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Relationships of somatic cell count with milk lactose and protein over the first 10 days postpartum in dairy cows.

H. Peterson

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06-22-2020

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Abstract:

M83
Relationships of somatic cell count with milk lactose and protein over the first 10 days postpartum in dairy cows.
H. Peterson*1, T. Kelley1, J. Williams1, W. Price3, E. Peterson4, M. McGuire2, M. McGuire1. 1Animal and Veterinary Sciences, University of Idaho Moscow, ID, 2Margaret Ritchie School of Family and Consumer Sciences, University of Idaho Moscow, ID, 3Statistical Programs, College of Agricultural and Life Sciences, University of Idaho Moscow, ID, 4Erik L. Peterson Dairy Filer, ID.

There is little research examining the relationships of somatic cell count (SCC) with lactose and protein concentrations in bovine milk. Understanding these relationships may provide insight into how animal health is related to milk composition and quality. The objective of this study was to examine the relationships of SCC and lactose and protein in bovine milk in the first 10 d postpartum. Quarter-milk samples were collected daily from 107 cows on 4 dairies and milk components assessed by near-infrared analysis. Data were analyzed using a mixed linear regression model with SCC (log-transformed) and day postpartum as independent variables and dairy as a random variable while assuming a compound symmetric correlation structure for the repeated measures of day within quarter of each cow. Milk type was characterized as colostrum (d0; C), transitional milk (d1-d4; TM), and mature milk (d5-d10; MM). Lactose concentrations were 3.16 � 0.03%, 4.08 � 0.01%, and 4.32 � 0.01% in C, TM, and MM, respectively; protein concentrations were 9.40 � 0.10%, 3.94 � 0.03%, and 3.03 � 0.01% in C, TM, and MM, respectively. The range of SCC across all samples was 1,000 to 9,999,000 cells/mL. In C, there was no relationship between SCC and lactose, but there was a negative relationship between SCC and protein (P = 0.0004). For TM and MM, there was a negative relationship between SCC and lactose that became more negative as days postpartum progressed. There was a positive relationship between SCC and protein in TM; conversely, there was a negative relationship between these variables in MM. For both TM and MM, protein decreased with increasing days postpartum. These results suggest relationships of SCC with lactose and protein exist; however, they are not consistent over time.

Keywords: dairy cow, milk, somatic cell count.