Factor	Season of calving (number of samples)
	Spring (92)		Summer (93)		Fall (89)		Winter (91)		P-value
	LSM¹	SEM²	LSM	SEM	LSM	SEM	LSM	SEM	P-value
Volume, L	7.7		7.1		6.5		6.8
IgG, mg/ml	23.3^c	1.52	41.2^b	1.49	23.8^c	1.81	50.8^a	1.57	0.001
IgM, mg/ml	6.1^b	0.36	5.4^b	0.44	2.97^c	0.37	8.4^a	0.38	<0.0001
Fat, %	4.2	0.3	4.8	0.4	4.6	0.3	4.6	0.3	0.15
Protein, %	18.1	0.5	18.9	0.6	18.7	0.5	18.8	0.5	0.22
Lactose, %	1.8^b	0.1	1.8^b	0.1	2.1^a	0.1	2.0^ab	0.1	0.05
Total solid, %	27.9	0.6	27.2	0.6	28.4	0.7	27	0.6	0.06
Ca, mg/kg	2443^b	95.2	3086^a	109.2	2629^b	96.2	2694^b	100.2	0.0002
P, mg/kg	1906^b	78.8	2200^a	90.4	1833^b	79.7	1731^b	83.3	0.001