Data/hora: 04/06/2024 02:23:41

Biblioteca(s): | Embrapa Caprinos e Ovinos.
Data corrente: | 28/01/1998
Data da última atualização: | 20/07/2023
Autoria: | BEQUETTE, B. J.; BACKWELL, F. R. C.; DHANOA, M. S.; WALKER, A.; CALDER, A. G.; WRAY-CAHEN, D.; METCALF, J. A.; SUTTON, J. D.; BEEVER, D. E.; LOBLEY, G. E.; MacRAE, J. C.
Título: | Kinetics of blood free and milk casein-amino acid labelling in the dairy goat at two stages of lactation.
Ano de publicação: | 1994
Fonte/Imprenta: | British Journal of Nutrition, v. 72, n. 2, p. 211-220, 1994.
Idioma: | Inglês
Conteúdo: | Abstract: The kinetics of blood free amino acids (AA) transfer into milk casein were compared in goats (n 4) at 61 (SE 5) d (Expt 1; post-peak, 4.51 (SE 0.26) kgmilk/d) and at 180 (SE 6) d (Expt 2; late, 2.36 (SE 0.16) kg &/d) of lactation during non-primed, continuous (Expt 1,12 h; Expt 2,16 h) intravenous infusions of mixtures of ~-[l-'~C]leucine and ~-[l-'~C]phenylalanine with either ~-(l-'~C]valine (Expt 1) or ~-[5-'~C]methionine (Expt 2). The I3C enrichments of blood free and casein-bound AA were fitted to a single exponential model to estimate isotopic plateaux and the fractional rate constant for milk casein labelling. Milk protein output and its contribution to whole-body flux was higher in Expt 1 (post-peak) than in Expt 2 (late lactation), but the kinetics of 13C labelling of the casein-bound AA were similar for all AA tracers in both experiments. At both stages of lactation the delay (6-8 h) between the attainment of isotopic plateau for the blood free AA and the corresponding attainment of plateau for the caseinbound AA indicated that the blood free pool was not the immediate precursor pool for milk casein biosynthesis. Plateau enrichments of casein-bound AA were generally higher than those for the corresponding blood free AA in both experiments. These results indicate that the relative contributions of different AA sources to the immediate precursor pool for milk casein biosynthesis are similar at different stages of lactation despite major changes in the partitioning of whole-body flux towards milk protein output. Non-milk protein fluxes were also similar in post-peak and late lactation.
Thesagro: | Aminoácido; Caprino; Caseína; Lactação.
Thesaurus Nal: | Amino acids; Casein; Dairy goats; Lactating females.
Categoria do assunto: | L Ciência Animal e Produtos de Origem Animal
Registro original: | Embrapa Caprinos e Ovinos (CNPC)
Exemplares: | CNPC - (10013-1) - ADD - AP - DD -  -  -  - DIS