Presence of pathogen DNA in milk harvested from quarters is associated to changes in cows’ milk yield and composition

Table 4 Pearson’s correlations^a (P ≤ 0.05) between udder health-related milk traits^b within each pathogen group^c

Trait	SCS	DSCC, %	DSCS	SCS	DSCC, %	DSCS
	Major, ≤ 2 quarters			Major, ≥ 3 quarters
DSCC, %	0.65			0.64
DSCS	0.99	0.73		0.99	0.73
Milk yield, kg/d	-0.19	ns	-0.17	-0.25	ns	-0.23
Fat, %	ns	ns	ns	ns	ns	ns
Protein, %	ns	-0.13	ns	ns	ns	ns
Casein, %	ns	-0.13	ns	ns	ns	ns
Casein index	ns	ns	ns	-0.21	-0.25	-0.22
Lactose, %	-0.34	ns	-0.31	-0.55	-0.23	-0.53
	Minor, ≤ 2 quarters			Minor, ≥ 3 quarters
DSCC, %	0.54			0.58
DSCS	0.98	0.69		0.99	0.68
Milk yield, kg/d	-0.38	ns	-0.35	-0.41	ns	-0.37
Fat, %	0.21	ns	0.18	0.35	ns	0.33
Protein, %	0.41	ns	0.35	0.47	ns	0.44
Casein, %	0.37	ns	0.32	0.44	ns	0.41
Casein index	-0.04	ns	-0.02	ns	ns	ns
Lactose, %	-0.45	ns	-0.39	-0.52	ns	-0.48
	Other, ≤ 2 quarters			Other, ≥ 3 quarters
DSCC, %	0.66			0.56
DSCS	0.99	0.76		0.98	0.69
Milk yield, kg/d	-0.49	ns	-0.44	-0.46	ns	-0.46
Fat, %	ns	ns	ns	ns	ns	ns
Protein, %	0.40	ns	0.34	ns	ns	ns
Casein, %	0.40	ns	ns	ns	ns	ns
Casein index	ns	ns	ns	-0.17	ns	ns
Lactose, %	-0.33	ns	-0.27	-0.48	ns	-0.43
	Pathogens absent
DSCC, %	0.49
DSCS	0.98	0.65
Milk yield, kg/d	-0.39	ns	-0.35
Fat, %	0.13	ns	0.12
Protein, %	0.30	ns	0.26
Casein, %	0.29	ns	0.25
Casein index	ns	ns	ns
Lactose, %	-0.30	0.16	-0.23

^ans Not significant
^bSCS Somatic cell score, calculated as SCS = 3 + log₂(SCC/100,000), where SCC is somatic cell count (cells/mL), DSCC Polymorphonuclear neutrophils and lymphocytes (%) out of the total SCC, DSCS Differential somatic cell score, calculated as DSCS = 3 + log₂(DSCC_N/100,000), where DSCC_N is the combined number of polymorphonuclear neutrophils and lymphocytes in milk (cells/mL)
^cDescription of groups is provided in Tables 1 and 2

ISSN: 1746-6148