Effect of Dietary Fat in Isocaloric Rations on the Nitrogen Content of Milk From Holstein Cows

Effects of dietary fat on milk composition, particularly milk N, were evaluated using 12 lactating Holstein cows in a replicated 4×4 Latin-square design. Four complete mixed diets were formulated to contain either 0 or 3.5% added fat (grease) and either 1.6 or 1.7 Mcal NE1 (0, 1.6; 0, 1.7; 3.5, 1.6;...

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Bibliographic Details
Published in:Journal of dairy science 1989-11, Vol.72 (11), p.2949-2957
Main Authors: DePeters, E.J., Taylor, S.J., Baldwin, R.L.
Format: Article
Language:English
Subjects:
AGE
Amino Acids - blood
Animal Feed
Animals
BLOOD COMPOSITION
BOVIN LAITIER
BREEDS
Caseins - analysis
Cattle - metabolism
Cattle - physiology
Cholesterol - blood
COMPOSICION
COMPOSICION DE LA SANGRE
COMPOSITION
COMPOSITION DU SANG
CONTENIDO DE NITROGENO
CORPS GRAS
COWS
DAIRY CATTLE
Dietary Fats - metabolism
EDAD
FATS
Fatty Acids - analysis
Fatty Acids, Nonesterified - blood
Fatty Acids, Volatile - analysis
Female
GANADO DE LECHE
GRASAS
HOLSTEIN-FRIESIAN
LACTACION
LACTATION
LAIT
LECHE
MILK
Milk - analysis
MILK YIELD
Nitrogen - analysis
NITROGEN CONTENT
Pregnancy
RACE
RACION
RATION
RATIONS
RAZAS
RENDEMENT LAITIER
RENDIMIENTO LECHERO
TENEUR EN AZOTE
Triglycerides - blood
VACA
VACHE
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Summary:Effects of dietary fat on milk composition, particularly milk N, were evaluated using 12 lactating Holstein cows in a replicated 4×4 Latin-square design. Four complete mixed diets were formulated to contain either 0 or 3.5% added fat (grease) and either 1.6 or 1.7 Mcal NE1 (0, 1.6; 0, 1.7; 3.5, 1.6; and 3.5, 1.7). Diets were fed for ad libitum intake, and periods were 21 d. Adding fat to the diet depressed total milk N, casein N, and whey protein N concentration compared with no added fat at both energy densities. The proportion of total N in the casein fraction was not affected by dietary fat, whereas the proportion of N associated with the NPN fraction was increased with diets containing added fat. The high concentrate diet (0, 1.7) contained the highest content of milk N and casein N. Added dietary fat increased the proportion of long-chain fatty acids (C18 and C18:1) in milk fat and decreased the proportion of short-chain fatty acids (C8 to C16). Daily milk yield was higher for the high energy fat diet (3.5, 1.7) than for the other three diets, which were similar. Blood concentrations of triglycerides, nonesterified fatty acids, and cholesterol were increased by diets containing added fat.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.S0022-0302(89)79447-9