Vitenskapelig artikkel

Genetic and environmental information in goat milk Fourier transform infrared spectra

Dagnachew, Binyam Sime; Kohler, Achim; Ådnøy, Tormod


Tidsskrift: Journal of Dairy Science (JDS), vol. 96, p. 3973–3985, 2013

Utgave: 6

Internasjonale standardnumre:
Trykt: 0022-0302
Elektronisk: 1525-3198

Open Access: none


Fourier transform infrared (FTIR) spectroscopy is
often used in prediction of major milk components in
genetic evaluation of dairy animals. Until now genetic
variability of goat milk FTIR spectra has only been
known indirectly through their contribution to the major
milk components. In this study, genetic and environmental
components of goat milk FTIR spectra were
examined directly. A data set containing 83,858 milk
FTIR spectral observations belonging to 29,320 Norwegian
dairy goats of 271 herds was used for the study.
Principal components analysis was applied on both
unprocessed and preprocessed spectral data, and new
traits (latent traits) were defined because a multitrait
analysis of all spectral variables for variance components
could not be done. Eight and 7 latent variables,
explaining approximately 99% of the total unprocessed
and preprocessed spectral variation, respectively, were
kept from the principal components analysis for genetic
analysis. Genetic and environmental variance components
were estimated for the latent traits using restricted
maximum likelihood. Genetic-to-total phenotypic
variance ratios (heritabilities) of the latent traits were
between 0.011 and 0.285 for the unprocessed spectra
and between 0.135 and 0.262 for the preprocessed spectra.
The estimated variance components for the latent
traits were back transformed to the spectral variables.
Heritabilities of these spectral variables ranged from
0.018 to 0.408 and variance ratios of the permanent
environmental effects of goats were between 0.002
and 0.184 of the phenotypic spectral variation. Highto-
moderate heritabilities were observed in particular
in spectral regions related to major milk components
(fat, lactose, and protein): between 1,030 and 1,300
cm−1, 1,500 and 1,600 cm−1, 1,700 and 1,800 cm−1, and
2,800 and 3,000 cm−1. Our results confirmed that a
substantial amount of genetic variation exists in goat
milk FTIR spectra. Not all spectral variations are of
genetic origin; some FTIR regions are highly influenced
by herd test-day variation. The study also pointed out
the possibility of using FTIR spectra as a monitoring
tool in herd management.
Key words: latent trait , principal components analysis
, Fourier transform infrared spectra , heritability