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The effect of intramammary infection with coagulase-negative staphylococci in early lactating heifers on milk yield throughout first lactation revisited

Sofie Piepers UGent, Ynte Hein Schukken, Pieter Passchyn UGent and Sarne De Vliegher UGent (2013) JOURNAL OF DAIRY SCIENCE. 96(8). p.5095-5105
abstract
The objective of this study was to further scrutinize the previously found positive association between intramammary infection (IMI) caused by coagulase-negative staphylococci (CNS) in early lactating heifers and test-day daily milk yield (MY) throughout first lactation, with a specific focus on the effect of the heifers' genetically determined milk production levels and the incidence of clinical mastitis. Two precise longitudinal data sets were analyzed using a series of statistical models including potential confounding and intermediate variables. The final database included the IMI status at calving, composite milk somatic cell count (SCC) and MY records at test day up to 285 d in milk (DIM), farmer-recorded clinical mastitis (CM) cases between 14 and 285 DIM, estimated new IMI incidence based on a SCC threshold of 100,000 cells/mL between 14 and 285 DIM, DIM, average 305-d MY at the herd level, and the heifers' genetic merit for MY from 240 dairy heifers from 29 dairy herds. Seventy-one (29.6%) early lactating heifers were noninfected, 108 heifers (45.0%) were CNS infected, and 61 heifers (25.4%) were infected with any major pathogen. The positive effect of CNS IMI in early lactation on test-day MY was estimated at 1.32 kg/d using a first basic mixed regression model. Correcting for the confounder genetic merit for MY reduced this effect to 1.17 kg. Interestingly, taking into account the confounding effect of herd resulted in an increase of the estimate from 1.32 to 2.2 kg/d. The positive effect of CNS IMI in early lactation on MY after correcting the model for both confounders was estimated at 2.05 kg/d. Heifers infected with CNS in the first DIM tended to have fewer CM cases throughout lactation compared with the noninfected herd mates. Including the intermediate variable CM in the model explained 0.16 kg/d of the corrected effect of 2.05 kg/d. Inclusion of test-day SCC, another intermediate variable, however, increased the estimate by 0.11 kg/d. With an appropriate correction for several confounders and biologically understood intermediate variables such as CM, test-day SCC, and new IMI based on SCC threshold of 100,000 cells/mL, an unexplained test-day MY difference between CNS-infected and noninfected heifers of 2.0 kg/d remained.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
heifer, coagulase-negative staphylococci, intramammary infection, milk yield, SOMATIC-CELL COUNT, CLINICAL MASTITIS, DAIRY HEIFERS, RISK-FACTORS, ENVIRONMENTAL MASTITIS, UDDER HEALTH, COWS, IMPACT, HERD, PATHOGENS
journal title
JOURNAL OF DAIRY SCIENCE
J. Dairy Sci.
volume
96
issue
8
pages
5095 - 5105
Web of Science type
Article
Web of Science id
000322055900032
JCR category
AGRICULTURE, DAIRY & ANIMAL SCIENCE
JCR impact factor
2.55 (2013)
JCR rank
2/52 (2013)
JCR quartile
1 (2013)
ISSN
0022-0302
DOI
10.3168/jds.2013-6644
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
4173312
handle
http://hdl.handle.net/1854/LU-4173312
date created
2013-10-28 15:21:16
date last changed
2016-12-19 15:42:47
@article{4173312,
  abstract     = {The objective of this study was to further scrutinize the previously found positive association between intramammary infection (IMI) caused by coagulase-negative staphylococci (CNS) in early lactating heifers and test-day daily milk yield (MY) throughout first lactation, with a specific focus on the effect of the heifers' genetically determined milk production levels and the incidence of clinical mastitis. Two precise longitudinal data sets were analyzed using a series of statistical models including potential confounding and intermediate variables. The final database included the IMI status at calving, composite milk somatic cell count (SCC) and MY records at test day up to 285 d in milk (DIM), farmer-recorded clinical mastitis (CM) cases between 14 and 285 DIM, estimated new IMI incidence based on a SCC threshold of 100,000 cells/mL between 14 and 285 DIM, DIM, average 305-d MY at the herd level, and the heifers' genetic merit for MY from 240 dairy heifers from 29 dairy herds. Seventy-one (29.6\%) early lactating heifers were noninfected, 108 heifers (45.0\%) were CNS infected, and 61 heifers (25.4\%) were infected with any major pathogen. The positive effect of CNS IMI in early lactation on test-day MY was estimated at 1.32 kg/d using a first basic mixed regression model. Correcting for the confounder genetic merit for MY reduced this effect to 1.17 kg. Interestingly, taking into account the confounding effect of herd resulted in an increase of the estimate from 1.32 to 2.2 kg/d. The positive effect of CNS IMI in early lactation on MY after correcting the model for both confounders was estimated at 2.05 kg/d. Heifers infected with CNS in the first DIM tended to have fewer CM cases throughout lactation compared with the noninfected herd mates. Including the intermediate variable CM in the model explained 0.16 kg/d of the corrected effect of 2.05 kg/d. Inclusion of test-day SCC, another intermediate variable, however, increased the estimate by 0.11 kg/d. With an appropriate correction for several confounders and biologically understood intermediate variables such as CM, test-day SCC, and new IMI based on SCC threshold of 100,000 cells/mL, an unexplained test-day MY difference between CNS-infected and noninfected heifers of 2.0 kg/d remained.},
  author       = {Piepers, Sofie and Schukken, Ynte Hein and Passchyn, Pieter and De Vliegher, Sarne},
  issn         = {0022-0302},
  journal      = {JOURNAL OF DAIRY SCIENCE},
  keyword      = {heifer,coagulase-negative staphylococci,intramammary infection,milk yield,SOMATIC-CELL COUNT,CLINICAL MASTITIS,DAIRY HEIFERS,RISK-FACTORS,ENVIRONMENTAL MASTITIS,UDDER HEALTH,COWS,IMPACT,HERD,PATHOGENS},
  language     = {eng},
  number       = {8},
  pages        = {5095--5105},
  title        = {The effect of intramammary infection with coagulase-negative staphylococci in early lactating heifers on milk yield throughout first lactation revisited},
  url          = {http://dx.doi.org/10.3168/jds.2013-6644},
  volume       = {96},
  year         = {2013},
}

Chicago
Piepers, Sofie, Ynte Hein Schukken, Pieter Passchyn, and Sarne De Vliegher. 2013. “The Effect of Intramammary Infection with Coagulase-negative Staphylococci in Early Lactating Heifers on Milk Yield Throughout First Lactation Revisited.” Journal of Dairy Science 96 (8): 5095–5105.
APA
Piepers, S., Schukken, Y. H., Passchyn, P., & De Vliegher, S. (2013). The effect of intramammary infection with coagulase-negative staphylococci in early lactating heifers on milk yield throughout first lactation revisited. JOURNAL OF DAIRY SCIENCE, 96(8), 5095–5105.
Vancouver
1.
Piepers S, Schukken YH, Passchyn P, De Vliegher S. The effect of intramammary infection with coagulase-negative staphylococci in early lactating heifers on milk yield throughout first lactation revisited. JOURNAL OF DAIRY SCIENCE. 2013;96(8):5095–105.
MLA
Piepers, Sofie, Ynte Hein Schukken, Pieter Passchyn, et al. “The Effect of Intramammary Infection with Coagulase-negative Staphylococci in Early Lactating Heifers on Milk Yield Throughout First Lactation Revisited.” JOURNAL OF DAIRY SCIENCE 96.8 (2013): 5095–5105. Print.