title: Concentrate: forage ratio in the diet of dairy cows does not alter milk physical attributes.
abstract: This study aimed to evaluate the effect of concentrate-to-forage ratio (C:F) on the performance, blood profile, and milk physicochemical characteristics of mid-lactation cows fed a corn silage-based diet. Twenty four Holstein cows, with BW 575 ± 70 kg, body condition score (BCS) 3.1 ± 0.2, milk yield 18.4 ± 3.0 kg, and days in milk (DIM) 121 ± 21 were randomly allocated into three treatments with C:F ratios of 35:65, 45:55, and 55:45 on a dry matter (DM) basis. Data was submitted to analyses of variance and regression. Increasing C:F from 35 to 55 % linearly enhanced milk production (22 to 23.6 kg day(-1)) and serum urea nitrogen (16.8 to 19.6 mg/dL), while it linearly reduced lactose and fat in milk (4.8 to 4.6 %; 3.9 to 3.6 %, respectively). Body weight, BCS, milk acidity, ethanol stability, coagulation time, and milk and blood mineral contents did not differ among treatments. During the last period of measurements, increased C:F reduced urinary pH and milk urea nitrogen. Changes of concentrate-to-forage proportion from 35 to 55 % increased milk yield, altered chemical composition without changing BW, BCS, acidity, stability, and mineral content of milk and blood attributes.
authors.affiliation: FAI Faculdades, Rua Carlos Kummer, 100, Universitário, Itapiranga, SC, 89896-000, Brazil.
authors.forename: Sandro Charopen
authors.initials: SC
authors.lastname: Machado
authors.forename: Concepta Margareth
authors.initials: CM
authors.lastname: McManus
authors.forename: Marcelo Tempel
authors.initials: MT
authors.lastname: Stumpf
authors.forename: Vivian
authors.initials: V
authors.lastname: Fischer
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D005260:Female; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000737:chemistry*; D012820:Silage / Q000032:analysis*; D003313:Zea mays