Short communication: Relationship between the efficiency of utilization of feed nitrogen and 15N enrichment in casein from lactating dairy cows

ARJ Cabrita, AJM Fonseca, RJ Dewhurst

Research output: Contribution to journalArticleResearchpeer-review

6 Citations (Scopus)

Abstract

The objective of the present study was to evaluate the relationship between the efficiency of conversion of feed N into milk N [N-use efficiency (NUE)] and 15N enrichment of milk casein from lactating cows fed corn silage-based diets. Samples of feeds and milk were obtained from 3 experiments with lactating dairy cows. All diets were based on corn silage and were designed to evaluate the effects of (1) diets with different ratios of effective rumen-degradable protein to fermentable metabolizable energy (experiment 1), (2) different proportions of quickly and slowly rumen-degradable protein (experiment 2), and (3) synchronizing the availability of fermentable metabolizable energy and effective rumen- degradable protein in the rumen (experiment 3). Although no significant effect of diet on casein δ15N values was detected, casein was more enriched than the diet in each of the experiments. Nitrogen-use efficiency was negatively related to adjusted Δ15N (casein δ15N − diet δ15N) for experiments 1 and 2 individually and when combining data from all 3 experiments. The relatively low values for Δ15N suggest that these productive animals were using dietary N efficiently, with a high proportion of N going to milk protein and less to urea. The weak, although significant, relationship between NUE and adjusted Δ15N, is consistent with relatively little variation in hepatic deamination and transamination, with variation in rumen efficiency having the predominant effect on NUE. The present study confirms the lower 15N enrichment in protein when NUE is high and the potential to use N-isotope fractionation as a marker of NUE.
Original languageEnglish
Pages (from-to)7225 - 7229
Number of pages5
JournalJournal of Dairy Science
Volume97
Issue number11
DOIs
Publication statusFirst published - 2014

Fingerprint

animal communication
casein
rumen
feed conversion
dairy cows
nitrogen
diet
milk
proteins
transamination
isotope fractionation
deamination
dairy protein
corn silage
metabolizable energy
silage
urea
cows
liver
sampling

Bibliographical note

1028921

Keywords

  • Dairy cow
  • Feed efficiency
  • Isotopic fractionation
  • Nitrogen-15

Cite this

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abstract = "The objective of the present study was to evaluate the relationship between the efficiency of conversion of feed N into milk N [N-use efficiency (NUE)] and 15N enrichment of milk casein from lactating cows fed corn silage-based diets. Samples of feeds and milk were obtained from 3 experiments with lactating dairy cows. All diets were based on corn silage and were designed to evaluate the effects of (1) diets with different ratios of effective rumen-degradable protein to fermentable metabolizable energy (experiment 1), (2) different proportions of quickly and slowly rumen-degradable protein (experiment 2), and (3) synchronizing the availability of fermentable metabolizable energy and effective rumen- degradable protein in the rumen (experiment 3). Although no significant effect of diet on casein δ15N values was detected, casein was more enriched than the diet in each of the experiments. Nitrogen-use efficiency was negatively related to adjusted Δ15N (casein δ15N − diet δ15N) for experiments 1 and 2 individually and when combining data from all 3 experiments. The relatively low values for Δ15N suggest that these productive animals were using dietary N efficiently, with a high proportion of N going to milk protein and less to urea. The weak, although significant, relationship between NUE and adjusted Δ15N, is consistent with relatively little variation in hepatic deamination and transamination, with variation in rumen efficiency having the predominant effect on NUE. The present study confirms the lower 15N enrichment in protein when NUE is high and the potential to use N-isotope fractionation as a marker of NUE.",
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Short communication: Relationship between the efficiency of utilization of feed nitrogen and 15N enrichment in casein from lactating dairy cows. / Cabrita, ARJ; Fonseca, AJM; Dewhurst, RJ.

In: Journal of Dairy Science, Vol. 97, No. 11, 2014, p. 7225 - 7229.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Short communication: Relationship between the efficiency of utilization of feed nitrogen and 15N enrichment in casein from lactating dairy cows

AU - Cabrita, ARJ

AU - Fonseca, AJM

AU - Dewhurst, RJ

N1 - 1028921

PY - 2014

Y1 - 2014

N2 - The objective of the present study was to evaluate the relationship between the efficiency of conversion of feed N into milk N [N-use efficiency (NUE)] and 15N enrichment of milk casein from lactating cows fed corn silage-based diets. Samples of feeds and milk were obtained from 3 experiments with lactating dairy cows. All diets were based on corn silage and were designed to evaluate the effects of (1) diets with different ratios of effective rumen-degradable protein to fermentable metabolizable energy (experiment 1), (2) different proportions of quickly and slowly rumen-degradable protein (experiment 2), and (3) synchronizing the availability of fermentable metabolizable energy and effective rumen- degradable protein in the rumen (experiment 3). Although no significant effect of diet on casein δ15N values was detected, casein was more enriched than the diet in each of the experiments. Nitrogen-use efficiency was negatively related to adjusted Δ15N (casein δ15N − diet δ15N) for experiments 1 and 2 individually and when combining data from all 3 experiments. The relatively low values for Δ15N suggest that these productive animals were using dietary N efficiently, with a high proportion of N going to milk protein and less to urea. The weak, although significant, relationship between NUE and adjusted Δ15N, is consistent with relatively little variation in hepatic deamination and transamination, with variation in rumen efficiency having the predominant effect on NUE. The present study confirms the lower 15N enrichment in protein when NUE is high and the potential to use N-isotope fractionation as a marker of NUE.

AB - The objective of the present study was to evaluate the relationship between the efficiency of conversion of feed N into milk N [N-use efficiency (NUE)] and 15N enrichment of milk casein from lactating cows fed corn silage-based diets. Samples of feeds and milk were obtained from 3 experiments with lactating dairy cows. All diets were based on corn silage and were designed to evaluate the effects of (1) diets with different ratios of effective rumen-degradable protein to fermentable metabolizable energy (experiment 1), (2) different proportions of quickly and slowly rumen-degradable protein (experiment 2), and (3) synchronizing the availability of fermentable metabolizable energy and effective rumen- degradable protein in the rumen (experiment 3). Although no significant effect of diet on casein δ15N values was detected, casein was more enriched than the diet in each of the experiments. Nitrogen-use efficiency was negatively related to adjusted Δ15N (casein δ15N − diet δ15N) for experiments 1 and 2 individually and when combining data from all 3 experiments. The relatively low values for Δ15N suggest that these productive animals were using dietary N efficiently, with a high proportion of N going to milk protein and less to urea. The weak, although significant, relationship between NUE and adjusted Δ15N, is consistent with relatively little variation in hepatic deamination and transamination, with variation in rumen efficiency having the predominant effect on NUE. The present study confirms the lower 15N enrichment in protein when NUE is high and the potential to use N-isotope fractionation as a marker of NUE.

KW - Dairy cow

KW - Feed efficiency

KW - Isotopic fractionation

KW - Nitrogen-15

U2 - 10.3168/jds.2014-8297

DO - 10.3168/jds.2014-8297

M3 - Article

VL - 97

SP - 7225

EP - 7229

JO - Journal of Dairy Science

JF - Journal of Dairy Science

SN - 0022-0302

IS - 11

ER -