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KMID : 1025520040460030335
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Journal of Animal Science and Technology
2004 Volume.46 No. 3 p.335 ~ p.346
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Environmental and Physiological Factors on Milk Yields and Compositions of Holstein Cows in Korea
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Han K. J.
Ahn Jong-Ho
Lee Deuk-Hwan
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Abstract
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Factors associated with milk urea nitrogen on milk yield and milk composition were investigated in this study regarding feeding management and physiological status of lactating cows. The data for 3 years between 1999 and 2002 for this study were collected from 129,645 cows by Korean Agricultural Cooperatives Federation. The objectives of this study were to describe the relationships between milk urea concentrations and seasonal factors, cow factors and production of milk, milk fat, protein and somatic cell score(SCS). Milk urea was highest in summer and it also showed a nonlinear association with milk yield. Milk yield was higher at milk urea concentrations of 21～24mg/dl, however it decreased at higher level of milk urea concentrations than 24mg/dl. Milk urea was higher with increased parities of cows and in particular, at 3 to 4 parities. There was a negative association between milk urea and SCS in milk. SCS in milk was lowest at milk urea concentrations of 21～24mg/dl. Milk fat and milk protein were greatly affected by days in milk(DIM), year of birth, season and milk urea concentrations, respectively. While milk urea increased in summer, milk fat and protein were decreased. Milk protein decreased according to longer days in milk. With regard to the influences of parity, milk protein in overall was negatively correlated to milk urea in all lactations, however the extent of decrease of milk protein at high concentrations of milk urea was bigger at third lactation. The balanced supply of energy and protein to the animals might have greatly affected the urea concentrations and protein content of milk.
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KEYWORD
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MUN, FCM, Lactation, Seasonal effects, SCS, Milk protein
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