| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Animal Science, University of Arizona, Tucson 85721
2 Department of Animal and Veterinary Science, University of Idaho, Moscow 83844
3 Animal Agriculture Business, Monsanto Company, St. Louis, MO 63198
Corresponding author: R. J. Collier; e-mail: rcollier{at}ag.arizona.edu.
A dry period, typically 40 to 60 d, between lactations is believed to be required to maximize milk yield in the subsequent lactation. Several hypotheses have been proposed to explain the requirement for the dry period, including (1) replenishment of body reserves, (2) regeneration of mammary tissue, and (3) optimization of benefits from endocrine events near the time of parturition. Continuously milked cows or glands have depressed milk yields but no differences in mammary DNA content or cell number. Nutritional status and endocrine hormones are not factors in reduced milk yield in continuously milked glands. Data from continuous lactation studies suggest that depressed milk yields are due to reduced functionality of mammary parenchyma. There is a need to reevaluate effects of continuous lactation on milk yield in today’s high-producing dairy cow because studies on this topic were done using cows achieving peak milk production of 18 to 30 kg/d compared with 45 to 50 kg/d in today’s dairy cows. Another factor that has not been considered in conjunction with current milk production levels is the use of bovine somatotropin (bST). Supplementation with bST increases milk yield, improves lactation persistency, and may improve milk yield in continuously milked cows. Future research goals are to examine the effects of continuous lactation in high-producing cows and to determine the effects of bST on milk yield and mammary functionality in continuously milked cows.
Key Words: dry period length • management • mammary development • bovine somatotropin
Abbreviation key: CM = continuous milking, MEC = mammary epithelial cells, TGF-ß1 = transforming growth factor ß1
This article has been cited by other articles:
|
|
 |
|
  E. L. Annen, C. M. Stiening, B. A. Crooker, A. C. Fitzgerald, and R. J. Collier Effect of continuous milking and prostaglandin E2 on milk production and mammary epithelial cell turnover, ultrastructure, and gene expression J Anim Sci, May 1, 2008; 86(5): 1132 - 1144. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. C. Fitzgerald, E. L. Annen-Dawson, L. H. Baumgard, and R. J. Collier Evaluation of Continuous Lactation and Increased Milking Frequency on Milk Production and Mammary Cell Turnover in Primiparous Holstein Cows J Dairy Sci, December 1, 2007; 90(12): 5483 - 5489. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. H. Weng, C. J. Chang, W. Y. Chen, W. K. Chou, H. C. Peh, M. C. Huang, M. T. Chen, and H. Nagahata Contribution of somatic cell-associated activation of plasminogen to caseinolysis within the goat mammary gland. J Dairy Sci, June 1, 2006; 89(6): 2025 - 2037. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. Gulay, M. J. Hayen, H. H. Head, C. J. Wilcox, and K. C. Bachman Milk Production from Holstein Half Udders After Concurrent Thirty- and Seventy-Day Dry Periods J Dairy Sci, November 1, 2005; 88(11): 3953 - 3962. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. B. Andersen, T. G. Madsen, T. Larsen, K. L. Ingvartsen, and M. O. Nielsen The Effects of Dry Period Versus Continuous Lactation on Metabolic Status and Performance in Periparturient Cows J Dairy Sci, October 1, 2005; 88(10): 3530 - 3541. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
