title: Starch levels on performance, milk composition and energy balance of lactating dairy cows.
abstract: The objective of this experiment was to evaluate the effects of starch levels in diets with the replacement of citrus pulp for corn on milk yield, milk composition, and energy balance of lactating dairy cows. Twenty-eight multiparous Holstein cows were used in seven 4 × 4 Latin squares conducted concurrently, and each experimental period consisted of 20 days (16 days for adaptation and 4 days for sampling). The experimental treatments comprised four starch levels: 15, 20, 25, and 30% in the diet. The dry matter intake increased linearly with increasing starch levels. The milk yield and 3.5% fat-corrected milk yield showed quadratic response to increasing starch levels. The milk protein content and milk total solids content responded linearly to increasing starch levels. The feed efficiency, milk lactose content, milk urea nitrogen, plasma urea nitrogen, and plasma glucose concentration were not affected by starch levels. The estimated net energy for lactation (NEL) intake increased linearly as the starch level was raised. Although the milk NEL output per kilogram of milk was not affected by starch, the milk NEL output daily responded quadratically to starch levels. In addition, the NEL in body weight gain also responded quadratically to increasing starch levels. The efficiency of energy use for milk yield and the NEL efficiency for production also responded quadratically to increasing starch levels. Diets for mid-lactating dairy cows producing around 30 kg/day of milk should be formulated to provide around 25% starch to optimize performance.
authors.affiliation: Department of Animal Science, University of São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Carolina Almeida
authors.initials: CA
authors.lastname: Carmo
authors.forename: Fernanda
authors.initials: F
authors.lastname: Batistel
authors.forename: Jonas
authors.initials: J
authors.lastname: de Souza
authors.forename: Junio Cesar
authors.initials: JC
authors.lastname: Martinez
authors.forename: Paulo
authors.initials: P
authors.lastname: Correa
authors.forename: Alexandre Mendonça
authors.initials: AM
authors.lastname: Pedroso
authors.forename: Flávio Augusto Portela
authors.initials: FA
authors.lastname: Santos
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D002417:Cattle; D003612:Dairying / Q000379:methods*; D004032:Diet / Q000662:veterinary; D002149:Energy Intake; D004734:Energy Metabolism; D005260:Female; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry; D013213:Starch / Q000737:chemistry*; D013696:Temperature; D015430:Weight Gain; D003313:Zea mays
chemical_list: D008894:Milk Proteins; D013213:Starch