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KMID : 1025520090510060537
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Journal of Animal Science and Technology
2009 Volume.51 No. 6 p.537 ~ p.542
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Seasonal and Regional Effects on Milk Composition of Dairy Cows in South Korea.
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Nam Ki-Taeg
Kim Ki-Hyun
Nam In-Sik
Oliver D. Abanto
Hwang Seong-Gu
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Abstract
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For a period of over 6 years, more than 160,000 milk samples were collected and analyzed to determine the influence of different seasonal temperatures and geographic regional location on milk composition in South Korea. Fat, protein, lactose, non fat milk solids(NFMS) and total solids(TS) contents were significantly higher among dairy cows milked in winter season than other seasons(p<0.05). In contrast, freezing point(FP), milk urea nitrogen(MUN) and somatic cell count(SCC) were significantly higher in summer season than other seasons (p<0.05). The average SCC in the autumn season was 358×103/ml, which was lower than any other seasons(p<0.05). These results may be due to the changes in temperature during different seasons. Meanwhile, milk produced by dairy cows in central region had higher fat, protein, lactose, NFMS, TS and MUN and had lower SCC compared to other regions(p<0.05). Fat, TS, FP, MUN and citric acid in northeast region were lower than other regions(p<0.05). The SCC was significantly higher in southeast region than those of other regions(p<0.05). As a result, it might be possible that the differences in feeding management in each different region may affect the milk composition. In conclusion, present results indicated that milk composition is clearly influenced by both season and regional location. Therefore, based on these results, development of different feeding systems, according to season and region is needed to produce high quality and satiable milk production.
South Korea has a moderate continental type of climate that is characterized with clear four different seasons of spring, autumn, cold winter, and hot and humid summer. The average temperature in January ranges from -3.6ºC in the extreme north to 2ºC in the southeast, and to 4.4ºC in southernmost region, Jea-ju Island. However, during the summer season, the average temperature especially in July ranges from 25ºC to 27ºC in the south down to 21ºC in the northeast. Daily temperatures during winter and summer seasons are highly fluctuating. The hot and humid summers brought by air pollution and East Asian monsoons are expected to extend for over six-month period of heat each year as a result of global climate change(The Government of the Republic of Korea, 2003).
Correspondingauthor:Ki Taeg Nam, School of Animal Life and Environmental Sciences, Hankyong National University, Anseong, 456-749, Republic of Korea. Tel: +82-31-670-5125, Fax: +82-31-670-5127 E-mail: ktnam@hknu.ac.kr
Holstein cows are more sensitive to the effects of heat stress than non-lactating cattle(Araki et al., 1984). High ambient temperature is indirectly related to the heat stress among dairy cows, thus, it is one of the major factors that can negatively affect milk yield and milk composition of dairy cows(Sharma et al., 1983; National Research Council, 1989). It has been well documented that heat stress due to exposure of dairy cows in high temperature results in a decreased dry matter(DM) intake (Coppock, 1978). Therefore, heat stress becomes major production challenge among dairy farmers in South Korea.
At present, around 60 million tons of raw milk is produced from around 7,000 dairy farms all over Korea. It has been known that changes of milk compositions are strongly influenced by nutritional management(Fuquay, 1981), genetic ability(Sharma et al., 1983), and climatic factors (Thatcher, 1974; Johnson, 1976). However, there is an apparent lack of information about seasonal and geographical changes on milk composition in Korea. The objective of this study was to analyze the influence of seasonal changes of temperatures and regional location on composition and quality of milk produced by dairy cows in South Korea.
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KEYWORD
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Milk composition, Seasonal variation, Regional difference, Dairy cow, South Korea
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