Screening for phenotypic outliers identifies an unusually low concentration of a β-lactoglobulin B protein isoform in bovine milk caused by a synonymous SNP

Table 1 Milk composition by BLG genotype group

Milk component	BLG genotype group
Milk component	B'B' (n = 28)	BB (n = 64)	AA (n = 29)
Fat (g/L)	41.0 (4.0)	44.6 (3.1)	43.6 (4.2)
Crude protein (g/L)	34.9 (0.7)	34.9 (0.4)	35.2 (0.6)
True protein (g/L)	32.3 (0.7)	32.3 (0.4)	32.8 (0.6)
Lactose (g/L)	47.7 (0.4)	47.1 (0.4)	47.2 (0.6)
Casein (g/L)	27.4 (0.6)	27.0 (0.3)	27.2 (0.5)
Casein (% true protein)	0.85 (0.004)^a	0.84 (0.003)^b	0.83 (0.004)^c
β-lactoglobulin concentration. arb. units	24 (1.0)^a	46 (1)^b	83 (4)^c

Composite (am/pm) milk samples were collected from Friesian/Jersey crossbred cows of defined BLG genotype, in mid-lactation and major components analysed by mid infra-red spectroscopy. BLG was quantified by mass spectrometry and casein by wet chemistry. Figures in parentheses are standard errors of the mean (SEM). Significant differences (P < 0.05) among genotype groups, by analysis of variance, are indicated by differing letters in superscripts

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