title: Influence of a reduced-starch diet with or without exogenous amylase on lactation performance by dairy cows.
abstract: The objective of this trial was to determine lactation performance responses in high-producing dairy cows to a reduced-starch versus a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Forty-five multiparous Holstein cows, 68±29 d in milk and 696±62 kg of body weight (BW) at trial initiation, were randomly assigned to 1 of 3 treatments in a completely randomized design; a 2-wk covariate adjustment period with cows fed the normal-starch diet was followed by a 10-wk treatment period with cows fed their assigned treatment diets. The normal-starch total mixed ration did not contain exogenous amylase (NS-). The reduced-starch diets, formulated by partially replacing corn grain and soybean meal with whole cottonseed and wheat middlings, were fed without (RS-) and with (RS+) exogenous amylase addition to the total mixed ration. All diets contained 50% forage and 19.8% forage neutral detergent fiber (dry matter basis). Starch and neutral detergent fiber concentrations averaged 27.0 and 30.9%, 22.1 and 35.0%, and 21.2 and 35.3% (dry matter basis) for the NS-, RS-, and RS+ diets, respectively. Expressed as a percentage of BW, dry matter intake was greater for cows fed RS- than for cows fed NS- or RS+. Intake of neutral detergent fiber ranged from 1.09 to 1.30% of BW among the treatments, with that of RS- being 21% greater than that of NS-. Milk yield tended to be greater for cows fed NS- compared with the RS diets. Milk fat content and yield were unaffected by treatment. Milk protein content and yield were greater for cows fed NS- compared with the RS diets. Concentrations of milk urea nitrogen were greater for cows fed RS diets compared with the NS- diet. Body weight, BW change, and body condition score were unaffected by treatment. Feed conversion (kg of milk/kg of dry matter intake) was 10% greater on average for cows fed NS- than for cows fed the RS diets, and tended to be 6% greater for cows fed RS+ compared with RS-. Feeding a reduced-starch diet formulated by partially replacing corn grain and soybean meal with a wheat middlings and whole cottonseed mixture compared with a normal-starch diet without addition of exogenous amylase to either diet reduced milk and component-corrected feed conversions. Addition of exogenous amylase to a reduced-starch diet was of minimal benefit in this study.
authors.affiliation: Department of Dairy Science, University of Wisconsin-Madison, 1675 Observatory Dr., Madison, USA.
authors.forename: L F
authors.initials: LF
authors.lastname: Ferraretto
authors.forename: R D
authors.initials: RD
authors.lastname: Shaver
authors.forename: M
authors.initials: M
authors.lastname: Espineira
authors.forename: H
authors.initials: H
authors.lastname: Gencoglu
authors.forename: S J
authors.initials: SJ
authors.lastname: Bertics
mesh_terms: D000681:Amylases / Q000008:administration & dosage*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D050528:Diet, Carbohydrate-Restricted / Q000662:veterinary*; D005260:Female; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000378:metabolism; D013213:Starch / Q000378:metabolism*
chemical_list: D013213:Starch; D000681:Amylases