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Effects of continuous lactation and short dry periods on mammary function and animal health

Published online by Cambridge University Press:  12 December 2011

R. J. Collier ,
E. L. Annen-Dawson  and
A. Pezeshki
R. J. Collier*
Affiliation:
Department of Animal Science, University of Arizona, Tucson 85719, USA
E. L. Annen-Dawson
Affiliation:
Oord Dairy, LLC, Sunnyside, WA 98944, USA
A. Pezeshki
Affiliation:
Physiology and Biometrics, Ghent University, Ghent, Belgium
*
†Email: rcollier@ag.arizona.edu
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Abstract

The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period.

Keywords

dry periodmammary glandmammary cellhealthmilk yield
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animal , Volume 6 , Issue 3: 61th EAAP Annual Meeting, 2010, Heraklion, Greece: 10th International Workshop on Biology of Lactation in Farm Animals (BOLFA) and Session “Evolution of mammary gland and milk secretion: consequences for lactation in farm animals” , 27 January 2012 , pp. 403 - 414
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Copyright © The Animal Consortium 2011

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