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Factors associated with colostral specific gravity in dairy cows
D E Morin1, P D Constable, F P Maunsell
1Department of Veterinary Clinical Medicine, University of Illinois, Urbana 61802, USA. d-morin@uiuc.edu
Journal of Dairy Science
|May 16, 2001
Summary
Colostral specific gravity in dairy cows is influenced by breed, lactation number, and calving month. This measurement better reflects colostral protein than IgG1, indicating potential limitations for assessing passive immunity.
Area of Science:
- Veterinary Medicine
- Animal Science
- Dairy Production
Background:
- Colostral quality is crucial for calf health and passive immunity transfer.
- Specific gravity is a commonly used, albeit imperfect, measure of colostrum quality.
Purpose of the Study:
- To identify factors affecting colostral specific gravity in dairy cows.
- To evaluate the correlation between colostral specific gravity and key colostral components (IgG1, protein, fat).
Main Methods:
- Measured specific gravity of 1085 first-milking colostrum samples from 608 cows across four breeds over five years.
- Analyzed effects of breed, lactation number, calving month/year, and nonlactating period length.
- Correlated specific gravity with colostral IgG1, protein, and fat concentrations in Holstein cows.
Main Results:
- Specific gravity varied significantly by breed (lower in Brown Swiss/Ayrshire) and lactation number (lower in first/second lactation).
- Calving month strongly impacted specific gravity, with highest values in autumn and lowest in summer.
- In Holstein cows, specific gravity correlated more strongly with protein (r=0.76) than IgG1 (r=0.53).
Conclusions:
- Colostral specific gravity is a better indicator of colostral protein concentration than IgG1 concentration.
- Month of calving is a significant factor influencing colostral specific gravity.
- Using specific gravity alone to assess IgG1 levels for passive immunity may have limitations.