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Milk production and feed intake responses to increasing levels of palmitic acid supplementation in early lactation Holstein cows.

P. D. French

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06-23-2020

Abstract:

178
Milk production and feed intake responses to increasing levels of palmitic acid supplementation in early lactation Holstein cows.
P. D. French*1, M. J. Martin2. 1PHD R&D LLC Fort Atkinson, WI, 2University of Wisconsin Madison, WI.

Several published studies show that mid-lactation Holstein cows of varying production levels respond to increasing levels of palmitic acid (PA) supplementation. We evaluated the dose-dependent response of a PA supplement in early lactation Holstein cows fed a basal diet containing 2.6% total fatty acids (FA) and 0.5% PA. Twelve multiparous, Holstein cows (53 � 15 DIM) with a preliminary milk yield of 62 � 8 kg/d were fed a PA supplement (88.0% C16:0, 3.6% C18:0, 5.1% C18:1) at 0, 0.5, 1.0, or 1.5% of ration DM in a replicated 4 � 4 Latin square design. Periods were 14 d with the final 5 d used for data collection except for milk composition and yield which was determined on the last 2 d of each period. Cows were milked 3x/d and fed a TMR once daily that contained 54% forage (35% corn silage and 19% alfalfa silage), 15.8% CP, 27.7% NDF, and 28.4% starch. Data were analyzed using the mixed model procedure of SAS and linear (L), quadratic (Q), and cubic (C) contrasts were used to evaluate PA dose-response. Results are presented in the following order: 0, 0.5, 1.0, or 1.5% PA. PA intake was 151, 297, 436, and 573 g/d. PA dose increased milk yield (60.1, 59.9, 61.4, and 61.6 kg/d; L, P < 0.01) and ECM (59.8, 58.9, 61.8, and 60.9 kg/d; L, C, P < 0.01). PA dose affected DMI (30.1, 31.6, 31.6, and 31.5 kg/d; Q, P < 0.05) and ECM feed efficiency (1.94, 1.88, 1.97, and 1.95; C, P < 0.01). Milk fat concentration (3.52, 3.44, 3.59, 3.53%; C, P < 0.05), milk FA acid concentration (3.33, 3.26, 3.40, and 3.34; C, P < 0.05) and milk fat yield (2.16, 2.10, 2.26, 2.20 kg/d; C, P < 0.01) were affected by PA dose. PA did not alter milk protein concentration (2.90%) but did affect yield (1.78, 1.77, 1.84, and 1.79 kg/d; C, P < 0.01; L, P < 0.08). Preformed FA (>C18) increased with PA dose (L, P < 0.05), whereas mixed FA (C16) responded cubically (P < 0.05), and de novo (<C16) were not affected by PA dose. In conclusion, high-producing Holstein cows responded most efficiently to 1.0% PA supplementation.

Keywords: fat supplementation, feed efficiency, milk fat.