Effect of summer season on milk protein fractions in Holstein cows
Author(s)
Date Issued
2015
Type
article
Volume
98
Issue
98
Start Page
1815
End Page
1827
ISSN
15253198
220302
Journal
Abstract
Milk characteristics are affected by heat stress, but
very little information is available on changes of milk
protein fractions and their relationship with cheesemaking properties of milk. The main objective of the study
was to evaluate the effect of hot season on milk protein
fractions and cheesemaking properties of milk for Grana
Padano cheese production. The study was carried out
in a dairy farm with a cheese factory for transforming
the milk to Grana Padano cheese. The study was carried out from June 2012 to May 2013. Temperature and
relative humidity of the inside barn were recorded daily
during the study period using 8 electronic data loggers
programmed to record every 30 min. Constant managerial conditions were maintained during the experimental periods. During the experimental period, feed and
diet characteristics, milk yield, and milk characteristics
were recorded in summer (from June 29 to July 27,
2012), winter (from January 25 to March 8, 2013), and
spring (from May 17 to May 31, 2013). Milk yield was
recorded and individual milk samples were taken from
25 cows selected in each season during the p.m. milking. Content of fat, proteins, caseins (CN), lactose and
somatic cell count (SCC), titratable acidity, and milk
rennet coagulation properties were determined on fresh
samples. Milk protein fraction concentrations were determined by the sodium dodecyl sulfate-PAGE. Data
were tested for nonnormality by the Shapiro-Wilk test.
In case of nonnormality, parameters were normalized by
log or exponential transformation. The data were analyzed with repeated measures ANOVA using a mixed
model procedure. For all the main milk components
(fat, protein, total solids, and solids-not-fat), the lowest
values were observed in the summer and the greatest
values were observed in the winter. Casein fractions,
with the exception of γ-CN, showed the lowest values
in the summer and the greatest values in the winter.
The content of IgG and serum albumin was greater in
summer than in the winter and spring. A mild effect of season was observed for milk SCC, with greater values
in summer than in the winter and spring. A worsening
of milk coagulation properties was observed in summer season. The alteration of cheesemaking properties
during hot season seems strictly linked with changes of
milk protein fractions mainly with the decrease of αSCN and β-CN and the increase of undefined proteins.
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Conference(s)
JOURNAL OF DAIRY SCIENCE