Genetic variability of lactoferrin content estimated by mid-infrared spectrometry in bovine milk

The effects of lactoferrin (LF) on the immune system
have already been shown by many studies. Unfortunately,
the current methods used to measure LF levels
in milk do not permit the study of the genetic variability
of lactoferrin or the performance of routine genetic evaluations.
The first aim of this research was to derive a
calibration equation permitting the prediction of LF in
milk by mid-infrared spectrometry (MIR). The calibration
with partial least squares on 69 samples showed
a ratio of standard error of cross-validation to standard
deviation equal to 1.98. Based on this value, the calibration
equation was used to establish an LF indicator
trait (predicted LF; pLF) on a large number of milk
samples (n = 7,690). A subsequent study of its variability
was conducted, which confirmed that stage of lactation
and lactation number influence the overall pLF
level. Small differences in mean pLF among 7 dairy
breeds were also observed. The pLF content of Jersey
milk was significantly higher than that in Holstein
milk. Therefore, the choice of breed could change the
expected LF level. Heritability estimated for pLF was
19.7%. The genetic and phenotypic correlations between
somatic cell score and pLF were 0.04 and 0.26,
respectively. As somatic cell score increases in presence
of mastitis, this observation seems to indicate that pLF,
or a function of observed pLF, compared with expected
LF might have potential as an indicator of mastitis.
The negative genetic correlation (−0.36) between milk
yield and pLF could indicate an undesirable effect of
selection for high milk production on the overall LF
level.