Incorporation of endogenous urea nitrogen into amino acids of milk in goats fed diets with various protein levels
PBN-AR
Instytucja
Instytut Fizjologii i Żywienia Zwierząt im. Jana Kielanowskiego Polskiej Akademii Nauk
Informacje podstawowe
Główny język publikacji
en
Czasopismo
Journal of Animal and Feed Sciences
ISSN
1230-1388
EISSN
Wydawca
THE KIELANOWSKI INSTITUTE OF ANIMAL PHYSIOLOGY AND NUTRITION
DOI
Rok publikacji
2014
Numer zeszytu
3
Strony od-do
212-216
Numer tomu
23
Identyfikator DOI
Liczba arkuszy
Słowa kluczowe
en
endogenous urea
15N
dietary protein
milk
amino acids
dairy goats
Streszczenia
Język
en
Treść
ABSTRACT. The aim of the study was to estimate how much endogenous urea nitrogen (EUN) was incorporated into various amino acids of milk protein when goats were fed low (LP), medium (MP), or high protein (HP) diets in a 3 × 3 Latin-square design. Three Alpine goats of about 35 kg body weight fitted with a catheter into the jugular vein were fed isoenergetic diets containing 11% (LP), 13% (MP), or 16% (HP) crude protein in dry matter. They were continuously infused with 15N urea into the jugular vein for 6 days. Daily milk yield was 1.58, 1.49 and 1.77 g. Milk urea concentrations were 139, 342 and 451 mg · l–1, whereas plasma urea was 178, 356 and 667 mg · l–1 in groups LP, MP and HP, respectively. Samples of milk protein were hydrolysed with 6 M HCl, and then free amino acids were converted into butyl derivatives using HCl in butanol, followed by N-acylation using trifluoroacetic acid anhydride. The amino acid derivatives were analysed using a gas chromatograph equipped with a mass detector. 15N-excess after a six-day infusion of labelled urea was significantly higher (P < 0.05) in the vast majority of amino acids of milk protein from goats fed the LP diet in comparison with goats fed the HP diet. Therefore, the protein level of diets affects the incorporation of EUN into amino acids of milk protein. EUN was incorporated primarily into glutamic acid, methionine and arginine. At all levels of nitrogen in the diets, the incorporation of 15N into phenylalanine was very low.
Cechy publikacji
ORIGINAL_ARTICLE
Inne
System-identifier
626503
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