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Somatic cell counts: associated factors and relationship to production
Summary
Somatic cell counts in dairy cows increase with age and during summer months, peaking around 250 days in lactation. These counts are not significantly linked to milk production levels over a lactation period.
Area of Science:
- Animal Science
- Dairy Science
- Veterinary Epidemiology
Background:
- Somatic cell count (SCC) is a key indicator of udder health in dairy cattle.
- Understanding factors influencing SCC is crucial for dairy herd management and milk quality.
- Previous research has explored various factors, but comprehensive analysis across lactation and seasonal variations is ongoing.
Purpose of the Study:
- To investigate factors influencing somatic cell counts in dairy cows.
- To evaluate the association between somatic cell counts and milk production.
- To identify seasonal and age-related trends in somatic cell counts.
Main Methods:
- Utilized data from 748 Ontario Dairy Herd Improvement Corporation herds (1981-1983).
- Employed multiple curvilinear least squares regression on lactation summary and test day files (9406 Holsteins, 85,236 records).
- Analyzed natural logarithms of SCC and milk production, considering age and days in milk.
Main Results:
- Somatic cell count increased with age up to ~10 years, then decreased.
- No significant association found between "days in milk" and lactation average SCC.
- SCC showed a curvilinear relationship with days in lactation, peaking around 250 days.
- Highest SCC observed in summer, lowest in winter.
Conclusions:
- Age and season are significant factors influencing somatic cell counts in dairy cows.
- The relationship between days in lactation and SCC is curvilinear.
- Somatic cell count is not strongly associated with overall lactation milk production.