503
The effect of metabolizable protein supply for dry Holstein dairy cows on periparturient feed intake, metabolism, and lactation performance
Some nutritionists increase metabolizable protein (MP) supply for dry cows to improve subsequent lactation performance and health based on field observations. This study determined the effect of MP supply during the dry period on dry matter intake (DMI), metabolism, and early lactation performance. Eighty Holstein cows that had completed ≥1 lactation were assigned randomly to treatments: 1) a 55-d dry period with ~84 g MP/kg DMI in the far-off [13.1% crude protein (CP), 9.4% starch, 51.7% neutral detergent fiber (NDF)] and close-up (12.9% CP, 14.9% starch, 47.0% NDF) diets (LMP55), 2) a 55-d dry period with ~84 g MP/kg DMI in the far-off diet (13.1% CP, 9.4% starch, 51.7% NDF ) and ~108 g MP/kg DMI in the close-up diet (14.5% CP, 15.1% starch, 43.0% NDF; LHMP55), and 3) a 43-d dry period with ~108 g MP/kg DMI in a 1-group diet (14.5% CP, 15.1% starch, 43.0% NDF; HMP43). Close-up diets were fed for 3 wk before expected calving. Dry diets supplied ≥29 g Met/d and ≥91 g Lys/d. A fresh diet (15.6% CP, 21.7% starch, 33.5% NDF) was fed for 2 wk and then a high diet (15.2% CP, 26.1% starch, 30.2% NDF) was fed for 10 wk. Diets were modeled with CNCPS v6.5. Cows were individually fed 1×/d, group housed, and milked 3×/d. Milk was sampled weekly. Coccygeal blood was collected -3 to 2 wk relative to calving. Data were analyzed as a completely randomized design by ANOVA with the MIXED procedure of SAS with model effects of treatment, time, and treatment × time. Metabolism and lactation performance were not improved by providing additional MP during the dry period compared with a lower MP diet that met the Met and Lys requirements.
Keywords:
dry period, metabolizable protein, transition cow