Amino acid exchange by the mammary gland of lactating goats when histidine limits milk production

B J Bequette, M D Hanigan, Alexander Graham Calder, C K Reynolds, Gerald Lobley, C MacRae

Research output: Contribution to journalArticle

80 Citations (Scopus)

Abstract

The aim of this study was to monitor amino acid (AA) exchange kinetics of the mammary gland in response to an imposed limitation on His supply for milk production. Lactating goats (n = 4, approximately 120 DIM) were fed a low protein ration that provided only 77% of metabolizable protein and 100% of energy requirements for milk production. The protein deficiency was alleviated by infusion into the abomasum of an AA mixture (67 g/d) including (+H; 4.4 g/d) or excluding (-H) His. Goats were assigned to treatments (6 to 7 d) according to a switchback design. On the last day of the first two periods, [U-13C]AA were continuously infused i.v. for 7 h and arterial and mammary vein blood was withdrawn to determine plasma AA concentration and enrichment. Flow probes monitored mammary blood flow. The secretion and enrichments of AA in milk casein were monitored each hour. A three-pool model of the gland was used to derive bi-directional rates of plasma AA exchange. Arterial plasma His concentration was lower during -H infusion (8 vs. 73 microM), but those of other AA changed little. Responses to low levels of plasma His were: 1) mammary blood flow increased by approximately 33%; 2) the gland's capacity to remove plasma His increased 43-fold, whereas the gland's capacity for other AA declined by two- to threefold; and 3) influx and efflux of His by the gland decreased. Thus, as the reduction in His efflux was insufficient to offset the reduced influx, milk protein yield decreased from 118 to 97 g/d.
Original languageEnglish
Pages (from-to)765-75
Number of pages11
JournalJournal of Dairy Science
Volume83
Issue number4
Publication statusPublished - 1 Apr 2000

Fingerprint

Human Mammary Glands
histidine
Histidine
Goats
mammary glands
milk production
Milk
goats
Amino Acids
amino acids
breasts
Breast
blood flow
blood veins
Abomasum
Protein Deficiency
protein deficiencies
milk protein yield
Milk Proteins
abomasum

Keywords

  • Amino Acids
  • Animals
  • Arteries
  • Blood Flow Velocity
  • Caseins
  • Dietary Proteins
  • Female
  • Goats
  • Histidine
  • Kinetics
  • Lactation
  • Mammary Glands, Animal
  • Milk
  • Veins

Cite this

Bequette, B. J., Hanigan, M. D., Calder, A. G., Reynolds, C. K., Lobley, G., & MacRae, C. (2000). Amino acid exchange by the mammary gland of lactating goats when histidine limits milk production. Journal of Dairy Science, 83(4), 765-75.

Amino acid exchange by the mammary gland of lactating goats when histidine limits milk production. / Bequette, B J; Hanigan, M D; Calder, Alexander Graham; Reynolds, C K; Lobley, Gerald; MacRae, C.

In: Journal of Dairy Science, Vol. 83, No. 4, 01.04.2000, p. 765-75.

Research output: Contribution to journalArticle

Bequette, BJ, Hanigan, MD, Calder, AG, Reynolds, CK, Lobley, G & MacRae, C 2000, 'Amino acid exchange by the mammary gland of lactating goats when histidine limits milk production' Journal of Dairy Science, vol. 83, no. 4, pp. 765-75.
Bequette, B J ; Hanigan, M D ; Calder, Alexander Graham ; Reynolds, C K ; Lobley, Gerald ; MacRae, C. / Amino acid exchange by the mammary gland of lactating goats when histidine limits milk production. In: Journal of Dairy Science. 2000 ; Vol. 83, No. 4. pp. 765-75.
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N2 - The aim of this study was to monitor amino acid (AA) exchange kinetics of the mammary gland in response to an imposed limitation on His supply for milk production. Lactating goats (n = 4, approximately 120 DIM) were fed a low protein ration that provided only 77% of metabolizable protein and 100% of energy requirements for milk production. The protein deficiency was alleviated by infusion into the abomasum of an AA mixture (67 g/d) including (+H; 4.4 g/d) or excluding (-H) His. Goats were assigned to treatments (6 to 7 d) according to a switchback design. On the last day of the first two periods, [U-13C]AA were continuously infused i.v. for 7 h and arterial and mammary vein blood was withdrawn to determine plasma AA concentration and enrichment. Flow probes monitored mammary blood flow. The secretion and enrichments of AA in milk casein were monitored each hour. A three-pool model of the gland was used to derive bi-directional rates of plasma AA exchange. Arterial plasma His concentration was lower during -H infusion (8 vs. 73 microM), but those of other AA changed little. Responses to low levels of plasma His were: 1) mammary blood flow increased by approximately 33%; 2) the gland's capacity to remove plasma His increased 43-fold, whereas the gland's capacity for other AA declined by two- to threefold; and 3) influx and efflux of His by the gland decreased. Thus, as the reduction in His efflux was insufficient to offset the reduced influx, milk protein yield decreased from 118 to 97 g/d.

AB - The aim of this study was to monitor amino acid (AA) exchange kinetics of the mammary gland in response to an imposed limitation on His supply for milk production. Lactating goats (n = 4, approximately 120 DIM) were fed a low protein ration that provided only 77% of metabolizable protein and 100% of energy requirements for milk production. The protein deficiency was alleviated by infusion into the abomasum of an AA mixture (67 g/d) including (+H; 4.4 g/d) or excluding (-H) His. Goats were assigned to treatments (6 to 7 d) according to a switchback design. On the last day of the first two periods, [U-13C]AA were continuously infused i.v. for 7 h and arterial and mammary vein blood was withdrawn to determine plasma AA concentration and enrichment. Flow probes monitored mammary blood flow. The secretion and enrichments of AA in milk casein were monitored each hour. A three-pool model of the gland was used to derive bi-directional rates of plasma AA exchange. Arterial plasma His concentration was lower during -H infusion (8 vs. 73 microM), but those of other AA changed little. Responses to low levels of plasma His were: 1) mammary blood flow increased by approximately 33%; 2) the gland's capacity to remove plasma His increased 43-fold, whereas the gland's capacity for other AA declined by two- to threefold; and 3) influx and efflux of His by the gland decreased. Thus, as the reduction in His efflux was insufficient to offset the reduced influx, milk protein yield decreased from 118 to 97 g/d.

KW - Amino Acids

KW - Animals

KW - Arteries

KW - Blood Flow Velocity

KW - Caseins

KW - Dietary Proteins

KW - Female

KW - Goats

KW - Histidine

KW - Kinetics

KW - Lactation

KW - Mammary Glands, Animal

KW - Milk

KW - Veins

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SP - 765

EP - 775

JO - Journal of Dairy Science

JF - Journal of Dairy Science

SN - 0022-0302

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ER -