THE CHANGES OF THE MILK QUANTITY AND QUALITY IN DAIRY COWS EXPOSED TO SOLAR RADIATION

DANA PUSTA, I. PAŞCA, R. MORAR

Abstract


in cows exposed to solar radiation during the hot summer days.The study was carried out in the period May-October 2000-2005 on groups of cows,belonging to Romanian Simental breed ,during the III-rd and IV-th lactation, breadin different conditions: on the pasture or in the stable.The determined parameters were: the total milk production to characterise the milkquantity and the milk quality was characterised by: electric conductivity, theprotein, the lactose, the fat content and the milk cells. These parameters werecorrelated with THI index during the summer days when it exceeds the value of 72,which is considered the limit of heat stress in cows.It was encountered a decreasing of the total milk production with 26.46% inAugust, compared to May (p<0.01) which was considered the reference month,when the cows started grazing. The reduced milk production is correlated with THIvalues, between them being established a reverse proportional variation.In cows exposed to sun it was recorded a reduction of the milk electric conductivitywith 12.42% compared to the values obtained in the morning, being reverseproportionally correlated with THI values. In cattle exposed to heat stress arerecorded changes in milk composition, meaning the reducing in fat content (12,97%,p<0,05) and in protein content (12,25%, p<0,05). The fat and the protein contentsvariations are close correlated with THI, between them being a reverse proportionalrelation. The number of the somatic cells in milk is growing in cows exposed tocaloric solar radiation, recording an increasing of 42.96% in August compared toMay. The increased number of somatic cells is directly correlated with THI.

Keywords


dairy cows; solar radiation; milk quantity and quality

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Scientific Papers Animal Science and Biotechnologies publish open access articles under the terms of the Creative Commons Attribution 4.0 Licence (read full legal code).


LUCRARI STIINTIFICE ZOOTEHNIE SI BIOTEHNOLOGII (SCIENTIFIC PAPERS ANIMAL SCIENCE AND BIOTECHNOLOGIES)

ISSN print 1841 - 9364
ISSN online 2344 - 4576
ISSN-L  1841 - 9364
(former ISSN 1221-5287, E-ISSN 1841-9364)

PUBLISHER: AGROPRINT Timisoara, Romania
PAPER ACCESS: Full text articles available for free
FREQUENCY: Semiannual
PUBLICATION LANGUAGE: English
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Banat´s University of Agricultural Sciences and Veterinary Medicine "King Michael I of Romania" from Timisoara
Bioengineering Faculty of Animal Resources
300645, Timişoara, Calea Aradului 119, Romania

E-mail: spasb [at] animalsci-tm.ro
Phone: +40-256-277160, Fax.: +40-256-277110