Milking-to-Milking Variability for Milk Yield, Fat and Protein Percentage, and Somatic Cell Count

The main objectives were to analyze milking-to-milking variability in milk yield, fat and protein percentages, and somatic cell count (SCC). Additional objectives were to investigate the factors that affect variation in milk fat percentage and to study the seasonal variations in milk, fat, and prote...

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Bibliographic Details
Published in:Journal of dairy science 2008-09, Vol.91 (9), p.3412-3423
Main Authors: Quist, M.A., LeBlanc, S.J., Hand, K.J., Lazenby, D., Miglior, F., Kelton, D.F.
Format: Article
Language:English
Subjects:
Animal productions
Animals
Biological and medical sciences
Cattle - physiology
Cell Count
dairy protein
Dairying
diurnal variation
Fats - analysis
feed management
Female
Food industries
Fundamental and applied biological sciences. Psychology
Lactation
Linear Models
Milk - chemistry
Milk - cytology
Milk - metabolism
milk analysis
Milk and cheese industries. Ice creams
milk fat
Milk Proteins - analysis
milk yield
milking
milking-to-milking variability
sampling
seasonal effect
seasonal variation
Seasons
somatic cell count
Surveys and Questionnaires
Terrestrial animal productions
Vertebrates
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Summary:The main objectives were to analyze milking-to-milking variability in milk yield, fat and protein percentages, and somatic cell count (SCC). Additional objectives were to investigate the factors that affect variation in milk fat percentage and to study the seasonal variations in milk, fat, and protein yields and SCC. A total of 16 farms (14 milked 2× and 2 milked 3×) across Canada participated in a 5-d milk-sampling study, with 27,328 milk samples collected and analyzed for fat and protein yields and SCC. Descriptive statistics for both 2× and 3× herds for milk yield and fat and protein percentages followed a typical pattern throughout lactation, and the somatic cell linear scores were higher in early lactation for first-lactation cows (4.7 vs. 3.8) but were higher at the end of lactation for cows in second lactation or greater (5.1 vs. 4.9). The 2× herds had higher milk yields in the morning (∼17 vs. ∼14kg), whereas the 3× herds had the lowest milk yields in the morning, and yields peaked at the evening milking (∼9 vs. ∼11.2kg). A herd management questionnaire was distributed to participating producers to investigate the relationship between management variables and variations in milk fat percentage over the 5-d sampling period. Data from the questionnaire determined that milking period had a significant effect on milk fat in 2× herds, with fat percentage 1.11% lower in the morning compared with the evening milking period. Seasonal differences in milk, fat, and protein yields were investigated in 910 cows on 3 farms, with 5,517 fat and 5,534 protein samples. The seasonal differences in fat yield [summer = 1.02±1.05kg/d (SEM); winter = 1.19±1.05kg/d] and protein yield (summer = 0.85±1.05kg/d; winter = 0.96±1.05kg/d) were significant only for first lactation. Understanding the variability in milk yield, fat and protein percentages, and SCC is important when making management decisions and in milk-recording programs.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.2007-0184