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Pakistan Journal of Nutrition 7 (1): 161-164, 2008
ISSN 1680-5194
© Asian Network for Scientific Information, 2008
161
The Effect of Seasonal Variation on the Composition of Cow Milk in Van Province
Elvan Ozrenk and Sebnem Selcuk Inci
1 2
Department of Food Engineering, Faculty of Agriculture, University of Yuzuncu Yil, 65080, Van, Turkey
1
Ministry of Agriculture and Rural Affairs, Laboratories of Food Control, Van, Turkey
2
Abstract: The research was performed to investigate the effects of seasonal variation on changing of cow
milk components in Van province. A total of 160 cow milk samples were collected and examined from
January to August of 2001. These were obtained from 12 different local points of the Van province in Turkey.
The research was carried out in two periods. The first period was the winter period covering January-
February-March months and the second one was the summer period covering June-July-August months.
Samples were collected according to season, so that milk samples could be taken from the cows which had
been fed with hay in born in winter period (January-February-March) and from those which had been fed with
green grass on the Pasteur in the area in summer period. According to the results paired t test, the fat
content and titratable acidity of winter and summer periods have been found significantly at p<0.05 level.
Seasonal variation effect was found significantly on the protein content rate and total solids, fat, titratable
acidity respectively levels of p<0.05 and p<0.01.
Key words: Seasonal variation, milk composition, cow milk
Introduction
The variation in milks and milk yield within a species
depends on so many factors. Some of these factors are
genetics, stage of lactation, daily variation, parity, type of
diet, age, udder health and season (Kilic and Kilic, 1994;
Haenlein, 2003). The process ability and quality of milk
products such as cheese, butter are influenced
significantly by these factors (Lindmark and Mansson,
2000; 2003; Barron et al., 2001).
District, climatic conditions and lactation periods are
known as seasonal changes which have influences on
the milk composition. Especially, there is a negative
correlation between environmental temperature and the
amount of milk fat and protein. When temperature is
increased the solid fat tends to decrease. Ng-Kwai-
Hang et al. (1984) and Lacroix et al. (1996) have
reported that percentage of fat, protein, casein and all
the fraction of nitrogen have been influenced by the
seasonal variations. Sevi et al. (2001) found high
ambient temperatures to adversely affect the yield and
the cheese-making properties of milk by increasing the
clotting time and the rate of clot formation and
decreasing clot firmness. The light-to-dark ratio can also
induce marked changes in milk yield and composition
(Casati et al., 1998). In fact, a high light-to-dark ratio
leads to a reduction in fat and protein contents of milk,
probably as a consequence of a greater secretion of
prolactin whose concentration in plasma is higher in the
summer than in the winter (Tucker, 1989). Lactation
period moved forward progressing and when the
environmental heat degree increased, the fat content
decreased (Kilic and Kilic, 1994; Sekerden, 1999;
Yetismeyen, 2000).
Some studies show that the amount of short chain fatty
acids in milk varies significantly with season. It has been
found highest in the summer and lowest value in the
winter. Some investigators showed that the amount of "-
tocopherol raised along with the winter months to
summer months (Lindmark and Mansson, 2003; Lock
and Garnsworthy, 2003). Also, it has also been found
that seasonal climatic changes may affect the
abundance of volatile compounds. In winter and spring
the terpenes’ are not the most important class in the
note of milk. These compounds reached important
quantity only in the summer (Fedele et al., 2005).
A lot of researchers realized about different breeds and
region of cow milk composition in Turkey (Arslan and
Ermis, 2000; Ozdemir et al., 2000; Dogan et al., 2002).
In this research the important region of Van province
according to milk yield, milk products, plants cover and
geographic location have been selected. The aim of this
study is to determine the composition of cow’s milk and
to find out the effect of seasonal variation on this
composition.
Materials and Methods
The cow’s milk samples were supplied from different 12
local point of the Van province. These local points are
Van city central, Edremit, Gurpinar, Muradiye, Catak,
Bahcesaray, Baskale, Ozalp, Caldiran, Ercis, Gevas and
Saray regions.
The research was carried out in two periods. The first
period was the winter period covering January-February-
March months and the second one was the summer
period covering June-July-August months. In the first
step 80 milk samples had been taken regularly from 12
Ozrenk and Selcuk Inci: Effect of Seasonal Variation on the Composition of Cow Milk
162
Table 1: Some general chemical and physical characteristics of cows’ milk obtained from Van province
Total solid Fat Non fat Protein Titratable Specific Minerals
(%) (%) solid (%) (%) acidity (%) pH gravity (%)
Period I Minimum 9.9317 2.4 6.7984 2.432 0.20 5.77 1.028 0.711
Maximum 12.6236 3.7 9.1136 3.717 0.36 6.73 1.035 0.892
Average±Sx 11.5064±1.023 3.1±0.683 8.4064±0.989 2.868±0.814 0.26±0.053 6.50±0.205 1.031±0.004 0.802±0.106
aa c ba c
Period II Minimum 7.5161 1.3 5.3161 2.239 0.15 5.75 1.030 0.751
Maximum 12.6298 3.5 9.5056 3.708 0.37 6.74 1.039 1.026
Average±Sx 10.8683±1.841 2.3±0.938 8.5683±1.701 2.794±0.944 0.21±0.080 6.50±0.472 1.032±0.003 0.841±0.160
aa c ba c
General Average±Sx 11.1874±1.432 2.7±0.811 8.4874±1.345 2.831±0.879 0.24±0.066 6.50±0.339 1.032±0.004 0.822±0.133
:Important at the level of p<0.01, :Important at the level of p<0.05, :According to t-test important at the level of p<0.05
a b c
locals points in winter. In the second step the other 80The more pronounced seasonal variation was due to
milk samples had been collected from the same 12outdoor grazing in summer and bar feeding in winter.
local points and totally 160 samples of cows milk wereThere were many important differences between the
analyzed. feeds composition which were given to animals during
Samples were collected according to season, so thatthese two periods (Yetismeyen, 2000). Probably due to
milk samples could be taken from the cows which hadthe fact that the feed diet was based on hay during the
been fed with hay in born in winter period (January-winter months the herbage was not available. Increased
February-March) and from those which had been fedfeeding frequency of low fiber, high grain diets increase
with green grass on the Pasteur in the area in summermilk fat levels (Waldner et al., 2005). The similar variable
period. For each period 80 sample was collected andamount of milk fat has been observed in the sheep milk.
totally 160 samples of cows milk were analyzed. The percentage of milk fat has increased from February
Cow’s milk samples were collected directly fromto June and then it has decreased gradually. This
homogenized bulk milk at determined local points andvariation has been affected by the feeding and lactation
put in to the 200 ml sterile plastic container stored at(Mendia et al., 2000). Isiklar and Kurdal (1999) have
4EC and immediately transported frigidly to thedeclared that the fat content of milk has been marketed
laboratory and analyzed. in Bursa city is 3.30 %. According to Kovacs et al. (1999)
Total solids, fat, non fat solids, protein, minerals,the fat content of Hungarian Grey cattle has been found
titratable acidity and specific gravity of milk samplesas 4.94%. Lindmark et al. (2003) have reported that the
were determined as described by Kurt et al. (2003). fat content of Swidish dairy milk is 4.34%. Similar results
pH value of samples were determined according to thewere obtained for Elazig/Turkey dairy milk by Arslan and
method proposed by Kosikowski (1982) and Case et al.Ermis (2000). The obtained results were appropriate for
(1985) using Hana Inst. 8521 pH-meter. TS 1018 Turkish raw milk standard (Anonymous, 1981).
Statistical analysis were performed using SAS packageThe mean protein content of the cows’ milk was 2.868 %
program (Anonymous, 1997). for winter period and 2.794% for summer period. It was
Results and Discussion
Table 1 gives means of data from physico-chemical
analysis of cows’ milk composition and statistical
analyses.
It can be seen from Table 1 that milk fat, protein and total
solids percentages were the highest during the winter
and the lowest during the summer.
According to the results paired t test, the fat content of
winter and summer periods has been found significantly
at p<0.05 level.
Milk fat was the most variable component among the
milk contents. The amount of fat in milk composition
was affected by a lot of factors. The seasonal variation
and lactation period were the important factors among
them. In the lactating cow, seasonal variations have
been observed for milk protein content and to a lesser
extent, for the milk fat content. This might ascribe a high
light-to-dark ratio leading to a reduction in fat and protein
contents of milk, probably as a consequence of a greater
secretion of prolactin whose concentration in plasma is
higher in the summer than in winter (Sevi et al., 2004).
determined that the protein content of milk showed
changes along the year. The differences between the
two periods has been found significant statistically
(p<0.05). Generally milk protein percentage is positively
correlated with the milk fat percentage. If one is high, the
other is usually high. It reduces in milk fat and protein
concentration as a result of hot weather. Generally, milk
protein does not fluctuate as much as milk fat.
The mean total solid does content of the cows’ milk was
11.1874 ± 1.432%. There were differences statistically
between winter and summer periods (p<0.01). Because
of hot weather, high humidity decrease and dry matter
intake, it decreased in the summer. Different
researchers have reported that the solid content of
Brown-Swiss in Kirsehir was 11.936% averagely (Dogan
et al., 2002), in Swiss was 13% (Lindmark-Mansson et
al., 2003) and cows milk in Ankara 11.18 % (Sezgin and
Kocak, 1982). It is possible to say that there is a
similarity between these mean values and the results
obtained from this study.
The first acidity in milk is due to the amount of casein
phosphate, citrate and carbondioxide. But then at the
Ozrenk and Selcuk Inci: Effect of Seasonal Variation on the Composition of Cow Milk
163
end of the bacterial activity the lactic acid was formedArslan, M. and H. Ermis, 2000. Analysis of milks in
and the acidity of milk increased. The extra acidity value
in milk is not desirable (Kurt et al., 2003). It has been
explained in The Turkish Food Regulation that the acidity
of cows’ milk is not more than 8 SH (0.18 %). It can be
seen from Table 1, that is higher than the normal value.
However Turkish dairy milk acidity values have changed
between 4.20 SH (0.09%) and 12 SH (0.27%) (Sezgin
and Kocak, 1982; Isiklar and Kurdal, 1991; Kurt et al.,
2003). Similar results were obtained in this research
and seasonal variation has been found significant
statistically (p<0.05).
Conclusions: The composition of Van dairy milk and its
contents determined in this research were in agreement
with other studies’ results. It was determined that the fat
content of Van cows’ milk have been affected importantly
by the seasonal changes. However the other contents of
milk was not affected significantly by this factor.
According to the results obtained in this study, it is
possible to say that when the milk fat content was
higher, protein and total solid contents were also higher
and that milk fat, protein and total solid percentages
were the highest during the winter and the lowest during
the summer. This result correspond to the data given in
the literature. Seasonal patterns in the production of
milk, fat and protein have been described in different
countries and under different management practices. In
the northern hemisphere, the lowest protein and fat
percentages occur in the summer months (June-
August), and the highest percentage occur between
October and December (Sargeant et al., 1998). For this
reason during the summer season, strategies for
reducing the impact of high heat loads on lactating
cows, such as shading, increased ventilation, changing
the time of feeding to the late afternoon, and an
appropriate administration of mineral elements with the
feed rations are necessary to prevent deterioration of
cheese yield and quality.
Nutrition can be regarded as one of the most important
sources of variation in the yield and composition of milk,
but climatic conditions and seasonal variation and
regional differences can also play an important role.
Also the quality and the composition of the milk are of
the most importance to the dairy industry and human
health because milk composition is related to milk
process ability. When the milk has higher protein content
it should be processed to cheese. If it has higher level
fat, then it should be used to produce butter.
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